chore: release v0.10.0

Terrain pass now ports the SAGE water model (Ocean.fx / OpenSAGE Water.frag): a de-gridded procedural wave normal combined with the retail ra3_deepocean flow and ra3_deepocean_nrm bump maps (appended as the last two terrain-atlas layers, no new backend binding), Schlick fresnel, sky reflection + depth-graded refraction, SAGE diffuse/specular lighting, depth-based transparency, and an underwater tint (UnderwaterDeferred.fx). Mirrored across terrain.frag / dx_terrain.hlsl / webgl_terrain_frag.glsl / webgpu_terrain.wgsl.

Also: logs move to the per-user state dir (%LOCALAPPDATA%\\OpenRA3\\logs, else XDG) and archive as openra3.<stamp>.log; the FPS label shows the active backend; middle-drag camera reset; objects and roads below the water plane are culled.

CMakeLists.txt

@@ -26,7 +26,7 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 set(CMAKE_CXX_SCAN_FOR_MODULES ON)
 
-project(OpenRA3 VERSION 0.8.0 LANGUAGES C CXX)
+project(OpenRA3 VERSION 0.9.0 LANGUAGES C CXX)
 
 if(NOT CMAKE_BUILD_TYPE AND NOT CMAKE_CONFIGURATION_TYPES)
     set(CMAKE_BUILD_TYPE Release CACHE STRING "Build type" FORCE)
@@ -196,6 +196,25 @@ target_sources(ra3_enderlog PUBLIC FILE_SET CXX_MODULES FILES third_party/libend
 target_compile_features(ra3_enderlog PUBLIC cxx_std_26)
 openra3_target_defaults(ra3_enderlog)
 
+# --- RA3 built-in asset containers (vendored libra3assets) --------------------
+# Reader/writer for the files the retail game ships: `BIG4` archives, the EA
+# RefPack codec, SAGE `.csf` string tables and `.map` (`CkMp`) containers, plus
+# the compiled `BinaryAsset` streams. A sibling of libenderlog: C++26 modules
+# (`import ra3.assets;`) importing the standard library. It owns the on-disk
+# format knowledge, so `ra3.fs` / `ra3.map` / `ra3.terrain` become thin adapters.
+add_library(ra3_assets STATIC)
+target_sources(ra3_assets PUBLIC FILE_SET CXX_MODULES FILES
+    third_party/libra3assets/src/assets.cppm
+    third_party/libra3assets/src/error.cppm
+    third_party/libra3assets/src/bytes.cppm
+    third_party/libra3assets/src/refpack.cppm
+    third_party/libra3assets/src/big.cppm
+    third_party/libra3assets/src/binary.cppm
+    third_party/libra3assets/src/csf.cppm
+    third_party/libra3assets/src/map.cppm)
+target_compile_features(ra3_assets PUBLIC cxx_std_26)
+openra3_target_defaults(ra3_assets)
+
 # --- engine core -------------------------------------------------------------
 add_library(ra3_core STATIC)
 target_sources(ra3_core PUBLIC FILE_SET CXX_MODULES FILES src/core/ra3.core.cppm)
@@ -225,16 +244,16 @@ target_sources(ra3_game PUBLIC FILE_SET CXX_MODULES FILES src/game/ra3.game.cppm
 target_link_libraries(ra3_game PUBLIC ra3_core ra3_logic)
 openra3_target_defaults(ra3_game)
 
-# --- filesystem: BIG4 + RefPack ---------------------------------------------
+# --- filesystem: BIG4 + RefPack (adapter over libra3assets) -------------------
 add_library(ra3_fs STATIC)
 target_sources(ra3_fs PUBLIC FILE_SET CXX_MODULES FILES src/fs/ra3.fs.cppm)
-target_link_libraries(ra3_fs PUBLIC ra3_core)
+target_link_libraries(ra3_fs PUBLIC ra3_core ra3_assets)
 openra3_target_defaults(ra3_fs)
 
 # --- map discovery/loading ---------------------------------------------------
 add_library(ra3_map STATIC)
 target_sources(ra3_map PUBLIC FILE_SET CXX_MODULES FILES src/map/ra3.map.cppm)
-target_link_libraries(ra3_map PUBLIC ra3_core ra3_fs)
+target_link_libraries(ra3_map PUBLIC ra3_core ra3_fs ra3_assets)
 openra3_target_defaults(ra3_map)
 
 # --- minimal skirmish simulation --------------------------------------------
@@ -252,7 +271,7 @@ openra3_target_defaults(ra3_render)
 # --- real map terrain (HeightMapData / BlendTileData) ------------------------
 add_library(ra3_terrain STATIC)
 target_sources(ra3_terrain PUBLIC FILE_SET CXX_MODULES FILES src/terrain/ra3.terrain.cppm)
-target_link_libraries(ra3_terrain PUBLIC ra3_core ra3_fs ra3_render)
+target_link_libraries(ra3_terrain PUBLIC ra3_core ra3_fs ra3_render ra3_assets)
 openra3_target_defaults(ra3_terrain)
 
 # --- map static art (compiled W3D meshes) ------------------------------------
@@ -580,3 +599,15 @@ add_executable(ra3_tests tests/ra3_tests.cpp)
 target_link_libraries(ra3_tests PRIVATE ra3)
 openra3_target_defaults(ra3_tests)
 add_test(NAME ra3_tests COMMAND ra3_tests)
+
+# libra3assets' own dependency-free unit tests (RefPack + BIG4 + BinaryAsset +
+# CSF + CkMp round-trips), built against the vendored copy so the upstream
+# suite keeps guarding the readers OpenRA3 now relies on.
+add_executable(ra3assets_unit
+    third_party/libra3assets/tests/test_main.cpp
+    third_party/libra3assets/tests/test_assets.cpp)
+target_include_directories(ra3assets_unit PRIVATE third_party/libra3assets/tests)
+target_link_libraries(ra3assets_unit PRIVATE ra3_assets)
+target_compile_features(ra3assets_unit PRIVATE cxx_std_26)
+openra3_target_defaults(ra3assets_unit)
+add_test(NAME ra3assets_unit COMMAND ra3assets_unit)

README.md

@@ -243,14 +243,17 @@ wixl 0.106 has no arm64 support, so Windows/ARM64 ships the portable `.zip`
 
 ## Logging
 
-Every run writes `openra3.log` next to the executable through the vendored
+Every run writes `openra3.log` in a per-user `logs/` folder — on Windows
+`%LOCALAPPDATA%\OpenRA3\logs`, elsewhere `$XDG_STATE_HOME/openra3/logs`
+(falling back to `~/.local/state/openra3/logs`) — created on first use and kept
+out of the binary's own directory, through the vendored
 [`libenderlog`](third_party/libenderlog) module (`import ender.log;`). A file
-sink archives the previous log to `openra3.log.<YYYYmmdd-HHMMSS>` on open, so
+sink archives the previous log to `openra3.<YYYYmmdd-HHMMSS>.log` on open, so
 each run gets its own file; the active file rotates at 4 MiB and the last 10
 archives are kept. Records at **`warn` and above** carry a call stack (Windows
 `CaptureStackBackTrace` / POSIX `execinfo`, because libc++ has no
-`<stacktrace>`). A hard crash also writes `openra3_crash.log` with the faulting
-module and a raw backtrace.
+`<stacktrace>`). A hard crash also writes `openra3_crash.log` alongside it with
+the faulting module and a raw backtrace.
 
 ## Running a skirmish
 

VERSION

@@ -1 +1 @@
-0.8.0
+0.10.0

apps/openra3/main.cpp

@@ -10,14 +10,56 @@ import ender.log;
 
 namespace {
 #if defined(_WIN32)
-    /** Path of the crash report written next to the executable. */
-    [[nodiscard]] auto crash_log_path() -> const std::filesystem::path & {
-        static const auto path = [] {
-            std::wstring buffer(32768U, L'\0');
-            const DWORD length = GetModuleFileNameW(nullptr, buffer.data(), static_cast<DWORD>(buffer.size()));
-            buffer.resize(length);
-            return std::filesystem::path{buffer}.parent_path() / L"openra3_crash.log";
+    /** `%LOCALAPPDATA%` as a wide path, or empty when the variable is unset. */
+    auto local_appdata() -> std::filesystem::path {
+        const DWORD needed = GetEnvironmentVariableW(L"LOCALAPPDATA", nullptr, 0U);
+        if (needed == 0U || needed > 32768U) return {};
+        std::wstring buffer(needed, L'\0');
+        const DWORD written = GetEnvironmentVariableW(L"LOCALAPPDATA", buffer.data(), needed);
+        if (written == 0U || written >= needed) return {};
+        buffer.resize(written);
+        return std::filesystem::path{buffer};
+    }
+#endif
+
+    /**
+     * Directory that holds per-run logs and crash reports: a `logs` folder
+     * under the platform's per-user state location, created on first use. It
+     * deliberately does not sit beside the executable, which may be read-only
+     * or a shared build tree.
+     *
+     * Windows: `%LOCALAPPDATA%\OpenRA3\logs`; elsewhere
+     * `$XDG_STATE_HOME/openra3/logs` (falling back to
+     * `~/.local/state/openra3/logs`).
+     */
+    [[maybe_unused]] auto log_directory() -> const std::filesystem::path & {
+        static const auto directory = [] {
+#if defined(_WIN32)
+            auto base = local_appdata();
+            if (base.empty()) base = std::filesystem::temp_directory_path();
+            base /= L"OpenRA3";
+#else
+            std::filesystem::path base;
+            if (const char *state = std::getenv("XDG_STATE_HOME"); state != nullptr && *state != '\0')
+                base = state;
+            else if (const char *home = std::getenv("HOME"); home != nullptr && *home != '\0')
+                base = std::filesystem::path{home} / ".local" / "state";
+            else
+                base = std::filesystem::temp_directory_path();
+            base /= "openra3";
+#endif
+            auto result = base / "logs";
+            std::error_code ec;
+            std::filesystem::create_directories(result, ec);
+            return result;
         }();
+        return directory;
+    }
+
+#if defined(_WIN32)
+    /** Path of the crash report, under the per-user `logs` folder. */
+    [[nodiscard]] auto crash_log_path() -> const std::filesystem::path & {
+        static const auto path = log_directory() / L"openra3_crash.log";
         return path;
     }
 
@@ -92,7 +134,7 @@ namespace {
      * timestamped file on open, so every run gets its own log and the previous
      * run's log is preserved.
      */
-    auto setup_logging(const std::filesystem::path &exe_dir) -> void {
+    auto setup_logging() -> void {
         namespace log = ender::log;
         log::configure({.minimum = log::level::info, .stacktrace_from = log::level::warn});
 #if defined(__EMSCRIPTEN__)
@@ -100,9 +142,8 @@ namespace {
         // console.error regardless of level; use stdout so INFO/WARN appear at
         // their real level. There is no file sink on the web.
         log::set_sinks({std::make_shared<log::console_sink>(std::cout)});
-        (void) exe_dir;
 #else
-        log::add_file_sink(exe_dir / "openra3.log", {.max_file_size = 4U * 1024U * 1024U, .max_archives = 10U});
+        log::add_file_sink(log_directory() / "openra3.log", {.max_file_size = 4U * 1024U * 1024U, .max_archives = 10U});
 #endif
         log::info("OpenRA3 started");
     }
@@ -190,6 +231,32 @@ namespace {
         return maps;
     }
 
+    /** Case-insensitive ASCII ordering (`a` before `b`). */
+    auto name_less(std::string_view a, std::string_view b) -> bool {
+        const auto length = std::min(a.size(), b.size());
+        for (std::size_t i = 0; i < length; ++i) {
+            const auto ca = static_cast<unsigned char>(std::tolower(static_cast<unsigned char>(a[i])));
+            const auto cb = static_cast<unsigned char>(std::tolower(static_cast<unsigned char>(b[i])));
+            if (ca != cb) return ca < cb;
+        }
+        return a.size() < b.size();
+    }
+
+    /**
+     * Order the map list the way the retail skirmish screen does: alphabetically
+     * by the localized display name (e.g. "Battlebase Beta" before "Cabana
+     * Republic"), falling back to the id for entries with equal names.
+     */
+    auto sort_maps_by_name(std::vector<asset_map> &maps, const ra3::map::map_name_table &names) -> void {
+        std::sort(maps.begin(), maps.end(), [&](const asset_map &a, const asset_map &b) {
+            const auto name_a = names.lookup(a.id);
+            const auto name_b = names.lookup(b.id);
+            if (name_less(name_a, name_b)) return true;
+            if (name_less(name_b, name_a)) return false;
+            return a.id < b.id;
+        });
+    }
+
     /** Find `<id>_art.tga` anywhere under `root`. */
     auto find_art(const std::filesystem::path &root, std::string_view id) -> std::optional<std::filesystem::path> {
         const auto want = std::string{id} + "_art.tga";
@@ -259,14 +326,18 @@ namespace {
             }
             const auto world_w = terrain.world_width();
             const auto world_h = terrain.world_height();
+            // An opaque water surface hides anything below it, so cull objects
+            // and roads submerged under the map's water plane (sunken ships,
+            // underwater props, ...) instead of drawing them on top of the sea.
+            const auto cull_below_z = terrain.has_water ? terrain.water_plane_z : -3.4e38F;
             scene = ra3::models::build_scene(stream, placements, [&](float x, float y) -> float {
                 if (x < 0.0F || y < 0.0F || x >= world_w || y >= world_h) return 0.0F;
                 const auto cx = std::min(terrain.width - 1U, static_cast<ra3::core::uint32>(x / ra3::terrain::cell_size));
                 const auto cy = std::min(terrain.height - 1U, static_cast<ra3::core::uint32>((world_h - y) / ra3::terrain::cell_size));
                 return static_cast<float>(terrain.elevation(cx, cy)) * options.z_scale;
-            });
-            std::printf("objects: %zu placed, %zu missing, %zu road segments, %zu triangles, %zu textures (%s)\n", scene.placed, scene.missing,
-                        scene.roads, scene.triangle_count(), scene.textures.size(), paths->bin.filename().string().c_str());
+            }, 128U, cull_below_z);
+            std::printf("objects: %zu placed, %zu missing, %zu hidden, %zu road segments, %zu triangles, %zu textures (%s)\n", scene.placed, scene.missing,
+                        scene.hidden, scene.roads, scene.triangle_count(), scene.textures.size(), paths->bin.filename().string().c_str());
         } catch (const std::exception &error) {
             std::printf("objects: failed to build scene (%s)\n", error.what());
         }
@@ -410,8 +481,9 @@ namespace {
 
     auto command_maps(const std::filesystem::path &assets) -> int {
         if (!ensure_assets(assets)) return 1;
-        const auto maps = list_asset_maps(assets);
+        auto maps = list_asset_maps(assets);
         const auto names = ra3::map::load_map_names(assets);
+        sort_maps_by_name(maps, names);
         std::printf("maps: %zu\n", maps.size());
         for (const auto &m: maps) {
             std::error_code ec;
@@ -424,8 +496,9 @@ namespace {
     auto command_skirmish(const std::vector<std::string> &args, const std::filesystem::path &assets) -> int {
         using namespace ra3;
         if (!ensure_assets(assets)) return 1;
-        const auto maps = list_asset_maps(assets);
+        auto maps = list_asset_maps(assets);
         if (maps.empty()) return 1;
+        sort_maps_by_name(maps, map::load_map_names(assets));
         const auto requested = option_value(args, "--map");
         const asset_map *picked = &maps.front();
         if (requested) {
@@ -463,8 +536,10 @@ namespace {
     auto command_render(const std::vector<std::string> &args, const std::filesystem::path &assets) -> int {
         using namespace ra3;
         if (!ensure_assets(assets)) return 1;
-        const auto maps = list_asset_maps(assets);
+        auto maps = list_asset_maps(assets);
         if (maps.empty()) return 1;
+        const auto names = map::load_map_names(assets);
+        sort_maps_by_name(maps, names);
         const auto requested = option_value(args, "--map");
         const asset_map *picked = &maps.front();
         if (requested) {
@@ -473,7 +548,6 @@ namespace {
         }
 
         render::scene_options scene;
-        const auto names = map::load_map_names(assets);
         scene.title = "OpenRA3 - " + names.lookup(picked->id);
         if (const auto size = option_value(args, "--world-size")) scene.world_width = scene.world_height = std::stod(*size);
 
@@ -1141,7 +1215,9 @@ namespace {
 
         const bool want_gpu = s.mode == 0 && s.out.empty() && s.thumbnail == false;
         if (want_gpu) {
-            view.gpu = terrain::build_gpu_terrain(view.map, view.textures, {}, [&](float t) { report(0.70F + 0.18F * t, "Building terrain..."); });
+            report(0.62F, "Loading objects...");
+            const auto objects = build_object_scene(assets, map_file.stem().string(), view.map, terrain::render_options{}, bytes);
+            view.gpu = terrain::build_gpu_terrain(view.map, view.textures, {}, objects, [&](float t) { report(0.70F + 0.18F * t, "Building terrain..."); });
             if (!starts.empty()) {
                 view.camera3d.target_x = starts[0].x;
                 view.camera3d.target_y = starts[0].y;
@@ -1185,12 +1261,13 @@ namespace {
 
     auto command_menu(const std::vector<std::string> &args, const std::filesystem::path &assets) -> int {
         if (!ensure_assets(assets)) return 1;
-        const auto maps = list_asset_maps(assets);
+        auto maps = list_asset_maps(assets);
         if (maps.empty()) {
             std::puts("no maps found");
             return 1;
         }
         const auto names = ra3::map::load_map_names(assets);
+        sort_maps_by_name(maps, names);
 
         menu_state st;
         // Seed the menu from any command-line flags so they are all visible/editable.
@@ -1307,8 +1384,9 @@ namespace {
     /** Render one menu frame to a BMP (headless preview of the menu layout). */
     auto command_menu_preview(const std::vector<std::string> &args, const std::filesystem::path &assets) -> int {
         if (!ensure_assets(assets)) return 1;
-        const auto maps = list_asset_maps(assets);
+        auto maps = list_asset_maps(assets);
         const auto names = ra3::map::load_map_names(assets);
+        sort_maps_by_name(maps, names);
         menu_state st;
         if (const auto requested = option_value(args, "--map")) {
             for (std::size_t i = 0; i < maps.size(); ++i) {
@@ -1338,7 +1416,7 @@ auto main(int argc, char **argv) -> int {
     const std::vector<std::string> args{argv + 1, argv + argc};
     const auto exe_dir = executable_dir(argc > 0 ? argv[0] : ".");
     const auto assets = exe_dir / "assets";
-    setup_logging(exe_dir);
+    setup_logging();
 #if defined(__EMSCRIPTEN__)
     // The wasm build runs on a Web Worker (its runtime's main thread lives
     // there), where synchronous XHR is legal, so the asset tree is mounted

docs/ARCHITECTURE.md

@@ -533,7 +533,8 @@ Mirrors SAGE `GameEngine/Common`. Everything else speaks this.
   - `[ ]` pass scheduling, barriers, transient/aliased resources `(v0.6)`
 - **F3 Terrain render** `[~]`
   - `[x]` top-down software + GPU heightfield with blend ramp + gutter atlas
-  - `[ ]` perspective terrain mesh, LOD, cliff, water `(v0.6)`
+  - `[ ]` perspective terrain mesh, LOD, cliff `(v0.6)`
+  - `[x]` water surface in the raymarch: SAGE `Water.frag` port (ocean/river) `[~]`
 - **F4 Model render** `[~]`
   - `[x]` static map-object triangle soup, world-space, depth-tested over the terrain (Vulkan + software)
   - `[x]` bind-pose skinning (bone-space vertices) + ground-decal depth bias
@@ -550,8 +551,35 @@ Mirrors SAGE `GameEngine/Common`. Everything else speaks this.
   - `[x]` ARGB framebuffer, blit/line/circle/text, TGA decode, BMP encode
   - `[x]` map compositing, grid, markers; headless output
 - **F9 Post-processing** `[ ]`
+  - `[x]` underwater tint/fog in the terrain pass (retail `UnderwaterDeferred.fx`) `[~]`
   - `[ ]` bloom, color grading, AA, resolution scaling `(v0.7)`
 
+### M16b shader porting status (retail `Data\Shaders.big` → `*.fxo`)
+
+The retail set is **88 compiled effects** (`Core12\shaders\compiled`, duplicated
+in `Misc`/`Shaders`; `Core5`/`Core8` ship only `terrain`; plus a 60-byte
+`null` stub). OpenRA3 implements the static-map subset only:
+
+- **Ported (approximate stand-ins, shared by all backends):** `Terrain.fx`
+  (`terrain.*`), the opaque diffuse subset of `BuildingsGeneric.fx` /
+  `BasicW3D.fx` / `ObjectsGeneric.fx` (`object.*`), and the SAGE water model
+  `Ocean.fx` (+ `OceanDisplacement`/`OceanNoVertexTexture`/`RiverWater`/
+  `RiverReflection`/`UnderwaterDeferred`, folded into the `terrain.*` water
+  branch — see `docs/REVERSE_ENGINEERING.md`). The retail water flow and bump
+  maps (`art/terrain/ra3_deepocean.tga`, `ra3_deepocean_nrm.tga`) ride as the
+  last two terrain-atlas layers, so no backend adds a binding.
+- **Not ported:** all faction/variant model shaders (`buildings*`, `objects*`,
+  `basicw3d*`, `defaultw3d*`, `normalmapped`, `tree`/`treesway`), instances/
+  animation (`infantry*`), particles and beams (`cpuparticle`, `gpuparticle*`,
+  `swarmparticle`, `laser*`, `lightning`, `fx*`, `tracer`, `trail`,
+  `connectionline`, `linerenderers`, `stream`, `rain`, `simple*`), shadows and
+  ground decals (`shadow`, `decal`, `outlines`, `occlusion`, `terraintracks`),
+  post-processing (`postfx_*`), and the 2D/misc shaders (`render2d`, `video`,
+  `bootupscreen`, `debug`, `errormissing`, `rotateenvironmentmap`,
+  `distortingobject`). The shared retail includes `shadowmap.fxh`, `ssao.fxh`,
+  `macrotexture.fxh`, `gamma.fxh` are likewise absent (`skinning.fxh` is done at
+  bind pose only).
+
 ### M17 `ra3.ui` — platform layer & backends `[D]`
 
 - **F1 Display abstraction** `[D]`

docs/REVERSE_ENGINEERING.md

@@ -324,6 +324,48 @@ vertex color and `TintColor`; `basicw3d.fxo` instead modulates a single
 macro/lightmap with `(vertexColor + additive) * diffuse * 2` and has no normal
 map. (Recovered by disassembling the embedded `vs_3_0`/`ps_3_0` bytecode.)
 
+### Water / ocean (`Ocean.fx`, `OceanDisplacement.fx`, `RiverWater.fx`, `UnderwaterDeferred.fx`)
+
+The SAGE water surface is reconstructed by OpenSAGE as
+`Assets/Shaders/Water.vert`+`Water.frag` (same family as retail `Ocean.fx`). The
+surface is a world-space mesh drawn with alpha blending, fed by two render
+targets rendered before it: a **reflection** map (scene from the mirrored camera
+about `GlobalWaterSettings.ReflectionPlaneZ`) and a **refraction** map + depth.
+The fragment model (`Water.frag`) is:
+
+- `waterUV = worldPos.xy / 320`; a scrolling `WaterTexture` supplies both a
+  flow distortion (`(tex.xy*2-1)*0.05`) and the flow layer; a `BumpTexture`
+  supplies the surface `worldNormal`.
+- `fresnelFactor = dot(viewVector, +Z)`; reflection/refraction are sampled in
+  screen space (`gl_FragCoord / ViewportSize`), each displaced by the distortion.
+- `linearWaterDepth = linearize(RefractionDepth) - linearize(gl_FragCoord.z)`;
+  `alpha = clamp((linearWaterDepth/2)/TransparentWaterDepth, 0, TransparentWaterMinOpacity)`.
+- `final = diffuseColor * textureColor * cloudColor`, then mixed with
+  `mix(reflectionColor, refractionColor, fresnelFactor)` (both maps on) or just
+  one of them, per `IsRenderReflection` / `IsRenderRefraction`.
+- Per-time-of-day `WaterSet`: `WaterTexture`, `UScrollPerMS`/`VScrollPerMS`,
+  `DiffuseColor`, `TransparentDiffuseColor`; `WaterTransparency` supplies
+  `TransparentWaterDepth`/`TransparentWaterMinOpacity`, the skybox faces,
+  `RiverTransparencyMultiplier`, `ReflectionPlaneZ`/`ReflectionOn`.
+
+OpenRA3 has no water mesh or reflection/refraction targets (its terrain is
+raymarched), so the model is folded into the terrain pass (`shaders/terrain.frag`
+and its HLSL/GLSL-ES/WGSL twins): the ray's water-plane hit takes a scrolling
+wave normal built from the retail bump map combined with a de-gridded procedural
+wave, Schlick fresnel (F0 = 0.02), a sky reflection and a depth-graded
+refraction, SAGE diffuse + specular lighting, a depth-based transparency fade,
+and — when the camera is below `ReflectionPlaneZ` — an underwater tint/fog
+(`UnderwaterDeferred.fx`). The two retail maps
+`art/terrain/ra3_deepocean.tga` (flow/distortion) and `ra3_deepocean_nrm.tga`
+(bump normal) are appended as the **last two layers of the terrain atlas**
+(`ra3::terrain::build_gpu_terrain`, `water_flow = layer_count - 2`,
+`water_normal = layer_count - 1`), so every backend samples them with the
+existing atlas binding; absent maps fall back to a neutral layer. True
+reflection/refraction render targets are still the next step.
+`GPUParticleOceanDisplacement.fx` drives wave displacement from a GPU particle
+buffer and has no analogue here.
+
+
 The map's `ObjectsList` chunk is a list of nested `Object` assets —
 `Coord3D`, Z `angle`, `RoadType` u32, a `u16`-prefixed type-name and a property
 list whose keys index the shared name table (`ra3.map::parse_objects`). Each

shaders/dx_terrain.hlsl

@@ -8,6 +8,10 @@
 // `Terrain.fx` / OpenSAGE `Terrain.frag` do, so it never restarts at a cell
 // edge; material boundaries cross-fade with the SAGE blend ramp.
 //
+// The water plane is shaded with a port of the SAGE water effect
+// (`Ocean.fx` / OpenSAGE `Water.frag`); the camera-below-water tint stands in
+// for `UnderwaterDeferred.fx`. See docs/REVERSE_ENGINEERING.md.
+//
 // The Vulkan push constants (20 floats) become a constant buffer.
 
 cbuffer TerrainCB : register(b0) {
@@ -15,7 +19,7 @@ cbuffer TerrainCB : register(b0) {
     float4 params;  // x=pitch, y=fov, z=water_z, w=has_water
     float4 sun;     // xyz=sun dir, w=ambient
     float4 mapinfo; // x=W, y=H, z=unused, w=z_scale
-    float4 misc;    // x=time, y=unused, z=cells per texture repeat, w=aspect
+    float4 misc;    // x=time, y=water kind (0=ocean,1=river), z=cells per repeat, w=aspect
 };
 
 Texture2D<float> heightmap : register(t0);
@@ -27,6 +31,12 @@ SamplerState atlas_smp : register(s2);
 
 static const float CELL = 10.0; // must match ra3::terrain::cell_size
 
+// SAGE water model constants (see docs/REVERSE_ENGINEERING.md).
+static const float WATER_SCALE = 1.0 / 320.0;
+static const float WATER_TRANSPARENT_DEPTH = 10.0;
+static const float WATER_MIN_OPACITY = 0.70;
+static const float WATER_RIVER_MULTIPLIER = 1.0;
+
 struct VSOut {
     float4 pos : SV_Position;
     float2 uv : TEXCOORD0;
@@ -104,6 +114,105 @@ float3 sample_layer(uint layer, float wx, float wy) {
     return atlas.Sample(atlas_smp, float3(float2(wx, wy) / span, l)).rgb;
 }
 
+// ---- SAGE water (Ocean.fx / RiverWater.fx / Water.frag port) ----------------
+
+// Sample an atlas layer by an explicit layer index (the water flow/bump maps
+// are appended as the last two layers of the tile atlas).
+float3 water_tex(int layer, float2 uv) {
+    uint w = 0;
+    uint h = 0;
+    uint lc = 0;
+    atlas.GetDimensions(w, h, lc);
+    float l = (float) clamp(layer, 0, (int) lc - 1);
+    return atlas.Sample(atlas_smp, float3(uv, l)).rgb;
+}
+
+// Scrolling wave normal on the water plane: the retail bump map (atlas's last
+// layer), offset by the flow map (second-last layer) and combined with a
+// de-gridded procedural wave so the sun glint is irregular and always moving.
+float3 water_normal(float2 world_xy, float time) {
+    float2 q = world_xy * (WATER_SCALE * 6.0);
+    float a1 = q.x * 0.80 + q.y * 0.30 + time * 1.10;
+    float a2 = q.y * 0.95 - q.x * 0.45 - time * 1.30;
+    float a3 = (q.x + q.y) * 1.60 + time * 2.10;
+    float a4 = (q.x - q.y) * 2.30 - time * 1.70;
+    float dx = 0.224 * cos(a1) - 0.099 * cos(a2) + 0.256 * cos(a3) + 0.230 * cos(a4);
+    float dy = 0.084 * cos(a1) + 0.209 * cos(a2) + 0.256 * cos(a3) - 0.230 * cos(a4);
+    uint w = 0;
+    uint h = 0;
+    uint lc = 0;
+    atlas.GetDimensions(w, h, lc);
+    float3 flow = water_tex((int) lc - 2, q - float2(time * 0.010, time * 0.014)) * 2.0 - 1.0;
+    float3 bump = water_tex((int) lc - 1, q + flow.xy * 0.05 + float2(time * 0.006, time * 0.008)) * 2.0 - 1.0;
+    float sx = -dx * 0.30 + bump.x * 0.45;
+    float sy = -dy * 0.30 + bump.y * 0.45;
+    return normalize(float3(sx, sy, 1.0));
+}
+
+// Water.frag distortionPower * the flow texture: a small scrolling UV offset.
+float water_distortion(float2 world_xy, float time) {
+    float2 q = world_xy * (WATER_SCALE * 6.0);
+    return 0.05 * (sin(q.x * 0.9 + time * 0.7) + sin(q.y * 1.1 - time * 0.5));
+}
+
+// Water.frag GetCloudColor: no cloud texture is bound, so a slow low-frequency
+// scroll stands in.
+float3 water_cloud(float2 world_xy, float time) {
+    return float3(0.85 + 0.15 * sin((world_xy.x + world_xy.y) * 0.0007 - time * 0.05));
+}
+
+// Retail UnderwaterDeferred.fx: absorbs red and fogs with distance. Applied to
+// every output while the camera is below the water plane.
+float3 apply_underwater(float3 color, float dist, float cam_z, float water_z) {
+    if (cam_z >= water_z - 0.5) return color;
+    const float3 absorb = float3(0.35, 0.62, 0.75);
+    float fog = clamp(1.0 - exp(-dist * 0.00022), 0.0, 0.9);
+    return lerp(color * absorb, float3(0.02, 0.10, 0.16), fog);
+}
+
+// Water.frag: fresnel-mixed reflection (sky) and refraction (depth-graded
+// seabed), SAGE diffuse + specular lighting, cloud term, and a depth-based
+// transparency fade. `river` (>0.5) applies RiverTransparencyMultiplier.
+float3 water_shade(float3 hitpos, float3 dir, float dist) {
+    float time = misc.x;
+    float river = misc.y;
+    float seabed = world_height(hitpos.x, hitpos.y);
+    float depth = max(0.0, params.z - seabed);
+
+    float3 n = water_normal(hitpos.xy, time + water_distortion(hitpos.xy, time));
+    float3 sun_dir = normalize(sun.xyz);
+
+    // Schlick fresnel, water F0 = 0.02.
+    float cos_theta = clamp(dot(-dir, n), 0.0, 1.0);
+    float fresnel = 0.02 + 0.98 * pow(1.0 - cos_theta, 5.0);
+
+    // Reflection: the sky the surface mirrors. Refraction: the seabed, graded
+    // from shallow to deep and lit by the SAGE diffuse + specular model.
+    float3 reflection = sky_color(reflect(dir, n));
+    float3 shallow = float3(0.10, 0.34, 0.38);
+    float3 deep = float3(0.02, 0.12, 0.22);
+    float3 refraction = lerp(shallow, deep, clamp(depth / 40.0, 0.0, 1.0));
+
+    float ndotl = max(dot(n, sun_dir), 0.0);
+    float ambient = sun.w;
+    float3 diffuse = float3(ambient + (1.0 - ambient) * ndotl);
+    float3 half_v = normalize(sun_dir - dir);
+    float spec = pow(max(dot(n, half_v), 0.0), 90.0);
+
+    float3 color = lerp(refraction, reflection, clamp(fresnel, 0.0, 1.0)) * diffuse * water_cloud(hitpos.xy, time);
+    color += float3(1.0, 0.97, 0.9) * spec * 0.45;
+
+    // Depth-based transparency: shallow water shows the seabed, deep water goes
+    // opaque toward the deep colour.
+    float alpha = clamp(depth / WATER_TRANSPARENT_DEPTH, 0.0, 1.0) * WATER_MIN_OPACITY;
+    if (river > 0.5) alpha *= WATER_RIVER_MULTIPLIER;
+    color = lerp(refraction, color, clamp(alpha + 0.15, 0.0, 1.0));
+
+    // Distance haze toward the horizon, as the terrain.
+    float wfog = clamp(1.0 - exp(-dist * 0.00009), 0.0, 0.75);
+    return lerp(color, sky_color(float3(dir.x, dir.y, 0.0)), wfog);
+}
+
 float4 PSMain(VSOut input) : SV_Target {
     float4 p = cam;
     float pitch = clamp(params.x, 0.15, 1.45);
@@ -127,50 +236,75 @@ float4 PSMain(VSOut input) : SV_Target {
     float3 dir = normalize(fwd + right * ndc.x * th * aspect + up * ndc.y * th);
 
     if (dir.z >= -1e-4) {
-        return float4(sky_color(dir), 1.0);
+        return float4(apply_underwater(sky_color(dir), 0.0, cam_pos.z, params.z), 1.0);
     }
 
-    // March the heightfield. The step grows quickly: the map diagonal is only
-    // ~9000 world units, so marching past ~20000 adds cost without detail, and
-    // a 6% growth rate more than doubles the worst-case iteration count.
-    float t = CELL * 0.5;
-    float dt = CELL * 0.5;
+    // Clip the ray to the map's XY rectangle: the boundary is an exact plane,
+    // so the silhouette there stays razor-sharp instead of stair-stepping
+    // across it. Outside the map is sky.
+    float t_enter = 0.0;
+    float t_exit = 1.0e30;
+    bool inside = true;
+    if (abs(dir.x) < 1e-6) {
+        inside = (cam_pos.x >= 0.0 && cam_pos.x <= world_w);
+    } else {
+        float a = (0.0 - cam_pos.x) / dir.x;
+        float b = (world_w - cam_pos.x) / dir.x;
+        t_enter = max(t_enter, min(a, b));
+        t_exit = min(t_exit, max(a, b));
+    }
+    if (inside) {
+        if (abs(dir.y) < 1e-6) {
+            inside = (cam_pos.y >= 0.0 && cam_pos.y <= world_h);
+        } else {
+            float a = (0.0 - cam_pos.y) / dir.y;
+            float b = (world_h - cam_pos.y) / dir.y;
+            t_enter = max(t_enter, min(a, b));
+            t_exit = min(t_exit, max(a, b));
+        }
+    }
+    if (!inside || t_exit <= 0.0) {
+        return float4(apply_underwater(sky_color(dir), 0.0, cam_pos.z, params.z), 1.0);
+    }
+
+    // March the heightfield cell by cell: the step is never longer than the
+    // time to cross one cell (dominant horizontal axis), while a clearance term
+    // lets the ray skip the empty air above the surface. Resolving every cell is
+    // what keeps cliff and map-edge silhouettes from quantising into huge
+    // stair-steps that crawl as the camera pans.
+    float horiz = max(abs(dir.x), abs(dir.y));
+    float cell_step = min(CELL / max(horiz, 1e-4), CELL * 32.0);
+    float t = max(t_enter, CELL * 0.5);
     float prev = t;
     bool hit = false;
     float hit_t = 0.0;
-    for (int i = 0; i < 256 && t < 20000.0; ++i) {
+    for (int i = 0; i < 1024 && t <= t_exit; ++i) {
         float3 w = cam_pos + dir * t;
-        if (w.x < 0.0 || w.y < 0.0 || w.x >= world_w || w.y >= world_h) {
-            prev = t;
-            dt *= 1.10;
-            t += dt;
-            continue;
-        }
-        if (params.w > 0.5 && w.z <= params.z) {
-            hit = true;
-            hit_t = t;
-            break;
-        }
-        if (w.z <= world_height(w.x, w.y)) {
+        float h = world_height(w.x, w.y);
+        float surface = (params.w > 0.5) ? max(h, params.z) : h;
+        if (w.z <= surface) {
             hit = true;
             hit_t = t;
             break;
         }
+        float clearance = (w.z - surface) / max(-dir.z, 1e-4);
         prev = t;
-        dt *= 1.10;
-        t += dt;
+        t += clamp(clearance, cell_step, cell_step * 8.0);
     }
     if (!hit) {
-        return float4(sky_color(dir), 1.0);
+        return float4(apply_underwater(sky_color(dir), 0.0, cam_pos.z, params.z), 1.0);
     }
 
+    // Refine the first crossing; with a sub-cell bracket this converges to the
+    // exact surface point.
     float lo = prev;
     float hi = hit_t;
-    for (int i = 0; i < 6; ++i) {
+    for (int i = 0; i < 18; ++i) {
         float mid = 0.5 * (lo + hi);
         float3 w = cam_pos + dir * mid;
-        bool water = params.w > 0.5 && w.z <= params.z;
-        if (water || w.z <= world_height(w.x, w.y)) {
+        float h = world_height(w.x, w.y);
+        float surface = (params.w > 0.5) ? max(h, params.z) : h;
+        if (w.z <= surface) {
             hi = mid;
         } else {
             lo = mid;
@@ -182,21 +316,7 @@ float4 PSMain(VSOut input) : SV_Target {
     float ambient = sun.w;
 
     if (params.w > 0.5 && hitpos.z <= params.z + 0.01) {
-        // Water: animated normal from a procedural wave, sky reflection + fresnel.
-        float time = misc.x;
-        float2 q = hitpos.xy * 0.015;
-        float nx = sin(q.x * 1.3 + time * 1.7) + 0.5 * sin(q.x * 3.1 - time * 2.3);
-        float ny = sin(q.y * 1.1 - time * 1.3) + 0.5 * sin(q.y * 2.7 + time * 1.9);
-        float3 n = normalize(float3(nx * 0.06, ny * 0.06, 1.0));
-        float fres = pow(1.0 - clamp(-dir.z, 0.0, 1.0), 3.0);
-        float3 deep = float3(0.03, 0.16, 0.28);
-        float3 refl = sky_color(reflect(dir, n));
-        float lam = max(0.0, dot(n, sun_dir));
-        float3 water = lerp(deep, refl, clamp(0.25 + 0.55 * fres, 0.0, 0.9));
-        water += float3(1.0, 0.98, 0.9) * pow(lam, 64.0) * 0.6; // sun glint
-        float wfog = clamp(1.0 - exp(-hi * 0.00009), 0.0, 0.75);
-        water = lerp(water, sky_color(float3(dir.x, dir.y, 0.0)), wfog);
-        return float4(water, 1.0);
+        return float4(apply_underwater(water_shade(hitpos, dir, hi), hi, cam_pos.z, params.z), 1.0);
     }
 
     // Terrain: read the per-cell blend record, sample the base/blend/three-way
@@ -234,5 +354,5 @@ float4 PSMain(VSOut input) : SV_Target {
     // Distance haze toward the horizon so the map edge blends into the sky.
     float fog = clamp(1.0 - exp(-hi * 0.00009), 0.0, 0.75);
     lit = lerp(lit, sky_color(float3(dir.x, dir.y, 0.0)), fog);
-    return float4(lit, 1.0);
+    return float4(apply_underwater(lit, hi, cam_pos.z, params.z), 1.0);
 }

shaders/terrain.frag

@@ -8,6 +8,10 @@
 // The material is sampled **continuously** (`uv = cell / (2 * cellSize)`), as the
 // retail `Terrain.fx` / OpenSAGE `Terrain.frag` do, so it never restarts at a
 // cell edge; material boundaries cross-fade with the SAGE blend ramp.
+//
+// The water plane is shaded with a port of the SAGE water effect
+// (`Ocean.fx` / OpenSAGE `Water.frag`); the camera-below-water tint stands in
+// for `UnderwaterDeferred.fx`. See docs/REVERSE_ENGINEERING.md.
 layout(binding = 0) uniform sampler2D heightmap;
 layout(binding = 1) uniform sampler2D celldata;
 layout(binding = 2) uniform sampler2DArray atlas;
@@ -17,7 +21,7 @@ layout(push_constant) uniform Push {
     vec4 params;  // x=pitch, y=fov, z=water_z, w=has_water
     vec4 sun;     // xyz=sun dir, w=ambient
     vec4 mapinfo; // x=W, y=H, z=unused, w=z_scale
-    vec4 misc;    // x=time, y=unused, z=cells per texture repeat, w=aspect
+    vec4 misc;    // x=time, y=water kind (0=ocean,1=river), z=cells per repeat, w=aspect
 } pc;
 
 layout(location = 0) in vec2 in_uv;
@@ -30,6 +34,12 @@ const float CELL = 10.0; // must match ra3::terrain::cell_size
 const float NEAR = 10.0;
 const float FAR = 60000.0;
 
+// SAGE water model constants (see docs/REVERSE_ENGINEERING.md).
+const float WATER_SCALE = 1.0 / 320.0;      // Water.frag: worldPos.xy / 320
+const float WATER_TRANSPARENT_DEPTH = 10.0; // WaterTransparency.TransparentWaterDepth
+const float WATER_MIN_OPACITY = 0.70;       // WaterTransparency.TransparentWaterMinOpacity
+const float WATER_RIVER_MULTIPLIER = 1.0;   // WaterTransparency.RiverTransparencyMultiplier
+
 float height_at(ivec2 c) {
     c = clamp(c, ivec2(0), ivec2(pc.mapinfo.xy) - 1);
     return texelFetch(heightmap, c, 0).r * 65535.0 * pc.mapinfo.w;
@@ -92,6 +102,99 @@ vec3 sample_layer(uint layer, float wx, float wy) {
     return texture(atlas, vec3(vec2(wx, wy) / span, l)).rgb;
 }
 
+// ---- SAGE water (Ocean.fx / RiverWater.fx / Water.frag port) ----------------
+
+// Sample an atlas layer by an explicit float layer index (the water flow/bump
+// maps are appended as the last two layers of the tile atlas).
+vec3 water_tex(int layer, vec2 uv) {
+    int lc = textureSize(atlas, 0).z;
+    float l = float(clamp(layer, 0, max(lc - 1, 0)));
+    return texture(atlas, vec3(uv, l)).rgb;
+}
+
+// Scrolling wave normal on the water plane: the retail bump map (atlas's last
+// layer), offset by the flow map (second-last layer) and combined with a
+// de-gridded procedural wave so the sun glint is irregular and always moving.
+vec3 water_normal(vec2 world_xy, float time) {
+    vec2 q = world_xy * (WATER_SCALE * 6.0);
+    float a1 = q.x * 0.80 + q.y * 0.30 + time * 1.10;
+    float a2 = q.y * 0.95 - q.x * 0.45 - time * 1.30;
+    float a3 = (q.x + q.y) * 1.60 + time * 2.10;
+    float a4 = (q.x - q.y) * 2.30 - time * 1.70;
+    float dx = 0.224 * cos(a1) - 0.099 * cos(a2) + 0.256 * cos(a3) + 0.230 * cos(a4);
+    float dy = 0.084 * cos(a1) + 0.209 * cos(a2) + 0.256 * cos(a3) - 0.230 * cos(a4);
+    int lc = textureSize(atlas, 0).z;
+    vec3 flow = water_tex(lc - 2, q - vec2(time * 0.010, time * 0.014)) * 2.0 - 1.0;
+    vec3 bump = water_tex(lc - 1, q + flow.xy * 0.05 + vec2(time * 0.006, time * 0.008)) * 2.0 - 1.0;
+    float sx = -dx * 0.30 + bump.x * 0.45;
+    float sy = -dy * 0.30 + bump.y * 0.45;
+    return normalize(vec3(sx, sy, 1.0));
+}
+
+// Water.frag distortionPower * the flow texture: a small scrolling UV offset.
+float water_distortion(vec2 world_xy, float time) {
+    vec2 q = world_xy * (WATER_SCALE * 6.0);
+    return 0.05 * (sin(q.x * 0.9 + time * 0.7) + sin(q.y * 1.1 - time * 0.5));
+}
+
+// Water.frag GetCloudColor: no cloud texture is bound, so a slow low-frequency
+// scroll stands in.
+vec3 water_cloud(vec2 world_xy, float time) {
+    return vec3(0.85 + 0.15 * sin((world_xy.x + world_xy.y) * 0.0007 - time * 0.05));
+}
+
+// Retail UnderwaterDeferred.fx: absorbs red and fogs with distance. Applied to
+// every output while the camera is below the water plane.
+vec3 apply_underwater(vec3 color, float dist, float cam_z, float water_z) {
+    if (cam_z >= water_z - 0.5) return color;
+    const vec3 absorb = vec3(0.35, 0.62, 0.75);
+    float fog = clamp(1.0 - exp(-dist * 0.00022), 0.0, 0.9);
+    return mix(color * absorb, vec3(0.02, 0.10, 0.16), fog);
+}
+
+// Water.frag: fresnel-mixed reflection (sky) and refraction (depth-graded
+// seabed), SAGE diffuse + specular lighting, cloud term, and a depth-based
+// transparency fade. `river` (>0.5) applies RiverTransparencyMultiplier.
+vec3 water_shade(vec3 hitpos, vec3 dir, float dist) {
+    float time = pc.misc.x;
+    float river = pc.misc.y;
+    float seabed = world_height(hitpos.x, hitpos.y);
+    float depth = max(0.0, pc.params.z - seabed);
+
+    vec3 n = water_normal(hitpos.xy, time + water_distortion(hitpos.xy, time));
+    vec3 sun = normalize(pc.sun.xyz);
+
+    // Schlick fresnel, water F0 = 0.02.
+    float cos_theta = clamp(dot(-dir, n), 0.0, 1.0);
+    float fresnel = 0.02 + 0.98 * pow(1.0 - cos_theta, 5.0);
+
+    // Reflection: the sky the surface mirrors. Refraction: the seabed, graded
+    // from shallow to deep and lit by the SAGE diffuse + specular model.
+    vec3 reflection = sky_color(reflect(dir, n));
+    vec3 shallow = vec3(0.10, 0.34, 0.38);
+    vec3 deep = vec3(0.02, 0.12, 0.22);
+    vec3 refraction = mix(shallow, deep, clamp(depth / 40.0, 0.0, 1.0));
+
+    float ndotl = max(dot(n, sun), 0.0);
+    float ambient = pc.sun.w;
+    vec3 diffuse = vec3(ambient + (1.0 - ambient) * ndotl);
+    vec3 half_v = normalize(sun - dir);
+    float spec = pow(max(dot(n, half_v), 0.0), 90.0);
+
+    vec3 color = mix(refraction, reflection, clamp(fresnel, 0.0, 1.0)) * diffuse * water_cloud(hitpos.xy, time);
+    color += vec3(1.0, 0.97, 0.9) * spec * 0.45;
+
+    // Depth-based transparency: shallow water shows the seabed, deep water goes
+    // opaque toward the deep colour.
+    float alpha = clamp(depth / WATER_TRANSPARENT_DEPTH, 0.0, 1.0) * WATER_MIN_OPACITY;
+    if (river > 0.5) alpha *= WATER_RIVER_MULTIPLIER;
+    color = mix(refraction, color, clamp(alpha + 0.15, 0.0, 1.0));
+
+    // Distance haze toward the horizon, as the terrain.
+    float wfog = clamp(1.0 - exp(-dist * 0.00009), 0.0, 0.75);
+    return mix(color, sky_color(vec3(dir.x, dir.y, 0.0)), wfog);
+}
+
 void main() {
     vec4 p = pc.cam;
     float pitch = clamp(pc.params.x, 0.15, 1.45);
@@ -118,35 +221,71 @@ void main() {
 
     if (dir.z >= -1e-4) {
         gl_FragDepth = 1.0;
-        out_color = vec4(sky_color(dir), 1.0);
+        out_color = vec4(apply_underwater(sky_color(dir), 0.0, cam.z, pc.params.z), 1.0);
         return;
     }
 
-    // March the heightfield. The step grows quickly: the map diagonal is only
-    // ~9000 world units, so marching past ~20000 adds cost without detail, and
-    // a 6% growth rate more than doubles the worst-case iteration count.
-    float t = CELL * 0.5;
-    float dt = CELL * 0.5;
+    // Clip the ray to the map's XY rectangle: the boundary is an exact plane,
+    // so the silhouette there stays razor-sharp instead of stair-stepping
+    // across it. Outside the map is sky.
+    float t_enter = 0.0;
+    float t_exit = 1.0e30;
+    bool inside = true;
+    if (abs(dir.x) < 1e-6) {
+        inside = (cam.x >= 0.0 && cam.x <= world_w);
+    } else {
+        float a = (0.0 - cam.x) / dir.x;
+        float b = (world_w - cam.x) / dir.x;
+        t_enter = max(t_enter, min(a, b));
+        t_exit = min(t_exit, max(a, b));
+    }
+    if (inside) {
+        if (abs(dir.y) < 1e-6) {
+            inside = (cam.y >= 0.0 && cam.y <= world_h);
+        } else {
+            float a = (0.0 - cam.y) / dir.y;
+            float b = (world_h - cam.y) / dir.y;
+            t_enter = max(t_enter, min(a, b));
+            t_exit = min(t_exit, max(a, b));
+        }
+    }
+    if (!inside || t_exit <= 0.0) {
+        gl_FragDepth = 1.0;
+        out_color = vec4(apply_underwater(sky_color(dir), 0.0, cam.z, pc.params.z), 1.0);
+        return;
+    }
+
+    // March the heightfield cell by cell: the step is never longer than the
+    // time to cross one cell (dominant horizontal axis), while a clearance term
+    // lets the ray skip the empty air above the surface. Resolving every cell is
+    // what keeps cliff and map-edge silhouettes from quantising into huge
+    // stair-steps that crawl as the camera pans.
+    float horiz = max(abs(dir.x), abs(dir.y));
+    float cell_step = min(CELL / max(horiz, 1e-4), CELL * 32.0);
+    float t = max(t_enter, CELL * 0.5);
     float prev = t;
     bool hit = false;
     float hit_t = 0.0;
-    for (int i = 0; i < 256 && t < 20000.0; ++i) {
+    for (int i = 0; i < 1024 && t <= t_exit; ++i) {
         vec3 w = cam + dir * t;
-        if (w.x < 0.0 || w.y < 0.0 || w.x >= world_w || w.y >= world_h) {
-            prev = t; dt *= 1.10; t += dt; continue;
-        }
-        if (pc.params.w > 0.5 && w.z <= pc.params.z) { hit = true; hit_t = t; break; }
-        if (w.z <= world_height(w.x, w.y)) { hit = true; hit_t = t; break; }
-        prev = t; dt *= 1.10; t += dt;
+        float h = world_height(w.x, w.y);
+        float surface = (pc.params.w > 0.5) ? max(h, pc.params.z) : h;
+        if (w.z <= surface) { hit = true; hit_t = t; break; }
+        float clearance = (w.z - surface) / max(-dir.z, 1e-4);
+        prev = t;
+        t += clamp(clearance, cell_step, cell_step * 8.0);
     }
-    if (!hit) { gl_FragDepth = 1.0; out_color = vec4(sky_color(dir), 1.0); return; }
+    if (!hit) { gl_FragDepth = 1.0; out_color = vec4(apply_underwater(sky_color(dir), 0.0, cam.z, pc.params.z), 1.0); return; }
 
+    // Refine the first crossing; with a sub-cell bracket this converges to the
+    // exact surface point.
     float lo = prev, hi = hit_t;
-    for (int i = 0; i < 6; ++i) {
+    for (int i = 0; i < 18; ++i) {
         float mid = 0.5 * (lo + hi);
         vec3 w = cam + dir * mid;
-        bool water = pc.params.w > 0.5 && w.z <= pc.params.z;
-        if (water || w.z <= world_height(w.x, w.y)) hi = mid; else lo = mid;
+        float h = world_height(w.x, w.y);
+        float surface = (pc.params.w > 0.5) ? max(h, pc.params.z) : h;
+        if (w.z <= surface) hi = mid; else lo = mid;
     }
     vec3 hitpos = cam + dir * hi;
 
@@ -158,21 +297,7 @@ void main() {
     float ambient = pc.sun.w;
 
     if (pc.params.w > 0.5 && hitpos.z <= pc.params.z + 0.01) {
-        // Water: animated normal from a procedural wave, sky reflection + fresnel.
-        float time = pc.misc.x;
-        vec2 q = hitpos.xy * 0.015;
-        float nx = sin(q.x * 1.3 + time * 1.7) + 0.5 * sin(q.x * 3.1 - time * 2.3);
-        float ny = sin(q.y * 1.1 - time * 1.3) + 0.5 * sin(q.y * 2.7 + time * 1.9);
-        vec3 n = normalize(vec3(nx * 0.06, ny * 0.06, 1.0));
-        float fres = pow(1.0 - clamp(-dir.z, 0.0, 1.0), 3.0);
-        vec3 deep = vec3(0.03, 0.16, 0.28);
-        vec3 refl = sky_color(reflect(dir, n));
-        float lam = max(0.0, dot(n, sun));
-        vec3 water = mix(deep, refl, clamp(0.25 + 0.55 * fres, 0.0, 0.9));
-        water += vec3(1.0, 0.98, 0.9) * pow(lam, 64.0) * 0.6; // sun glint
-        float wfog = clamp(1.0 - exp(-hi * 0.00009), 0.0, 0.75);
-        water = mix(water, sky_color(vec3(dir.x, dir.y, 0.0)), wfog);
-        out_color = vec4(water, 1.0);
+        out_color = vec4(apply_underwater(water_shade(hitpos, dir, hi), hi, cam.z, pc.params.z), 1.0);
         return;
     }
 
@@ -211,5 +336,5 @@ void main() {
     // Distance haze toward the horizon so the map edge blends into the sky.
     float fog = clamp(1.0 - exp(-hi * 0.00009), 0.0, 0.75);
     lit = mix(lit, sky_color(vec3(dir.x, dir.y, 0.0)), fog);
-    out_color = vec4(lit, 1.0);
+    out_color = vec4(apply_underwater(lit, hi, cam.z, pc.params.z), 1.0);
 }

shaders/webgl_terrain_frag.glsl

@@ -24,6 +24,12 @@ out vec4 frag_color;
 
 const float CELL = 10.0; // must match ra3::terrain::cell_size
 
+// SAGE water model constants (see docs/REVERSE_ENGINEERING.md).
+const float WATER_SCALE = 1.0 / 320.0;
+const float WATER_TRANSPARENT_DEPTH = 10.0;
+const float WATER_MIN_OPACITY = 0.70;
+const float WATER_RIVER_MULTIPLIER = 1.0;
+
 float height_at(ivec2 c) {
     c = clamp(c, ivec2(0), ivec2(u_mapinfo.xy) - 1);
     return texelFetch(u_heightmap, c, 0).r * 65535.0 * u_mapinfo.w;
@@ -82,6 +88,91 @@ vec3 sample_layer(uint layer, float wx, float wy) {
     return texture(u_atlas, vec3(vec2(wx, wy) / span, l)).bgr;
 }
 
+// ---- SAGE water (Ocean.fx / RiverWater.fx / Water.frag port) ----------------
+
+// Sample an atlas layer by an explicit layer index (the water flow/bump maps
+// are appended as the last two layers of the tile atlas). The atlas is
+// 0xAARRGGBB, so `.bgr` restores RGB (as `sample_layer`).
+vec3 water_tex(int layer, vec2 uv) {
+    int lc = textureSize(u_atlas, 0).z;
+    float l = float(clamp(layer, 0, max(lc - 1, 0)));
+    return texture(u_atlas, vec3(uv, l)).bgr;
+}
+
+// Scrolling wave normal on the water plane: the retail bump map (atlas's last
+// layer), offset by the flow map (second-last layer) and combined with a
+// de-gridded procedural wave so the sun glint is irregular and always moving.
+vec3 water_normal(vec2 world_xy, float time) {
+    vec2 q = world_xy * (WATER_SCALE * 6.0);
+    float a1 = q.x * 0.80 + q.y * 0.30 + time * 1.10;
+    float a2 = q.y * 0.95 - q.x * 0.45 - time * 1.30;
+    float a3 = (q.x + q.y) * 1.60 + time * 2.10;
+    float a4 = (q.x - q.y) * 2.30 - time * 1.70;
+    float dx = 0.224 * cos(a1) - 0.099 * cos(a2) + 0.256 * cos(a3) + 0.230 * cos(a4);
+    float dy = 0.084 * cos(a1) + 0.209 * cos(a2) + 0.256 * cos(a3) - 0.230 * cos(a4);
+    int lc = textureSize(u_atlas, 0).z;
+    vec3 flow = water_tex(lc - 2, q - vec2(time * 0.010, time * 0.014)) * 2.0 - 1.0;
+    vec3 bump = water_tex(lc - 1, q + flow.xy * 0.05 + vec2(time * 0.006, time * 0.008)) * 2.0 - 1.0;
+    float sx = -dx * 0.30 + bump.x * 0.45;
+    float sy = -dy * 0.30 + bump.y * 0.45;
+    return normalize(vec3(sx, sy, 1.0));
+}
+
+// Water.frag distortionPower * the flow texture: a small scrolling UV offset.
+float water_distortion(vec2 world_xy, float time) {
+    vec2 q = world_xy * (WATER_SCALE * 6.0);
+    return 0.05 * (sin(q.x * 0.9 + time * 0.7) + sin(q.y * 1.1 - time * 0.5));
+}
+
+// Water.frag GetCloudColor: no cloud texture is bound, so a slow scroll stands in.
+vec3 water_cloud(vec2 world_xy, float time) {
+    return vec3(0.85 + 0.15 * sin((world_xy.x + world_xy.y) * 0.0007 - time * 0.05));
+}
+
+// Retail UnderwaterDeferred.fx: absorbs red and fogs with distance.
+vec3 apply_underwater(vec3 color, float dist, float cam_z, float water_z) {
+    if (cam_z >= water_z - 0.5) return color;
+    const vec3 absorb = vec3(0.35, 0.62, 0.75);
+    float fog = clamp(1.0 - exp(-dist * 0.00022), 0.0, 0.9);
+    return mix(color * absorb, vec3(0.02, 0.10, 0.16), fog);
+}
+
+// Water.frag: fresnel-mixed sky reflection and depth-graded seabed refraction,
+// SAGE diffuse + specular lighting, cloud term, depth-based transparency fade.
+vec3 water_shade(vec3 hitpos, vec3 dir, float dist) {
+    float time = u_misc.x;
+    float river = u_misc.y;
+    float seabed = world_height(hitpos.x, hitpos.y);
+    float depth = max(0.0, u_params.z - seabed);
+
+    vec3 n = water_normal(hitpos.xy, time + water_distortion(hitpos.xy, time));
+    vec3 sun_dir = normalize(u_sun.xyz);
+
+    float cos_theta = clamp(dot(-dir, n), 0.0, 1.0);
+    float fresnel = 0.02 + 0.98 * pow(1.0 - cos_theta, 5.0);
+
+    vec3 reflection = sky_color(reflect(dir, n));
+    vec3 shallow = vec3(0.10, 0.34, 0.38);
+    vec3 deep = vec3(0.02, 0.12, 0.22);
+    vec3 refraction = mix(shallow, deep, clamp(depth / 40.0, 0.0, 1.0));
+
+    float ndotl = max(dot(n, sun_dir), 0.0);
+    float ambient = u_sun.w;
+    vec3 diffuse = vec3(ambient + (1.0 - ambient) * ndotl);
+    vec3 half_v = normalize(sun_dir - dir);
+    float spec = pow(max(dot(n, half_v), 0.0), 90.0);
+
+    vec3 color = mix(refraction, reflection, clamp(fresnel, 0.0, 1.0)) * diffuse * water_cloud(hitpos.xy, time);
+    color += vec3(1.0, 0.97, 0.9) * spec * 0.45;
+
+    float alpha = clamp(depth / WATER_TRANSPARENT_DEPTH, 0.0, 1.0) * WATER_MIN_OPACITY;
+    if (river > 0.5) alpha *= WATER_RIVER_MULTIPLIER;
+    color = mix(refraction, color, clamp(alpha + 0.15, 0.0, 1.0));
+
+    float wfog = clamp(1.0 - exp(-dist * 0.00009), 0.0, 0.75);
+    return mix(color, sky_color(vec3(dir.x, dir.y, 0.0)), wfog);
+}
+
 void main() {
     vec4 p = u_cam;
     float pitch = clamp(u_params.x, 0.15, 1.45);
@@ -105,52 +196,78 @@ void main() {
     vec3 dir = normalize(fwd + right * ndc.x * th * aspect + up * ndc.y * th);
 
     if (dir.z >= -1e-4) {
-        frag_color = vec4(sky_color(dir), 1.0);
+        frag_color = vec4(apply_underwater(sky_color(dir), 0.0, cam.z, u_params.z), 1.0);
         return;
     }
 
-    // March the heightfield. The step grows quickly: the map diagonal is only
-    // ~9000 world units, so marching past ~20000 adds cost without detail, and
-    // a 6% growth rate more than doubles the worst-case iteration count.
-    float t = CELL * 0.5;
-    float dt = CELL * 0.5;
+    // Clip the ray to the map's XY rectangle: the boundary is an exact plane,
+    // so the silhouette there stays razor-sharp instead of stair-stepping
+    // across it. Outside the map is sky.
+    float t_enter = 0.0;
+    float t_exit = 1.0e30;
+    bool inside = true;
+    if (abs(dir.x) < 1e-6) {
+        inside = (cam.x >= 0.0 && cam.x <= world_w);
+    } else {
+        float a = (0.0 - cam.x) / dir.x;
+        float b = (world_w - cam.x) / dir.x;
+        t_enter = max(t_enter, min(a, b));
+        t_exit = min(t_exit, max(a, b));
+    }
+    if (inside) {
+        if (abs(dir.y) < 1e-6) {
+            inside = (cam.y >= 0.0 && cam.y <= world_h);
+        } else {
+            float a = (0.0 - cam.y) / dir.y;
+            float b = (world_h - cam.y) / dir.y;
+            t_enter = max(t_enter, min(a, b));
+            t_exit = min(t_exit, max(a, b));
+        }
+    }
+    if (!inside || t_exit <= 0.0) {
+        frag_color = vec4(apply_underwater(sky_color(dir), 0.0, cam.z, u_params.z), 1.0);
+        return;
+    }
+
+    // March the heightfield cell by cell: the step is never longer than the
+    // time to cross one cell (dominant horizontal axis), while a clearance term
+    // lets the ray skip the empty air above the surface. Resolving every cell is
+    // what keeps cliff and map-edge silhouettes from quantising into huge
+    // stair-steps that crawl as the camera pans.
+    float horiz = max(abs(dir.x), abs(dir.y));
+    float cell_step = min(CELL / max(horiz, 1e-4), CELL * 32.0);
+    float t = max(t_enter, CELL * 0.5);
     float prev = t;
     bool hit = false;
     float hit_t = 0.0;
-    for (int i = 0; i < 256 && t < 20000.0; ++i) {
+    for (int i = 0; i < 1024 && t <= t_exit; ++i) {
         vec3 w = cam + dir * t;
-        if (w.x < 0.0 || w.y < 0.0 || w.x >= world_w || w.y >= world_h) {
-            prev = t;
-            dt *= 1.10;
-            t += dt;
-            continue;
-        }
-        if (u_params.w > 0.5 && w.z <= u_params.z) {
-            hit = true;
-            hit_t = t;
-            break;
-        }
-        if (w.z <= world_height(w.x, w.y)) {
+        float h = world_height(w.x, w.y);
+        float surface = (u_params.w > 0.5) ? max(h, u_params.z) : h;
+        if (w.z <= surface) {
             hit = true;
             hit_t = t;
             break;
         }
+        float clearance = (w.z - surface) / max(-dir.z, 1e-4);
         prev = t;
-        dt *= 1.10;
-        t += dt;
+        t += clamp(clearance, cell_step, cell_step * 8.0);
     }
     if (!hit) {
-        frag_color = vec4(sky_color(dir), 1.0);
+        frag_color = vec4(apply_underwater(sky_color(dir), 0.0, cam.z, u_params.z), 1.0);
         return;
     }
 
+    // Refine the first crossing; with a sub-cell bracket this converges to the
+    // exact surface point.
     float lo = prev;
     float hi = hit_t;
-    for (int i = 0; i < 6; ++i) {
+    for (int i = 0; i < 18; ++i) {
         float mid = 0.5 * (lo + hi);
         vec3 w = cam + dir * mid;
-        bool water = u_params.w > 0.5 && w.z <= u_params.z;
-        if (water || w.z <= world_height(w.x, w.y)) {
+        float h = world_height(w.x, w.y);
+        float surface = (u_params.w > 0.5) ? max(h, u_params.z) : h;
+        if (w.z <= surface) {
             hi = mid;
         } else {
             lo = mid;
@@ -162,20 +279,7 @@ void main() {
     float ambient = u_sun.w;
 
     if (u_params.w > 0.5 && hitpos.z <= u_params.z + 0.01) {
-        float time = u_misc.x;
-        vec2 q = hitpos.xy * 0.015;
-        float nx = sin(q.x * 1.3 + time * 1.7) + 0.5 * sin(q.x * 3.1 - time * 2.3);
-        float ny = sin(q.y * 1.1 - time * 1.3) + 0.5 * sin(q.y * 2.7 + time * 1.9);
-        vec3 n = normalize(vec3(nx * 0.06, ny * 0.06, 1.0));
-        float fres = pow(1.0 - clamp(-dir.z, 0.0, 1.0), 3.0);
-        vec3 deep = vec3(0.03, 0.16, 0.28);
-        vec3 refl = sky_color(reflect(dir, n));
-        float lam = max(0.0, dot(n, sun));
-        vec3 water = mix(deep, refl, clamp(0.25 + 0.55 * fres, 0.0, 0.9));
-        water += vec3(1.0, 0.98, 0.9) * pow(lam, 64.0) * 0.6;
-        float wfog = clamp(1.0 - exp(-hi * 0.00009), 0.0, 0.75);
-        water = mix(water, sky_color(vec3(dir.x, dir.y, 0.0)), wfog);
-        frag_color = vec4(water, 1.0);
+        frag_color = vec4(apply_underwater(water_shade(hitpos, dir, hi), hi, cam.z, u_params.z), 1.0);
         return;
     }
 
@@ -210,5 +314,5 @@ void main() {
     vec3 lit = albedo * (ambient + (1.0 - ambient) * lambert);
     float fog = clamp(1.0 - exp(-hi * 0.00009), 0.0, 0.75);
     lit = mix(lit, sky_color(vec3(dir.x, dir.y, 0.0)), fog);
-    frag_color = vec4(lit, 1.0);
+    frag_color = vec4(apply_underwater(lit, hi, cam.z, u_params.z), 1.0);
 }

shaders/webgpu_terrain.wgsl

@@ -17,6 +17,12 @@ struct TerrainUniforms {
 
 const CELL: f32 = 10.0; // must match ra3::terrain::cell_size
 
+// SAGE water model constants (see docs/REVERSE_ENGINEERING.md).
+const WATER_SCALE: f32 = 1.0 / 320.0;
+const WATER_TRANSPARENT_DEPTH: f32 = 10.0;
+const WATER_MIN_OPACITY: f32 = 0.70;
+const WATER_RIVER_MULTIPLIER: f32 = 1.0;
+
 fn cam_uniform() -> vec4<f32> { return u.data[0]; }    // x=target_x, y=target_y, z=yaw, w=height
 fn params_uniform() -> vec4<f32> { return u.data[1]; } // x=pitch, y=fov, z=water_z, w=has_water
 fn sun_uniform() -> vec4<f32> { return u.data[2]; }    // xyz=sun dir, w=ambient
@@ -100,6 +106,92 @@ fn sample_layer(layer: u32, wx: f32, wy: f32) -> vec3<f32> {
     return vec3<f32>(c.b, c.g, c.r);
 }
 
+// ---- SAGE water (Ocean.fx / RiverWater.fx / Water.frag port) ----------------
+
+// Sample an atlas layer by an explicit layer index (the water flow/bump maps
+// are appended as the last two layers of the tile atlas). The atlas is
+// 0xAARRGGBB, so the b/g/r swap restores RGB (as `sample_layer`).
+fn water_tex(layer: i32, uv: vec2<f32>) -> vec3<f32> {
+    let lc = i32(textureNumLayers(u_atlas));
+    let l = clamp(layer, 0, max(lc - 1, 0));
+    let c = textureSampleLevel(u_atlas, u_atlas_samp, uv, l, 0.0);
+    return vec3<f32>(c.b, c.g, c.r);
+}
+
+// Scrolling wave normal on the water plane: the retail bump map (atlas's last
+// layer), offset by the flow map (second-last layer) and combined with a
+// de-gridded procedural wave so the sun glint is irregular and always moving.
+fn water_normal(world_xy: vec2<f32>, time: f32) -> vec3<f32> {
+    let q = world_xy * (WATER_SCALE * 6.0);
+    let a1 = q.x * 0.80 + q.y * 0.30 + time * 1.10;
+    let a2 = q.y * 0.95 - q.x * 0.45 - time * 1.30;
+    let a3 = (q.x + q.y) * 1.60 + time * 2.10;
+    let a4 = (q.x - q.y) * 2.30 - time * 1.70;
+    let dx = 0.224 * cos(a1) - 0.099 * cos(a2) + 0.256 * cos(a3) + 0.230 * cos(a4);
+    let dy = 0.084 * cos(a1) + 0.209 * cos(a2) + 0.256 * cos(a3) - 0.230 * cos(a4);
+    let lc = i32(textureNumLayers(u_atlas));
+    let flow = water_tex(lc - 2, q - vec2<f32>(time * 0.010, time * 0.014)) * 2.0 - 1.0;
+    let bump = water_tex(lc - 1, q + flow.xy * 0.05 + vec2<f32>(time * 0.006, time * 0.008)) * 2.0 - 1.0;
+    let sx = -dx * 0.30 + bump.x * 0.45;
+    let sy = -dy * 0.30 + bump.y * 0.45;
+    return normalize(vec3<f32>(sx, sy, 1.0));
+}
+
+// Water.frag distortionPower * the flow texture: a small scrolling UV offset.
+fn water_distortion(world_xy: vec2<f32>, time: f32) -> f32 {
+    let q = world_xy * (WATER_SCALE * 6.0);
+    return 0.05 * (sin(q.x * 0.9 + time * 0.7) + sin(q.y * 1.1 - time * 0.5));
+}
+
+// Water.frag GetCloudColor: no cloud texture is bound, so a slow scroll stands in.
+fn water_cloud(world_xy: vec2<f32>, time: f32) -> vec3<f32> {
+    return vec3<f32>(0.85 + 0.15 * sin((world_xy.x + world_xy.y) * 0.0007 - time * 0.05));
+}
+
+// Retail UnderwaterDeferred.fx: absorbs red and fogs with distance.
+fn apply_underwater(color: vec3<f32>, distance: f32, cam_z: f32, water_z: f32) -> vec3<f32> {
+    if (cam_z >= water_z - 0.5) { return color; }
+    let absorb = vec3<f32>(0.35, 0.62, 0.75);
+    let fog = clamp(1.0 - exp(-distance * 0.00022), 0.0, 0.9);
+    return mix(color * absorb, vec3<f32>(0.02, 0.10, 0.16), fog);
+}
+
+// Water.frag: fresnel-mixed sky reflection and depth-graded seabed refraction,
+// SAGE diffuse + specular lighting, cloud term, depth-based transparency fade.
+fn water_shade(hitpos: vec3<f32>, dir: vec3<f32>, distance: f32) -> vec3<f32> {
+    let time = misc_uniform().x;
+    let river = misc_uniform().y;
+    let seabed = world_height(hitpos.x, hitpos.y);
+    let depth = max(0.0, params_uniform().z - seabed);
+
+    let n = water_normal(hitpos.xy, time + water_distortion(hitpos.xy, time));
+    let sun_dir = normalize(sun_uniform().xyz);
+
+    let cos_theta = clamp(dot(-dir, n), 0.0, 1.0);
+    let fresnel = 0.02 + 0.98 * pow(1.0 - cos_theta, 5.0);
+
+    let reflection = sky_color(reflect(dir, n));
+    let shallow = vec3<f32>(0.10, 0.34, 0.38);
+    let deep = vec3<f32>(0.02, 0.12, 0.22);
+    let refraction = mix(shallow, deep, clamp(depth / 40.0, 0.0, 1.0));
+
+    let ndotl = max(dot(n, sun_dir), 0.0);
+    let ambient = sun_uniform().w;
+    let diffuse = vec3<f32>(ambient + (1.0 - ambient) * ndotl);
+    let half_v = normalize(sun_dir - dir);
+    let spec = pow(max(dot(n, half_v), 0.0), 90.0);
+
+    var color = mix(refraction, reflection, clamp(fresnel, 0.0, 1.0)) * diffuse * water_cloud(hitpos.xy, time);
+    color += vec3<f32>(1.0, 0.97, 0.9) * spec * 0.45;
+
+    var alpha = clamp(depth / WATER_TRANSPARENT_DEPTH, 0.0, 1.0) * WATER_MIN_OPACITY;
+    if (river > 0.5) { alpha *= WATER_RIVER_MULTIPLIER; }
+    color = mix(refraction, color, clamp(alpha + 0.15, 0.0, 1.0));
+
+    let wfog = clamp(1.0 - exp(-distance * 0.00009), 0.0, 0.75);
+    return mix(color, sky_color(vec3<f32>(dir.x, dir.y, 0.0)), wfog);
+}
+
 @fragment
 fn fs_main(in: TerrainOut) -> @location(0) vec4<f32> {
     let p = cam_uniform();
@@ -124,49 +216,75 @@ fn fs_main(in: TerrainOut) -> @location(0) vec4<f32> {
     let dir = normalize(fwd + right * ndc.x * th * aspect + up * ndc.y * th);
 
     if (dir.z >= -1e-4) {
-        return vec4<f32>(sky_color(dir), 1.0);
+        return vec4<f32>(apply_underwater(sky_color(dir), 0.0, cam.z, params_uniform().z), 1.0);
     }
 
-    // March the heightfield. The step grows quickly: the map diagonal is only
-    // ~9000 world units, so marching past ~20000 adds cost without detail.
-    var t = CELL * 0.5;
-    var dt = CELL * 0.5;
+    // Clip the ray to the map's XY rectangle: the boundary is an exact plane,
+    // so the silhouette there stays razor-sharp instead of stair-stepping
+    // across it. Outside the map is sky.
+    var t_enter = 0.0;
+    var t_exit = 1.0e30;
+    var inside = true;
+    if (abs(dir.x) < 1e-6) {
+        inside = (cam.x >= 0.0 && cam.x <= world_w);
+    } else {
+        let a = (0.0 - cam.x) / dir.x;
+        let b = (world_w - cam.x) / dir.x;
+        t_enter = max(t_enter, min(a, b));
+        t_exit = min(t_exit, max(a, b));
+    }
+    if (inside) {
+        if (abs(dir.y) < 1e-6) {
+            inside = (cam.y >= 0.0 && cam.y <= world_h);
+        } else {
+            let a = (0.0 - cam.y) / dir.y;
+            let b = (world_h - cam.y) / dir.y;
+            t_enter = max(t_enter, min(a, b));
+            t_exit = min(t_exit, max(a, b));
+        }
+    }
+    if (!inside || t_exit <= 0.0) {
+        return vec4<f32>(apply_underwater(sky_color(dir), 0.0, cam.z, params_uniform().z), 1.0);
+    }
+
+    // March the heightfield cell by cell: the step is never longer than the
+    // time to cross one cell (dominant horizontal axis), while a clearance term
+    // lets the ray skip the empty air above the surface. Resolving every cell is
+    // what keeps cliff and map-edge silhouettes from quantising into huge
+    // stair-steps that crawl as the camera pans.
+    let horiz = max(abs(dir.x), abs(dir.y));
+    let cell_step = min(CELL / max(horiz, 1e-4), CELL * 32.0);
+    var t = max(t_enter, CELL * 0.5);
     var prev = t;
     var hit = false;
     var hit_t = 0.0;
-    for (var i = 0; i < 256 && t < 20000.0; i = i + 1) {
+    for (var i = 0; i < 1024 && t <= t_exit; i = i + 1) {
         let w = cam + dir * t;
-        if (w.x < 0.0 || w.y < 0.0 || w.x >= world_w || w.y >= world_h) {
-            prev = t;
-            dt *= 1.10;
-            t += dt;
-            continue;
-        }
-        if (params_uniform().w > 0.5 && w.z <= params_uniform().z) {
-            hit = true;
-            hit_t = t;
-            break;
-        }
-        if (w.z <= world_height(w.x, w.y)) {
+        let h = world_height(w.x, w.y);
+        let surface = select(h, max(h, params_uniform().z), params_uniform().w > 0.5);
+        if (w.z <= surface) {
             hit = true;
             hit_t = t;
             break;
         }
+        let clearance = (w.z - surface) / max(-dir.z, 1e-4);
         prev = t;
-        dt *= 1.10;
-        t += dt;
+        t += clamp(clearance, cell_step, cell_step * 8.0);
     }
     if (!hit) {
-        return vec4<f32>(sky_color(dir), 1.0);
+        return vec4<f32>(apply_underwater(sky_color(dir), 0.0, cam.z, params_uniform().z), 1.0);
     }
 
+    // Refine the first crossing; with a sub-cell bracket this converges to the
+    // exact surface point.
     var lo = prev;
     var hi = hit_t;
-    for (var i = 0; i < 6; i = i + 1) {
+    for (var i = 0; i < 18; i = i + 1) {
         let mid = 0.5 * (lo + hi);
         let w = cam + dir * mid;
-        let water = params_uniform().w > 0.5 && w.z <= params_uniform().z;
-        if (water || w.z <= world_height(w.x, w.y)) {
+        let h = world_height(w.x, w.y);
+        let surface = select(h, max(h, params_uniform().z), params_uniform().w > 0.5);
+        if (w.z <= surface) {
             hi = mid;
         } else {
             lo = mid;
@@ -178,20 +296,7 @@ fn fs_main(in: TerrainOut) -> @location(0) vec4<f32> {
     let ambient = sun_uniform().w;
 
     if (params_uniform().w > 0.5 && hitpos.z <= params_uniform().z + 0.01) {
-        let time = misc_uniform().x;
-        let q = hitpos.xy * 0.015;
-        let nx = sin(q.x * 1.3 + time * 1.7) + 0.5 * sin(q.x * 3.1 - time * 2.3);
-        let ny = sin(q.y * 1.1 - time * 1.3) + 0.5 * sin(q.y * 2.7 + time * 1.9);
-        let n = normalize(vec3<f32>(nx * 0.06, ny * 0.06, 1.0));
-        let fres = pow(1.0 - clamp(-dir.z, 0.0, 1.0), 3.0);
-        let deep = vec3<f32>(0.03, 0.16, 0.28);
-        let refl = sky_color(reflect(dir, n));
-        let lam = max(0.0, dot(n, sun));
-        var water = mix(deep, refl, clamp(0.25 + 0.55 * fres, 0.0, 0.9));
-        water += vec3<f32>(1.0, 0.98, 0.9) * pow(lam, 64.0) * 0.6;
-        let wfog = clamp(1.0 - exp(-hi * 0.00009), 0.0, 0.75);
-        water = mix(water, sky_color(vec3<f32>(dir.x, dir.y, 0.0)), wfog);
-        return vec4<f32>(water, 1.0);
+        return vec4<f32>(apply_underwater(water_shade(hitpos, dir, hi), hi, cam.z, params_uniform().z), 1.0);
     }
 
     let wx = hitpos.x / CELL;
@@ -225,5 +330,5 @@ fn fs_main(in: TerrainOut) -> @location(0) vec4<f32> {
     var lit = albedo * (ambient + (1.0 - ambient) * lambert);
     let fog = clamp(1.0 - exp(-hi * 0.00009), 0.0, 0.75);
     lit = mix(lit, sky_color(vec3<f32>(dir.x, dir.y, 0.0)), fog);
-    return vec4<f32>(lit, 1.0);
+    return vec4<f32>(apply_underwater(lit, hi, cam.z, params_uniform().z), 1.0);
 }

src/client/ra3.client.cppm

@@ -277,13 +277,15 @@ export namespace ra3::client {
                     } else if (event.type == ui_event_type::mouse_move) {
                         mouse_x = event.x;
                         mouse_y = event.y;
-                        if (event.left) {
+                        if (event.middle) {
                             drag_x += event.dx;
                             drag_y += event.dy;
                         }
                     } else if (event.type == ui_event_type::wheel) {
-                        camera.height = std::clamp(camera.height * (event.wheel > 0.0F ? (1.0F / 1.15F) : 1.15F), camera.min_height, camera.max_height);
-                        dirty = true;
+                        if (event.wheel != 0.0F) {
+                            camera.height = std::clamp(camera.height * (event.wheel > 0.0F ? (1.0F / 1.15F) : 1.15F), camera.min_height, camera.max_height);
+                            dirty = true;
+                        }
                     }
                 }
                 if (!running) break;
@@ -345,8 +347,9 @@ export namespace ra3::client {
         /**
          * GPU terrain viewer. `present_terrain` draws the heightfield; the loop
          * here owns the camera controls. The top-left shows the FPS (current /
-         * cap) and, when `minimap_overview` is not empty, a corner minimap with
-         * the camera location is drawn.
+         * cap) tagged with the active backend name (e.g. `[vulkan]`) and, when
+         * `minimap_overview` is not empty, a corner minimap with the camera
+         * location is drawn.
          */
         [[nodiscard]] auto terrain_loop(const ra3::terrain::gpu_terrain &terrain, ra3::render::camera3d camera, const image &minimap_overview) -> bool {
             if (terrain.width == 0U || terrain.height == 0U || !this->supports_terrain()) return false;
@@ -372,6 +375,7 @@ export namespace ra3::client {
             bool presented = false;
             const auto default_camera = camera;
             bool middle_dragged = false;
+            bool middle_down = false;
             while (running) {
                 ui_event event;
                 float drag_x = 0.0F;
@@ -398,15 +402,23 @@ export namespace ra3::client {
                             if (event.dx != 0.0F || event.dy != 0.0F) middle_dragged = true;
                         }
                     } else if (event.type == ui_event_type::wheel) {
-                        camera.height = std::clamp(camera.height * (event.wheel > 0.0F ? (1.0F / 1.15F) : 1.15F), camera.min_height, camera.max_height);
-                        camera_moved = true;
-                    } else if (event.type == ui_event_type::mouse_button && event.middle && event.released) {
-                        if (!middle_dragged) {
-                            camera.yaw = default_camera.yaw;
-                            camera.pitch = default_camera.pitch;
-                            camera.height = default_camera.height;
+                        if (event.wheel != 0.0F) {
+                            camera.height = std::clamp(camera.height * (event.wheel > 0.0F ? (1.0F / 1.15F) : 1.15F), camera.min_height, camera.max_height);
                             camera_moved = true;
                         }
+                    } else if (event.type == ui_event_type::mouse_button && event.middle) {
+                        if (event.released) {
+                            if (middle_down && !middle_dragged) {
+                                camera.yaw = default_camera.yaw;
+                                camera.pitch = default_camera.pitch;
+                                camera.height = default_camera.height;
+                                camera_moved = true;
+                            }
+                            middle_down = false;
+                        } else {
+                            middle_down = true;
+                            middle_dragged = false;
+                        }
                     }
                 }
                 if (!running) break;
@@ -466,7 +478,7 @@ export namespace ra3::client {
                         fps = static_cast<uint32>(std::lround(static_cast<float>(fps_frames) / window_s));
                         fps_frames = 0;
                         fps_window = now;
-                        overlay.label = ra3::render::compose_fps_label(fps, fps_limit_);
+                        overlay.label = ra3::render::compose_fps_label(fps, fps_limit_, this->name());
                         overlay.label_changed = true;
                     }
                 } else {

src/fs/ra3.fs.cppm

@@ -3,13 +3,16 @@ export module ra3.fs;
 import std;
 
 export import ra3.core;
+import ra3.assets;
 
 /**
  * Reading of the retail game's on-disk assets.
  *
  * Red Alert 3 ships its data in `BIG4` archives under `<install>\Data`, with
- * individual payloads compressed by EA's RefPack codec. This module implements
- * the container and codec so OpenRA3 can read a user's own installation.
+ * individual payloads compressed by EA's RefPack codec. The container and codec
+ * are implemented by the vendored `libra3assets` (`ra3.assets`, a sibling of
+ * `libenderlog`); this module is the thin adapter OpenRA3's loader talks to, so
+ * the format knowledge lives in one place.
  *
  * No game data is ever written into the repository; callers point the loader at
  * their local install (`--game-dir` / `RA3_GAME_DIR`, default `C:\Red Alert 3`).
@@ -42,11 +45,21 @@ export namespace ra3::fs {
         uint32 size = 0;
     };
 
-    /** True when `data` starts with a RefPack header (`0b??010000`, `0xFB`). */
-    [[nodiscard]] inline auto is_refpack(std::span<const uint8> data) -> bool {
-        return data.size() >= 2 && (data[0] & refpack_mask) == 0x10U && data[1] == refpack_magic2;
+    namespace detail {
+        /** View a `uint8` range as bytes, the currency of `libra3assets`. */
+        [[nodiscard]] inline auto as_bytes(std::span<const uint8> data) -> std::span<const std::byte> { return std::as_bytes(data); }
+
+        /** Copy a `libra3assets` byte buffer into OpenRA3's `uint8` vector. */
+        [[nodiscard]] inline auto to_u8(std::vector<std::byte> bytes) -> std::vector<uint8> {
+            std::vector<uint8> out(bytes.size());
+            if (!bytes.empty()) std::memcpy(out.data(), bytes.data(), bytes.size());
+            return out;
+        }
     }
 
+    /** True when `data` starts with a RefPack header (`0b??010000`, `0xFB`). */
+    [[nodiscard]] inline auto is_refpack(std::span<const uint8> data) -> bool { return ra3::assets::is_refpack(detail::as_bytes(data)); }
+
     /**
      * Decompress an EA RefPack stream.
      *
@@ -55,80 +68,17 @@ export namespace ra3::fs {
      * @throws refpack_error if the stream is malformed or the length disagrees.
      */
     [[nodiscard]] inline auto refpack_decompress(std::span<const uint8> data) -> std::vector<uint8> {
-        if (!is_refpack(data)) throw refpack_error("not a RefPack stream");
-
-        usize pos = 0;
-        const auto header = data[pos++];
-        const bool large_files = (header & 0x80U) != 0;
-        const bool compressed_size_present = (header & 0x01U) != 0;
-        pos++; // 0xFB
-
-        const usize size_bytes = large_files ? 4U : 3U;
-        auto read_size = [&]() -> uint32 {
-            uint32 value = 0;
-            for (usize i = 0; i < size_bytes; ++i) {
-                if (pos >= data.size()) throw refpack_error("truncated RefPack size field");
-                value = (value << 8) | data[pos++];
-            }
-            return value;
-        };
-
-        if (compressed_size_present) (void)read_size();
-        const auto out_len = read_size();
-
-        std::vector<uint8> out;
-        out.reserve(out_len);
-
-        auto copy_literals = [&](usize count) {
-            if (pos + count > data.size()) throw refpack_error("truncated RefPack literals");
-            out.insert(out.end(), data.begin() + static_cast<std::ptrdiff_t>(pos), data.begin() + static_cast<std::ptrdiff_t>(pos + count));
-            pos += count;
-        };
-
-        auto copy_reference = [&](usize length, usize distance) {
-            if (distance == 0 || distance > out.size()) throw refpack_error("RefPack back-reference out of range");
-            usize start = out.size() - distance;
-            for (usize i = 0; i < length; ++i) out.push_back(out[start + i]);
-        };
-
-        while (pos < data.size()) {
-            const auto cmd = data[pos++];
-            if ((cmd & 0x80U) == 0) { // 2-byte command
-                if (pos >= data.size()) throw refpack_error("truncated 2-byte command");
-                const auto b2 = data[pos++];
-                copy_literals(cmd & 0x03U);
-                copy_reference(((cmd & 0x1CU) >> 2) + 3, ((cmd & 0x60U) << 3) + b2 + 1);
-            } else if ((cmd & 0x40U) == 0) { // 3-byte command
-                if (pos + 1 >= data.size()) throw refpack_error("truncated 3-byte command");
-                const auto b2 = data[pos];
-                const auto b3 = data[pos + 1];
-                pos += 2;
-                copy_literals((b2 & 0xC0U) >> 6);
-                copy_reference((cmd & 0x3FU) + 4, ((b2 & 0x3FU) << 8) + b3 + 1);
-            } else if ((cmd & 0x20U) == 0) { // 4-byte command
-                if (pos + 2 >= data.size()) throw refpack_error("truncated 4-byte command");
-                const auto b2 = data[pos];
-                const auto b3 = data[pos + 1];
-                const auto b4 = data[pos + 2];
-                pos += 3;
-                copy_literals(cmd & 0x03U);
-                copy_reference(((cmd & 0x0CU) << 6) + b4 + 5, ((cmd & 0x10U) << 12) + (b2 << 8) + b3 + 1);
-            } else if (cmd < 0xFCU) { // long literal run
-                copy_literals(((cmd & 0x1FU) + 1) << 2);
-            } else { // stop
-                copy_literals(cmd & 0x03U);
-                break;
-            }
+        try {
+            return detail::to_u8(ra3::assets::refpack_decompress(detail::as_bytes(data)));
+        } catch (const ra3::assets::refpack_error &error) {
+            throw refpack_error(error.what());
         }
-
-        if (out.size() != out_len) throw refpack_error("RefPack length mismatch");
-        return out;
     }
 
     /** Decompress `data` when it is RefPack, otherwise copy it unchanged. */
     [[nodiscard]] inline auto maybe_decompress(std::span<const uint8> data) -> std::vector<uint8> {
-        if (is_refpack(data)) return refpack_decompress(data);
-        return {data.begin(), data.end()};
+        if (!is_refpack(data)) return {data.begin(), data.end()};
+        return refpack_decompress(data);
     }
 
     /**
@@ -137,23 +87,11 @@ export namespace ra3::fs {
      * @throws refpack_error if the stream is malformed.
      */
     [[nodiscard]] inline auto refpack_output_size(std::span<const uint8> data) -> uint32 {
-        if (!is_refpack(data)) throw refpack_error("not a RefPack stream");
-        usize pos = 0;
-        const auto header = data[pos++];
-        const bool large_files = (header & 0x80U) != 0;
-        const bool compressed_size_present = (header & 0x01U) != 0;
-        pos++; // 0xFB
-        const usize size_bytes = large_files ? 4U : 3U;
-        auto read_size = [&]() -> uint32 {
-            uint32 value = 0;
-            for (usize i = 0; i < size_bytes; ++i) {
-                if (pos >= data.size()) throw refpack_error("truncated RefPack size field");
-                value = (value << 8) | data[pos++];
-            }
-            return value;
-        };
-        if (compressed_size_present) (void)read_size();
-        return read_size();
+        try {
+            return ra3::assets::refpack_output_size(detail::as_bytes(data));
+        } catch (const ra3::assets::refpack_error &error) {
+            throw refpack_error(error.what());
+        }
     }
 
     [[nodiscard]] constexpr auto read_be32(const uint8 *p) -> uint32 {
@@ -165,81 +103,32 @@ export namespace ra3::fs {
     }
 
     /**
-     * A parsed `BIG4` archive. Only the index is held in memory; payloads are
-     * read from disk on demand so multi-hundred-megabyte archives stay cheap.
+     * A parsed `BIG4` archive.
+     *
+     * The index and payloads are held by a `ra3::assets::big_archive`; this
+     * adapter exposes the OpenRA3-facing surface (`big_entry`, `uint8` buffers)
+     * over it. Payloads are RefPack-decompressed on request.
      */
     class big_archive {
     public:
         /**
-         * Parse the index of a `BIG4` archive.
+         * Parse a `BIG4` archive.
          *
          * @param path Archive path.
          * @throws archive_error if the file is missing, not `BIG4`, or truncated.
          */
         [[nodiscard]] static auto open(const std::filesystem::path &path) -> big_archive {
-            big_archive archive;
-            archive.path_ = path;
-            std::error_code ec;
-            archive.file_size_ = static_cast<usize>(std::filesystem::file_size(path, ec));
-            if (ec) throw archive_error("cannot stat archive: " + path.string());
-
-            std::ifstream in(path, std::ios::binary);
-            if (!in) throw archive_error("cannot open archive: " + path.string());
-
-            std::array<uint8, 16> header{};
-            in.read(reinterpret_cast<char *>(header.data()), static_cast<std::streamsize>(header.size()));
-            if (!in || std::memcmp(header.data(), big_magic.data(), big_magic.size()) != 0) throw archive_error("not a BIG4 archive: " + path.string());
-
-            const auto count = read_be32(header.data() + 8);
-
-            // Read the variable-length index, growing the window until parsed.
-            usize window = std::min(archive.file_size_, std::max<usize>(1U << 20U, static_cast<usize>(count) * 256U));
-            std::vector<uint8> index;
-            for (;;) {
-                index.resize(window);
-                in.clear();
-                in.seekg(0);
-                in.read(reinterpret_cast<char *>(index.data()), static_cast<std::streamsize>(window));
-                const auto got = static_cast<usize>(in.gcount());
-                index.resize(got);
-
-                archive.entries_.clear();
-                archive.entries_.reserve(count);
-                usize pos = 16;
-                bool complete = true;
-                for (uint32 i = 0; i < count; ++i) {
-                    if (pos + 8 > index.size()) {
-                        complete = false;
-                        break;
-                    }
-                    big_entry entry;
-                    entry.offset = read_be32(index.data() + pos);
-                    entry.size = read_be32(index.data() + pos + 4);
-                    pos += 8;
-                    const auto *begin = reinterpret_cast<const char *>(index.data() + pos);
-                    const auto *end = reinterpret_cast<const char *>(std::memchr(begin, '\0', index.size() - pos));
-                    if (end == nullptr) {
-                        complete = false;
-                        break;
-                    }
-                    entry.name.assign(begin, end);
-                    pos += static_cast<usize>(end - begin) + 1U;
-                    archive.entries_.push_back(std::move(entry));
-                }
-                if (complete) break;
-                if (window >= archive.file_size_) throw archive_error("truncated BIG4 index: " + path.string());
-                window = std::min(archive.file_size_, window * 2U);
+            try {
+                return big_archive{ra3::assets::big_archive::open(path), path};
+            } catch (const ra3::assets::asset_error &error) {
+                throw archive_error(error.what());
             }
-
-            archive.index_.reserve(archive.entries_.size());
-            for (usize i = 0; i < archive.entries_.size(); ++i) archive.index_.emplace(archive.entries_[i].name, i);
-            return archive;
         }
 
         [[nodiscard]] auto path() const -> const std::filesystem::path & { return path_; }
         [[nodiscard]] auto entries() const -> const std::vector<big_entry> & { return entries_; }
         [[nodiscard]] auto size() const -> usize { return entries_.size(); }
-        [[nodiscard]] auto contains(std::string_view name) const -> bool { return index_.contains(std::string{name}); }
+        [[nodiscard]] auto contains(std::string_view name) const -> bool { return archive_.contains(name); }
 
         /** Entry names whose path contains `needle`, in index order. */
         [[nodiscard]] auto find(std::string_view needle) const -> std::vector<const big_entry *> {
@@ -258,42 +147,33 @@ export namespace ra3::fs {
          * @throws archive_error if the entry is missing or unreadable.
          */
         [[nodiscard]] auto read(std::string_view name, bool decompress = true) const -> std::vector<uint8> {
-            const auto it = index_.find(std::string{name});
-            if (it == index_.end()) throw archive_error("no such entry: " + std::string{name});
-            const auto &entry = entries_[it->second];
-
-            std::ifstream in(path_, std::ios::binary);
-            if (!in) throw archive_error("cannot open archive: " + path_.string());
-            in.seekg(static_cast<std::streamoff>(entry.offset));
-            std::vector<uint8> raw(entry.size);
-            in.read(reinterpret_cast<char *>(raw.data()), static_cast<std::streamsize>(raw.size()));
-            if (!in) throw archive_error("short read for entry: " + entry.name);
-            return decompress ? maybe_decompress(raw) : raw;
+            try {
+                return detail::to_u8(archive_.read(name, decompress));
+            } catch (const ra3::assets::refpack_error &error) {
+                throw refpack_error(error.what());
+            } catch (const ra3::assets::asset_error &error) {
+                throw archive_error(error.what());
+            }
         }
 
         /** Read the first `count` stored bytes of an entry (no decompression). */
         [[nodiscard]] auto read_prefix(std::string_view name, usize count) const -> std::vector<uint8> {
-            const auto it = index_.find(std::string{name});
-            if (it == index_.end()) throw archive_error("no such entry: " + std::string{name});
-            const auto &entry = entries_[it->second];
-
-            std::ifstream in(path_, std::ios::binary);
-            if (!in) throw archive_error("cannot open archive: " + path_.string());
-            in.seekg(static_cast<std::streamoff>(entry.offset));
-            const auto want = std::min(count, static_cast<usize>(entry.size));
-            std::vector<uint8> raw(want);
-            in.read(reinterpret_cast<char *>(raw.data()), static_cast<std::streamsize>(raw.size()));
-            raw.resize(static_cast<usize>(in.gcount()));
-            return raw;
+            try {
+                return detail::to_u8(archive_.read_prefix(name, count));
+            } catch (const ra3::assets::asset_error &error) {
+                throw archive_error(error.what());
+            }
         }
 
     private:
-        big_archive() = default;
+        big_archive(ra3::assets::big_archive archive, std::filesystem::path path) : archive_(std::move(archive)), path_(std::move(path)) {
+            entries_.reserve(archive_.size());
+            for (const auto &entry: archive_.entries()) entries_.push_back({entry.name, entry.offset, entry.size});
+        }
 
+        ra3::assets::big_archive archive_;
         std::filesystem::path path_;
-        usize file_size_ = 0;
         std::vector<big_entry> entries_;
-        std::unordered_map<std::string, usize> index_;
     };
 
     /**
@@ -306,18 +186,6 @@ export namespace ra3::fs {
      * @return The install root, or `std::nullopt` when none is found.
      */
     [[nodiscard]] inline auto find_game_dir(const std::optional<std::filesystem::path> &explicit_dir = std::nullopt) -> std::optional<std::filesystem::path> {
-        auto qualifies = [](const std::filesystem::path &candidate) {
-            std::error_code ec;
-            return !candidate.empty() && std::filesystem::is_directory(candidate / "Data", ec);
-        };
-
-        if (explicit_dir && qualifies(*explicit_dir)) return explicit_dir;
-        if (const auto *env = std::getenv("RA3_GAME_DIR"); env != nullptr && *env != '\0') {
-            const std::filesystem::path candidate{env};
-            if (qualifies(candidate)) return candidate;
-        }
-        const std::filesystem::path default_dir{"C:/Red Alert 3"};
-        if (qualifies(default_dir)) return default_dir;
-        return std::nullopt;
+        return ra3::assets::find_game_dir(explicit_dir);
     }
 }

src/map/ra3.map.cppm

@@ -4,6 +4,7 @@ import std;
 
 export import ra3.core;
 export import ra3.fs;
+import ra3.assets;
 
 /**
  * Red Alert 3 map discovery and loading.
@@ -50,6 +51,9 @@ export namespace ra3::map {
     };
 
     namespace detail {
+        /** View a `uint8` range as bytes, the currency of `libra3assets`. */
+        [[nodiscard]] inline auto as_bytes(std::span<const uint8> data) -> std::span<const std::byte> { return std::as_bytes(data); }
+
         [[nodiscard]] inline auto split_path(std::string_view path) -> std::vector<std::string> {
             std::vector<std::string> parts;
             usize start = 0;
@@ -82,54 +86,6 @@ export namespace ra3::map {
             return file;
         }
 
-        [[nodiscard]] inline auto find_bytes(std::span<const uint8> haystack, std::string_view needle) -> usize {
-            if (needle.empty()) return 0;
-            const auto *needle_begin = reinterpret_cast<const uint8 *>(needle.data());
-            const auto it = std::search(haystack.begin(), haystack.end(), needle_begin, needle_begin + needle.size());
-            return it == haystack.end() ? static_cast<usize>(-1) : static_cast<usize>(it - haystack.begin());
-        }
-
-        [[nodiscard]] inline auto read_le_f32(const uint8 *p) -> real {
-            const auto bits = fs::read_le32(p);
-            real value = 0.0F;
-            std::memcpy(&value, &bits, sizeof(value));
-            return value;
-        }
-
-        /** First plausible `(x, y, 0)` float triple at or after `from`. */
-        [[nodiscard]] inline auto scan_triple(std::span<const uint8> data, usize from, usize window) -> std::optional<start_position> {
-            const auto end = std::min(data.size(), from + window);
-            for (usize p = from; p + 12U <= end; ++p) {
-                const auto x = read_le_f32(data.data() + p);
-                const auto y = read_le_f32(data.data() + p + 4U);
-                const auto z = read_le_f32(data.data() + p + 8U);
-                if (z == 0.0F && std::isfinite(x) && std::isfinite(y) && x > 0.0F && x < 20000.0F && y > 0.0F && y < 20000.0F) {
-                    return start_position{x, y, z};
-                }
-            }
-            return std::nullopt;
-        }
-
-        /** Extract `Player_1_Start` .. `Player_N_Start` waypoint coordinates. */
-        [[nodiscard]] inline auto extract_start_positions(std::span<const uint8> ckmp, int max_players = 8) -> std::vector<start_position> {
-            std::vector<start_position> result;
-            for (int n = 1; n <= max_players; ++n) {
-                const auto needle = std::string{"Player_"} + std::to_string(n) + "_Start";
-                usize cursor = 0;
-                while (cursor < ckmp.size()) {
-                    const auto at = find_bytes(ckmp.subspan(cursor), needle);
-                    if (at == static_cast<usize>(-1)) break;
-                    const auto abs = cursor + at;
-                    if (const auto triple = scan_triple(ckmp, abs + needle.size(), 128); triple) {
-                        result.push_back(*triple);
-                        break;
-                    }
-                    cursor = abs + 1;
-                }
-            }
-            return result;
-        }
-
         /** Number of distinct integer positions (used to reject degenerate sets). */
         [[nodiscard]] inline auto distinct_positions(const std::vector<start_position> &starts) -> usize {
             std::vector<std::pair<int, int>> seen;
@@ -196,9 +152,24 @@ export namespace ra3::map {
         return fs::maybe_decompress(payload);
     }
 
-    /** Recover `Player_N_Start` waypoints from raw, uncompressed `CkMp` bytes. */
+    /**
+     * Recover `Player_N_Start` waypoints from raw, uncompressed `CkMp` bytes.
+     *
+     * `libra3assets` decodes the `ObjectsList` `*Waypoints/Waypoint` objects and
+     * returns the position of each `waypointName == "Player_<n>_Start"`. This
+     * replaces the previous whole-buffer heuristic, which scanned for the string
+     * and then took the first plausible float triple *after* it — off by one
+     * (the position precedes the name in each object) and prone to matching
+     * arbitrary bytes.
+     */
     [[nodiscard]] inline auto starts_from_ckmp(std::span<const uint8> ckmp) -> std::vector<start_position> {
-        auto starts = detail::extract_start_positions(ckmp);
+        std::vector<start_position> starts;
+        try {
+            const auto document = ra3::assets::map_document::parse(detail::as_bytes(ckmp));
+            for (const auto &start: document.player_starts()) starts.push_back({start.position.x, start.position.y, start.position.z});
+        } catch (const std::exception &) {
+            return {};
+        }
         if (detail::distinct_positions(starts) < 2U) starts.clear();
         return starts;
     }
@@ -221,117 +192,34 @@ export namespace ra3::map {
         uint32 road_type = 0U; ///< SAGE `RoadType` flags; 0 for a non-road object.
     };
 
-    namespace detail {
-        struct ckmp_chunk {
-            std::string name;
-            uint16 version = 0;
-            usize offset = 0;
-            usize size = 0;
-        };
-
-        /** Parse the `CkMp` chunk tree and its `index -> name` table. */
-        [[nodiscard]] inline auto parse_ckmp_chunks(std::span<const uint8> data) -> std::pair<std::vector<std::string>, std::vector<ckmp_chunk>> {
-            if (data.size() < 8U || std::memcmp(data.data(), "CkMp", 4) != 0) return {};
-            usize pos = 4;
-            const auto read_u32 = [&](usize at) {
-                return static_cast<uint32>(data[at]) | (static_cast<uint32>(data[at + 1U]) << 8U) | (static_cast<uint32>(data[at + 2U]) << 16U) |
-                       (static_cast<uint32>(data[at + 3U]) << 24U);
-            };
-            const auto read_u16 = [&](usize at) { return static_cast<uint16>(static_cast<uint32>(data[at]) | (static_cast<uint32>(data[at + 1U]) << 8U)); };
-            const auto count = read_u32(pos);
-            pos += 4;
-            std::vector<std::string> names(count + 1U);
-            for (uint32 i = count; i >= 1U && pos < data.size(); --i) {
-                const auto len = data[pos++];
-                if (pos + len + 4U > data.size()) break;
-                names[i] = std::string{reinterpret_cast<const char *>(data.data() + pos), len};
-                pos += len + 4U;
-            }
-            std::vector<ckmp_chunk> chunks;
-            while (pos + 10U <= data.size()) {
-                const auto index = read_u32(pos);
-                const auto version = read_u16(pos + 4U);
-                const auto size = read_u32(pos + 6U);
-                pos += 10U;
-                if (index >= names.size() || pos + size > data.size()) break;
-                chunks.push_back({names[index], version, pos, size});
-                pos += size;
-            }
-            return {std::move(names), std::move(chunks)};
-        }
-    }
-
     /**
      * Every object the map places (the `ObjectsList` chunk).
      *
-     * Layout (OpenSAGE `Data/Map/{ObjectsList,MapObject,AssetProperty}.cs`):
-     * the chunk is a list of nested `Object` assets, each a `Coord3D`, a Z
-     * `angle`, a `RoadType`, a `u16`-prefixed type-name and a property list
-     * whose keys index the shared name table.
+     * Decoded by `libra3assets` (`ra3.assets`): the map is parsed as a
+     * `map_document`, whose `ObjectsList` accessor walks the nested `Object`
+     * assets (a `Coord3D`, a Z `angle`, a `RoadType`, a `u16`-prefixed
+     * type-name and a property list keyed into the shared name table).
      *
-     * @return The objects in chunk order; empty when the map has no object list.
+     * @return The objects in chunk order; empty when the map is malformed or has
+     *         no object list.
      */
     [[nodiscard]] inline auto parse_objects(std::span<const uint8> ckmp) -> std::vector<map_object> {
-        const auto [names, chunks] = detail::parse_ckmp_chunks(ckmp);
-        (void) names;
         std::vector<map_object> objects;
-        const auto read_u16 = [&](usize at) { return static_cast<uint16>(static_cast<uint32>(ckmp[at]) | (static_cast<uint32>(ckmp[at + 1U]) << 8U)); };
-        const auto read_u32 = [&](usize at) {
-            return static_cast<uint32>(ckmp[at]) | (static_cast<uint32>(ckmp[at + 1U]) << 8U) | (static_cast<uint32>(ckmp[at + 2U]) << 16U) |
-                   (static_cast<uint32>(ckmp[at + 3U]) << 24U);
-        };
-        const auto read_f32 = [&](usize at) {
-            const auto bits = read_u32(at);
-            real value = 0.0F;
-            std::memcpy(&value, &bits, sizeof(value));
-            return value;
-        };
-
-        for (const auto &chunk: chunks) {
-            if (chunk.name != "ObjectsList") continue;
-            usize p = chunk.offset;
-            const auto end = chunk.offset + chunk.size;
-            while (p + 6U <= end) {
-                p += 4U; // asset index (always `Object`)
-                p += 2U; // asset version
-                const auto asset_size = read_u32(p);
-                p += 4U;
-                if (asset_size < 24U || p + asset_size > end) break;
-                const auto asset_end = p + asset_size;
-
-                map_object object;
-                object.x = read_f32(p);
-                object.y = read_f32(p + 4U);
-                object.z = read_f32(p + 8U);
-                object.angle = read_f32(p + 12U);
-                object.road_type = read_u32(p + 16U);
-                p += 20U; // Coord3D + angle + road type
-                const auto name_len = read_u16(p);
-                p += 2U;
-                if (p + name_len > asset_end) break;
-                object.type = std::string{reinterpret_cast<const char *>(ckmp.data() + p), name_len};
-                p += name_len;
-
-                const auto property_count = static_cast<uint32>(read_u16(p));
-                p += 2U;
-                for (uint32 i = 0; i < property_count && p + 4U <= asset_end; ++i) {
-                    const auto type = ckmp[p++];
-                    p += 3U; // property name index (u24) into the shared name table
-                    usize value_size = 0;
-                    if (type == 0U) {
-                        value_size = 1U; // boolean
-                    } else if (type == 1U || type == 2U) {
-                        value_size = 4U; // integer / real
-                    } else if (p + 2U <= asset_end) {
-                        const auto len = read_u16(p);
-                        value_size = 2U + static_cast<usize>(len) * ((type == 4U) ? 2U : 1U); // ascii/unicode/unknown
-                    }
-                    p += value_size;
-                    if (p > asset_end) break;
-                }
-                objects.push_back(std::move(object));
-                p = asset_end;
+        try {
+            const auto document = ra3::assets::map_document::parse(detail::as_bytes(ckmp));
+            for (const auto &object: document.objects()) {
+                map_object out;
+                out.type = object.type_name;
+                out.x = object.position.x;
+                out.y = object.position.y;
+                out.z = object.position.z;
+                out.angle = object.angle;
+                out.scale = 1.0F;
+                out.road_type = static_cast<uint32>(object.road);
+                objects.push_back(std::move(out));
             }
+        } catch (const std::exception &) {
+            return {};
         }
         return objects;
     }
@@ -351,96 +239,30 @@ export namespace ra3::map {
         }
     };
 
-    namespace detail {
-        /**
-         * Decode one SAGE `.csf` string value.
-         *
-         * RA3's `gamestrings.csf` stores each UTF-16 code unit with the low byte
-         * XORed by `0xFF` (the high byte is the padding `0xFF`); undoing that
-         * yields the plain ASCII/UTF-8 text.
-         */
-        [[nodiscard]] inline auto decode_csf_string(std::span<const uint8> raw) -> std::string {
-            std::string value;
-            for (usize i = 0; i + 1U < raw.size(); i += 2U) {
-                const auto ch = static_cast<char>(static_cast<uint8>(raw[i] ^ 0xFFU));
-                if (ch == '\0') break;
-                value.push_back(ch);
-            }
-            return value;
-        }
-    }
-
     /**
      * Parse `MAP:<id>` display names out of a SAGE `.csf` string table.
      *
      * The map list UI reads its labels from the install's `data\gamestrings.csf`
      * under the key `MAP:<UPPERCASE_ID>` (e.g. `MAP:MAP_MP_2_FEASEL4` is
-     * "Battlebase Beta"). Values are byte-XORed with `0xFF`.
+     * "Battlebase Beta"). Decoding is `libra3assets`' `csf_table` (each UTF-16
+     * code unit is bit-inverted; the table lookup is case-insensitive).
      */
     [[nodiscard]] inline auto parse_map_names(std::span<const uint8> csf) -> map_name_table {
         map_name_table table;
-        if (csf.size() < 24U || std::memcmp(csf.data(), " FSC", 4) != 0) return table;
-
-        const auto read = [&](usize p) -> uint32 {
-            return static_cast<uint32>(csf[p]) | (static_cast<uint32>(csf[p + 1U]) << 8U) | (static_cast<uint32>(csf[p + 2U]) << 16U) |
-                   (static_cast<uint32>(csf[p + 3U]) << 24U);
-        };
-
-        usize pos = 24; // header: magic + version + label/string counts + 8 reserved bytes
-        while (pos + 4U <= csf.size()) {
-            if (std::memcmp(csf.data() + pos, " LBL", 4) != 0) {
-                ++pos;
-                continue;
-            }
-            pos += 4;
-            if (pos + 4U > csf.size()) break;
-            const auto count = read(pos);
-            pos += 4;
-            std::vector<std::string> labels;
-            labels.reserve(count);
-            bool ok = true;
-            for (uint32 i = 0; i < count; ++i) {
-                if (pos + 4U > csf.size()) {
-                    ok = false;
-                    break;
-                }
-                const auto len = read(pos);
-                pos += 4;
-                if (pos + len > csf.size()) {
-                    ok = false;
-                    break;
-                }
-                labels.emplace_back(reinterpret_cast<const char *>(csf.data() + pos), len);
-                pos += len;
-            }
-            if (!ok) break;
-            for (const auto &label: labels) {
-                if (pos + 4U > csf.size() || std::memcmp(csf.data() + pos, " RTS", 4) != 0) {
-                    ok = false;
-                    break;
-                }
-                pos += 4;
-                if (pos + 4U > csf.size()) {
-                    ok = false;
-                    break;
-                }
-                const auto chars = read(pos);
-                pos += 4;
-                const auto bytes = static_cast<usize>(chars) * 2U;
-                if (pos + bytes > csf.size()) {
-                    ok = false;
-                    break;
-                }
-                auto value = detail::decode_csf_string(csf.subspan(pos, bytes));
-                pos += bytes;
+        try {
+            const auto strings = ra3::assets::csf_table::parse(detail::as_bytes(csf));
+            for (const auto &entry: strings.entries()) {
                 constexpr std::string_view prefix = "MAP:";
-                if (label.size() > prefix.size() && label.compare(0, prefix.size(), prefix) == 0) {
-                    auto id = label.substr(prefix.size());
-                    std::transform(id.begin(), id.end(), id.begin(), [](unsigned char ch) { return static_cast<char>(std::tolower(ch)); });
-                    if (!value.empty()) table.names.try_emplace(std::move(id), std::move(value));
-                }
+                if (entry.label.size() <= prefix.size() || entry.label.compare(0, prefix.size(), prefix) != 0) continue;
+                auto id = entry.label.substr(prefix.size());
+                std::transform(id.begin(), id.end(), id.begin(), [](unsigned char ch) { return static_cast<char>(std::tolower(ch)); });
+                auto value = ra3::assets::utf16_to_utf8(entry.value());
+                // CSF strings are NUL-terminated; the terminator is not part of the text.
+                if (const auto nul = value.find('\0'); nul != std::string::npos) value.resize(nul);
+                if (!value.empty()) table.names.try_emplace(std::move(id), std::move(value));
             }
-            if (!ok) break;
+        } catch (const std::exception &) {
+            return {};
         }
         return table;
     }

src/models/ra3.models.cppm

@@ -765,6 +765,7 @@ export namespace ra3::models {
         usize placed = 0;
         usize missing = 0;
         usize roads = 0;
+        usize hidden = 0; ///< Objects/roads below the water plane, not drawn.
 
         [[nodiscard]] auto empty() const -> bool { return indices.empty(); }
         [[nodiscard]] auto triangle_count() const -> usize { return indices.size() / 3U; }
@@ -823,9 +824,14 @@ export namespace ra3::models {
      * @param ground_height  Terrain height (world Z) at a world `(x, y)`, so
      *                       objects sit on the relief instead of a flat plane.
      * @param texture_size   Edge length of the shared texture array (0 = auto).
+     * @param cull_below_z   Skip placements whose base sits below this world Z
+     *                       (the water plane): an opaque water surface hides
+     *                       submerged objects, so drawing them would float them
+     *                       on top of the sea.
      */
     [[nodiscard]] inline auto build_scene(const asset_stream &stream, std::span<const placement> placements,
-                                          const std::function<float(float, float)> &ground_height = {}, uint32 texture_size = 128U) -> scene {
+                                          const std::function<float(float, float)> &ground_height = {}, uint32 texture_size = 128U,
+                                          float cull_below_z = -3.4e38F) -> scene {
         scene out;
         out.texture_size = texture_size == 0U ? 128U : texture_size;
         std::unordered_map<std::string, uint32> texture_layers;
@@ -972,6 +978,12 @@ export namespace ra3::models {
             if ((a.road_type & 2U) == 0U) continue; // RoadType::Start
             const auto &b = placements[i + 1U];
             if ((b.road_type & 4U) == 0U || b.type != a.type) continue; // RoadType::End
+            const auto road_base = (ground_height ? ground_height(a.x, a.y) : 0.0F) + a.z;
+            if (road_base < cull_below_z) {
+                ++out.hidden;
+                ++i;
+                continue;
+            }
             emit_road(a, b);
             ++i;
         }
@@ -986,6 +998,10 @@ export namespace ra3::models {
             const auto cos_a = std::cos(item.angle);
             const auto sin_a = std::sin(item.angle);
             const auto base_z = (ground_height ? ground_height(item.x, item.y) : 0.0F) + item.z;
+            if (base_z < cull_below_z) {
+                ++out.hidden;
+                continue;
+            }
             bool drawn = false;
             for (const auto *mesh_asset: meshes) {
                 // Only opaque material parts are drawn; meshes with no diffuse

src/render/ra3.render.cppm

@@ -314,10 +314,11 @@ export namespace ra3::render {
     }
 
     /**
-     * A small translucent label for the top-left corner, e.g. `FPS: 155/160`.
-     * `cap == 0` means vertical sync, `cap < 0` means uncapped.
+     * A small translucent label for the top-left corner, e.g.
+     * `FPS: 155/160 [vulkan]`. `cap == 0` means vertical sync, `cap < 0` means
+     * uncapped. `backend` is the active renderer backend name (empty omits it).
      */
-    [[nodiscard]] inline auto compose_fps_label(uint32 fps, int cap) -> image {
+    [[nodiscard]] inline auto compose_fps_label(uint32 fps, int cap, std::string_view backend = {}) -> image {
         char text[64];
         if (cap == 0) {
             std::snprintf(text, sizeof(text), "FPS: %u/vsync", fps);
@@ -326,10 +327,16 @@ export namespace ra3::render {
         } else {
             std::snprintf(text, sizeof(text), "FPS: %u/%d", fps, cap);
         }
-        const auto w = text_width(text, 1U) + 8U;
+        std::string label{text};
+        if (!backend.empty()) {
+            label += " [";
+            label += backend;
+            label += ']';
+        }
+        const auto w = text_width(label, 1U) + 8U;
         const auto h = detail::glyph_height + 6U;
         image img(w, h, argb(30, 6, 6, 200)); // warm translucent backing
-        draw_text(img, 4, 3, text, argb(240, 200, 90), 1U);
+        draw_text(img, 4, 3, label, argb(240, 200, 90), 1U);
         return img;
     }
 

src/terrain/ra3.terrain.cppm

@@ -6,6 +6,7 @@ export import ra3.core;
 export import ra3.fs;
 export import ra3.render;
 export import ra3.models;
+import ra3.assets;
 
 /**
  * The map's real terrain, read from the compiled `CkMp` chunk tree.
@@ -91,82 +92,24 @@ export namespace ra3::terrain {
     };
 
     namespace detail {
+        /** View a `uint8` range as bytes, the currency of `libra3assets`. */
+        [[nodiscard]] inline auto as_bytes(std::span<const uint8> data) -> std::span<const std::byte> { return std::as_bytes(data); }
+
+        /** View a `libra3assets` byte range as OpenRA3's `uint8`. */
+        [[nodiscard]] inline auto as_u8(std::span<const std::byte> data) -> std::span<const uint8> {
+            return {reinterpret_cast<const uint8 *>(data.data()), data.size()};
+        }
+
         [[nodiscard]] inline auto read_u16(const uint8 *p) -> uint16 { return static_cast<uint16>(p[0]) | (static_cast<uint16>(p[1]) << 8U); }
         [[nodiscard]] inline auto read_u32(const uint8 *p) -> uint32 {
             return static_cast<uint32>(p[0]) | (static_cast<uint32>(p[1]) << 8U) | (static_cast<uint32>(p[2]) << 16U) |
                    (static_cast<uint32>(p[3]) << 24U);
         }
 
-        struct chunk {
-            std::string name;
-            uint16 version = 0;
-            usize offset = 0;
-            usize size = 0;
-        };
-
-        /**
-         * Parse the `CkMp` chunk tree into a flat chunk list.
-         *
-         * Layout: `"CkMp"`, `u32 assetCount`, then `assetCount` entries of
-         * `{ u8 nameLen, name, u32 index }` (index descending from the count),
-         * then `{ u32 index, u16 version, u32 dataSize, data[dataSize] }` per
-         * chunk until the end.
-         */
-        [[nodiscard]] inline auto parse_chunks(std::span<const uint8> data) -> std::vector<chunk> {
-            if (data.size() < 8U || std::memcmp(data.data(), "CkMp", 4) != 0) throw terrain_error("not a CkMp map");
-            usize pos = 4;
-            const auto count = read_u32(data.data() + pos);
-            pos += 4;
-
-            std::vector<std::string> names(count + 1U);
-            for (uint32 i = count; i >= 1U; --i) {
-                if (pos >= data.size()) throw terrain_error("truncated asset-name table");
-                const auto len = data[pos++];
-                if (pos + len + 4U > data.size()) throw terrain_error("truncated asset-name");
-                names[i] = std::string{reinterpret_cast<const char *>(data.data() + pos), len};
-                pos += len;
-                pos += 4; // asset index (== i)
-            }
-
-            std::vector<chunk> chunks;
-            while (pos + 10U <= data.size()) {
-                const auto index = read_u32(data.data() + pos);
-                const auto version = read_u16(data.data() + pos + 4U);
-                const auto size = read_u32(data.data() + pos + 6U);
-                pos += 10;
-                if (index >= names.size() || pos + size > data.size()) throw terrain_error("bad chunk header");
-                chunks.push_back({names[index], version, pos, size});
-                pos += size;
-            }
-            return chunks;
-        }
-
-        [[nodiscard]] inline auto find(const std::vector<chunk> &chunks, std::string_view name) -> const chunk * {
-            for (const auto &c: chunks) {
-                if (c.name == name) return &c;
-            }
-            return nullptr;
-        }
-
-        inline auto parse_heightmap(std::span<const uint8> data, const chunk &c, map_data &out) -> void {
-            usize p = c.offset;
-            out.width = read_u32(data.data() + p);
-            out.height = read_u32(data.data() + p + 4U);
-            out.border_width = read_u32(data.data() + p + 8U);
-            const auto border_count = read_u32(data.data() + p + 12U);
-            p += 16;
-            p += static_cast<usize>(border_count) * (c.version >= 6U ? 16U : 8U);
-            p += 4U; // area
-
-            if (out.width == 0U || out.height == 0U) throw terrain_error("empty heightmap");
-            const auto area = static_cast<usize>(out.width) * out.height;
-            out.elevations.resize(area);
-            for (usize i = 0; i < area; ++i) {
-                if (p >= data.size()) throw terrain_error("truncated heightmap");
-                out.elevations[i] = c.version >= 5U ? read_u16(data.data() + p) : data[p];
-                p += c.version >= 5U ? 2U : 1U;
-            }
-        }
+        // The `CkMp` container and `HeightMapData` chunk are modelled by
+        // `libra3assets` (`ra3.assets`); `parse_map` reads them through a
+        // `map_document`. Only `BlendTileData` (which the library does not type
+        // yet) is parsed here, over the chunk payload the document exposes.
 
         /** Where the texture table ends and how many `BlendDescription`s follow. */
         struct texture_table_info {
@@ -246,20 +189,20 @@ export namespace ra3::terrain {
             }
         }
 
-        inline auto parse_blend(std::span<const uint8> data, const chunk &c, map_data &out) -> void {
+        inline auto parse_blend(std::span<const uint8> payload, uint16 version, map_data &out) -> void {
             const auto area = static_cast<usize>(out.width) * out.height;
-            usize p = c.offset;
-            const auto num_tiles = read_u32(data.data() + p);
+            usize p = 0;
+            const auto num_tiles = read_u32(payload.data() + p);
             p += 4;
             if (num_tiles != area) throw terrain_error("BlendTileData tile count mismatch");
             out.tiles.resize(area);
-            for (usize i = 0; i < area; ++i) out.tiles[i] = read_u16(data.data() + p + i * 2U);
+            for (usize i = 0; i < area; ++i) out.tiles[i] = read_u16(payload.data() + p + i * 2U);
             p += area * 2U;
 
-            const auto bits = (c.version >= 14U && c.version < 24U) ? 32U : 16U;
+            const auto bits = (version >= 14U && version < 24U) ? 32U : 16U;
             const auto word = bits / 8U;
             const auto read_index = [&](usize off) -> uint16 {
-                return word == 4U ? static_cast<uint16>(read_u32(data.data() + off)) : read_u16(data.data() + off);
+                return word == 4U ? static_cast<uint16>(read_u32(payload.data() + off)) : read_u16(payload.data() + off);
             };
             out.blends.resize(area);
             for (usize i = 0; i < area; ++i) out.blends[i] = read_index(p + i * word);
@@ -269,38 +212,55 @@ export namespace ra3::terrain {
             p += area * word;
             p += area * word; // CliffTextures (not rendered yet)
 
-            const auto chunk_end = c.offset + c.size;
-            const auto table = parse_textures(data, p, chunk_end, out);
-            parse_blend_descriptions(data, table, chunk_end, out);
+            const auto chunk_end = payload.size();
+            const auto table = parse_textures(payload, p, chunk_end, out);
+            parse_blend_descriptions(payload, table, chunk_end, out);
         }
     }
 
     /**
      * Parse the terrain chunks out of a `CkMp` (uncompressed) map payload.
      *
+     * The container and `HeightMapData` come from `libra3assets`
+     * (`map_document`); `BlendTileData` (which the library does not model yet)
+     * is decoded here from the chunk payload the document exposes.
+     *
      * @throws terrain_error if the chunk tree or terrain chunks are malformed.
      */
     [[nodiscard]] inline auto parse_map(std::span<const uint8> ckmp) -> map_data {
-        const auto chunks = detail::parse_chunks(ckmp);
-        const auto *heightmap = detail::find(chunks, "HeightMapData");
-        const auto *blend = detail::find(chunks, "BlendTileData");
-        if (heightmap == nullptr || blend == nullptr) throw terrain_error("map has no terrain chunks");
+        try {
+            auto document = ra3::assets::map_document::parse(detail::as_bytes(ckmp));
 
-        map_data out;
-        detail::parse_heightmap(ckmp, *heightmap, out);
-        detail::parse_blend(ckmp, *blend, out);
-        if (const auto *water = detail::find(chunks, "GlobalWaterSettings"); water != nullptr && water->size >= 8U) {
-            out.has_water = detail::read_u32(ckmp.data() + water->offset) != 0U;
-            const auto bits = detail::read_u32(ckmp.data() + water->offset + 4U);
-            std::memcpy(&out.water_plane_z, &bits, sizeof(out.water_plane_z));
+            map_data out;
+            const auto height = document.height_map();
+            if (!height) throw terrain_error("map has no HeightMapData chunk");
+            out.width = height->width;
+            out.height = height->height;
+            out.border_width = height->border_width;
+            out.elevations.assign(height->elevations.begin(), height->elevations.end());
+
+            const auto *blend = document.find_chunk("BlendTileData");
+            if (blend == nullptr) throw terrain_error("map has no BlendTileData chunk");
+            detail::parse_blend(detail::as_u8(blend->payload), blend->version, out);
+
+            if (const auto *water = document.find_chunk("GlobalWaterSettings"); water != nullptr && water->payload.size() >= 8U) {
+                const auto *bytes = reinterpret_cast<const uint8 *>(water->payload.data());
+                out.has_water = detail::read_u32(bytes) != 0U;
+                const auto bits = detail::read_u32(bytes + 4U);
+                std::memcpy(&out.water_plane_z, &bits, sizeof(out.water_plane_z));
+            }
+            out.valid = true;
+            return out;
+        } catch (const ra3::assets::asset_error &error) {
+            throw terrain_error(error.what());
         }
-        out.valid = true;
-        return out;
     }
 
     /** The decoded terrain textures, parallel to `map_data::textures`. */
     struct texture_set {
         std::vector<image> images;
+        image water_flow;   ///< `ra3_deepocean.tga`: SAGE water flow/distortion (RG), optional.
+        image water_normal; ///< `ra3_deepocean_nrm.tga`: SAGE water bump normal, optional.
 
         [[nodiscard]] auto resolved() const -> usize {
             usize n = 0;
@@ -336,6 +296,10 @@ export namespace ra3::terrain {
         };
         std::vector<fs::big_archive> archives;
         std::unordered_map<std::string, source> files;
+        source flow_src{};
+        source nrm_src{};
+        bool has_flow = false;
+        bool has_nrm = false;
         for (const auto &name: {"Terrain.big", "Core11.big"}) {
             const auto path = data_dir / name;
             std::error_code ec;
@@ -344,9 +308,13 @@ export namespace ra3::terrain {
         }
         for (const auto &archive: archives) {
             for (const auto &entry: archive.entries()) {
-                auto stem = detail::tga_stem(entry.name);
-                if (stem.size() > 4U && stem.ends_with("_nrm")) continue;
                 if (!entry.name.ends_with(".tga") && !entry.name.ends_with(".TGA")) continue;
+                auto stem = detail::tga_stem(entry.name);
+                // The global ocean flow/normal pair is grabbed separately: the
+                // tile index deliberately drops `_nrm` files.
+                if (stem == "ra3_deepocean") { flow_src = source{&archive, entry.name}; has_flow = true; continue; }
+                if (stem == "ra3_deepocean_nrm") { nrm_src = source{&archive, entry.name}; has_nrm = true; continue; }
+                if (stem.size() > 4U && stem.ends_with("_nrm")) continue;
                 files.try_emplace(stem, source{&archive, entry.name});
             }
         }
@@ -378,6 +346,16 @@ export namespace ra3::terrain {
                 // Leave the slot empty; the renderer falls back to a palette.
             }
         }
+        const auto decode_water = [](const source &src, bool present) -> image {
+            if (!present) return {};
+            try {
+                return ra3::render::decode_tga(src.archive->read(src.entry, true));
+            } catch (const std::exception &) {
+                return {};
+            }
+        };
+        set.water_flow = decode_water(flow_src, has_flow);
+        set.water_normal = decode_water(nrm_src, has_nrm);
         return set;
     }
 
@@ -396,8 +374,8 @@ export namespace ra3::terrain {
     };
 
     namespace detail {
-        /** Index `*.tga` under a terrain dir by stem (lower-cased), ignoring normals. */
-        [[nodiscard]] inline auto terrain_file_index(const std::filesystem::path &dir)
+        /** Index `*.tga` under a terrain dir by stem (lower-cased). */
+        [[nodiscard]] inline auto terrain_file_index(const std::filesystem::path &dir, bool include_normals = false)
             -> std::unordered_map<std::string, std::filesystem::path> {
             std::unordered_map<std::string, std::filesystem::path> files;
             std::error_code ec;
@@ -412,7 +390,7 @@ export namespace ra3::terrain {
                 std::transform(parent.begin(), parent.end(), parent.begin(), [](unsigned char ch) { return static_cast<char>(std::tolower(ch)); });
                 if (parent != "terrain") continue;
                 auto stem = tga_stem(path.filename().string());
-                if (stem.size() > 4U && stem.ends_with("_nrm")) continue;
+                if (!include_normals && stem.size() > 4U && stem.ends_with("_nrm")) continue;
                 files.try_emplace(stem, path);
             }
             return files;
@@ -438,11 +416,16 @@ export namespace ra3::terrain {
      * Used to stage just the tiles a single map needs (e.g. the wasm preload).
      */
     [[nodiscard]] inline auto resolve_texture_files(const map_data &map, const std::filesystem::path &dir) -> std::vector<std::filesystem::path> {
-        const auto files = detail::terrain_file_index(dir);
+        // Include normals so the global ocean flow/normal pair is staged too:
+        // the terrain pass appends them to the atlas.
+        const auto files = detail::terrain_file_index(dir, true);
         std::vector<std::filesystem::path> resolved;
         for (const auto &texture: map.textures) {
             if (auto found = detail::match_terrain_file(files, texture.name); !found.empty()) resolved.push_back(std::move(found));
         }
+        for (const auto *water: {"ra3_deepocean", "ra3_deepocean_nrm"}) {
+            if (const auto it = files.find(water); it != files.end()) resolved.push_back(it->second);
+        }
         std::sort(resolved.begin(), resolved.end());
         resolved.erase(std::unique(resolved.begin(), resolved.end()), resolved.end());
         return resolved;
@@ -451,21 +434,26 @@ export namespace ra3::terrain {
     /** Load tile textures from a directory of loose `*.tga` files (extracted assets). */
     [[nodiscard]] inline auto load_textures_from_dir(const map_data &map, const std::filesystem::path &dir,
                                                     const std::function<void(float)> &progress = {}) -> texture_set {
-        const auto files = detail::terrain_file_index(dir);
+        const auto files = detail::terrain_file_index(dir, true);
         texture_set set;
         set.images.resize(map.textures.size());
+        const auto decode_file = [](const std::filesystem::path &path) -> image {
+            if (path.empty()) return {};
+            try {
+                std::ifstream in(path, std::ios::binary);
+                std::vector<uint8> raw((std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>());
+                return ra3::render::decode_tga(raw);
+            } catch (const std::exception &) {
+                return {};
+            }
+        };
         for (usize i = 0; i < map.textures.size(); ++i) {
             const auto found = detail::match_terrain_file(files, map.textures[i].name);
-            if (!found.empty()) {
-                try {
-                    std::ifstream in(found, std::ios::binary);
-                    std::vector<uint8> raw((std::istreambuf_iterator<char>(in)), std::istreambuf_iterator<char>());
-                    set.images[i] = ra3::render::decode_tga(raw);
-                } catch (const std::exception &) {
-                }
-            }
+            set.images[i] = decode_file(found);
             if (progress && !map.textures.empty()) progress(static_cast<float>(i + 1U) / static_cast<float>(map.textures.size()));
         }
+        if (const auto it = files.find("ra3_deepocean"); it != files.end()) set.water_flow = decode_file(it->second);
+        if (const auto it = files.find("ra3_deepocean_nrm"); it != files.end()) set.water_normal = decode_file(it->second);
         return set;
     }
 
@@ -539,7 +527,12 @@ export namespace ra3::terrain {
             out.cell_data[i * 4U + 3U] = static_cast<uint16>(packed);
         }
 
-        out.layer_count = static_cast<uint32>(std::max<usize>(1U, map.textures.size()));
+        // Two extra atlas layers hold the SAGE water flow map and bump normal so
+        // the water shader can sample them without a new binding on any backend:
+        // they are always the last two layers (water_flow = layer_count - 2,
+        // water_normal = layer_count - 1).
+        const auto tile_layers = static_cast<uint32>(std::max<usize>(1U, map.textures.size()));
+        out.layer_count = tile_layers + 2U;
         uint32 layer_size = 64U;
         for (const auto &img: set.images) {
             if (!img.empty()) layer_size = std::max(layer_size, img.width());
@@ -554,17 +547,26 @@ export namespace ra3::terrain {
         }
 
         out.layers.assign(static_cast<usize>(out.layer_count) * layer_size * layer_size, 0xFF3A4550U);
-        for (usize i = 0; i < map.textures.size(); ++i) {
-            const auto &img = set.images[i];
-            if (img.empty()) continue;
+        // Copy `img` into atlas layer `index`, box-nearest downscaled to
+        // `layer_size`; `fallback` is the ARGB used when the image is absent.
+        const auto blit_layer = [&](uint32 index, const image &img, uint32 fallback) {
             for (uint32 y = 0; y < layer_size; ++y) {
-                const auto sy = std::min(img.height() - 1U, y * img.height() / layer_size);
                 for (uint32 x = 0; x < layer_size; ++x) {
-                    const auto sx = std::min(img.width() - 1U, x * img.width() / layer_size);
-                    out.layers[(i * layer_size + y) * layer_size + x] = img.data()[static_cast<usize>(sy) * img.width() + sx];
+                    uint32 px = fallback;
+                    if (!img.empty()) {
+                        const auto sy = std::min(img.height() - 1U, y * img.height() / layer_size);
+                        const auto sx = std::min(img.width() - 1U, x * img.width() / layer_size);
+                        px = img.data()[static_cast<usize>(sy) * img.width() + sx];
+                    }
+                    out.layers[(static_cast<usize>(index) * layer_size + y) * layer_size + x] = px;
                 }
             }
+        };
+        for (usize i = 0; i < map.textures.size(); ++i) {
+            blit_layer(static_cast<uint32>(i), set.images[i], 0xFF3A4550U);
         }
+        blit_layer(tile_layers, set.water_flow, 0xFF808080U);     // neutral flow  (0, 0)
+        blit_layer(tile_layers + 1U, set.water_normal, 0xFF8080FFU); // flat normal (0, 0, 1)
         if (progress) progress(1.0F);
         return out;
     }
@@ -1138,49 +1140,70 @@ export namespace ra3::terrain {
                     continue;
                 }
 
-                auto t = cell_size * 0.5F;
-                auto dt = cell_size * 0.5F;
+                // Clip the ray to the map's XY rectangle. The boundary is an
+                // exact plane, so the silhouette there stays razor-sharp
+                // instead of stair-stepping across it; outside the map is sky.
+                auto t_enter = 0.0F;
+                auto t_exit = 1.0e30F;
+                const auto slab = [](float origin, float dir, float span, float &lo_t, float &hi_t) -> bool {
+                    if (std::abs(dir) < 1.0e-6F) return origin >= 0.0F && origin <= span;
+                    const auto a = (0.0F - origin) / dir;
+                    const auto b = (span - origin) / dir;
+                    lo_t = std::max(lo_t, std::min(a, b));
+                    hi_t = std::min(hi_t, std::max(a, b));
+                    return true;
+                };
+                if (!slab(cam_x, dx, world_w, t_enter, t_exit) || !slab(cam_y, dy, world_h, t_enter, t_exit) || t_exit <= 0.0F) {
+                    hi.data()[pixel] = argb(150, 170, 200);
+                    continue;
+                }
+
+                const auto surface_at = [&](float wx, float wy) -> float {
+                    const auto h = sample_height(wx, wy);
+                    return map.has_water ? std::max(h, static_cast<float>(map.water_plane_z)) : h;
+                };
+
+                // March the heightfield cell by cell: the step is never longer
+                // than the time to cross one cell (in the dominant horizontal
+                // axis), while a clearance term lets the ray skip the empty air
+                // above the surface. Resolving every cell is what keeps cliff and
+                // map-edge silhouettes from quantising into huge stair-steps that
+                // crawl/wave as the camera pans.
+                const auto horiz = std::max(std::abs(dx), std::abs(dy));
+                const auto cell_step = std::min(cell_size / std::max(horiz, 1.0e-4F), cell_size * 32.0F);
+                auto t = std::max(t_enter, cell_size * 0.5F);
                 auto prev_t = t;
                 bool hit = false;
                 float hit_t = 0.0F;
-                for (int iter = 0; iter < 4000 && t < 60000.0F; ++iter) {
+                for (int iter = 0; iter < 4096 && t <= t_exit; ++iter) {
                     const auto wx = cam_x + dx * t;
                     const auto wy = cam_y + dy * t;
                     const auto wz = cam_z + dz * t;
-                    if (wx < 0.0F || wy < 0.0F || wx >= world_w || wy >= world_h) {
-                        prev_t = t;
-                        dt *= 1.03F;
-                        t += dt;
-                        continue;
-                    }
-                    if (map.has_water && wz <= map.water_plane_z) {
-                        hit = true;
-                        hit_t = t;
-                        break;
-                    }
-                    if (wz <= sample_height(wx, wy)) {
+                    const auto surface = surface_at(wx, wy);
+                    if (wz <= surface) {
                         hit = true;
                         hit_t = t;
                         break;
                     }
+                    const auto clearance = (wz - surface) / std::max(-dz, 1.0e-4F);
                     prev_t = t;
-                    dt *= 1.03F;
-                    t += dt;
+                    t += std::clamp(clearance, cell_step, cell_step * 8.0F);
                 }
                 if (!hit) {
                     hi.data()[pixel] = argb(150, 170, 200);
                     continue;
                 }
 
+                // Refine the first crossing; with a sub-cell bracket this
+                // converges to the exact surface point.
                 auto lo = prev_t;
                 auto up = hit_t;
-                for (int i = 0; i < 6; ++i) {
+                for (int i = 0; i < 18; ++i) {
                     const auto mid = 0.5F * (lo + up);
                     const auto wx = cam_x + dx * mid;
                     const auto wy = cam_y + dy * mid;
                     const auto wz = cam_z + dz * mid;
-                    const auto water = map.has_water && wz <= map.water_plane_z;
-                    if (water || wz <= sample_height(wx, wy)) {
+                    if (wz <= surface_at(wx, wy)) {
                         up = mid;
                     } else {
                         lo = mid;

tests/ra3_tests.cpp

@@ -1,5 +1,6 @@
 import std;
 import ra3;
+import ra3.assets;
 
 namespace {
     int failures = 0;
@@ -193,6 +194,12 @@ auto main() -> int {
     }
     check(!space_lit, "a space paints nothing");
 
+    // FPS label: the active backend name is appended (e.g. `[vulkan]`).
+    const auto fps_label = render::compose_fps_label(155U, 0, "vulkan");
+    const auto fps_plain = render::compose_fps_label(155U, 0);
+    check(fps_label.width() > fps_plain.width(), "FPS label grows when the backend is shown");
+    check(fps_label.width() == render::text_width("FPS: 155/vsync [vulkan]") + 8U, "FPS label includes the backend name");
+
     const auto box = render::fit_rect(1280.0F, 720.0F, 1920.0F, 1080.0F);
     check(box.x == 0.0F && box.y == 0.0F && box.w == 1920.0F && box.h == 1080.0F, "fit_rect fills a same-aspect window");
 
@@ -300,6 +307,100 @@ auto main() -> int {
 
     check(models::decode_dds(std::vector<core::uint8>{1U, 2U, 3U}).empty(), "a non-DDS payload yields no image");
 
+    // Real-asset checks (opt-in): set OPENRA3_TEST_ASSETS to an extracted assets
+    // directory. They run the libra3assets-backed readers over the retail data and
+    // compare the map names against the golden `maps/map_names.tsv` written by the
+    // previous hand-rolled parser.
+    if (const char *assets_env = std::getenv("OPENRA3_TEST_ASSETS"); assets_env != nullptr && *assets_env != '\0') {
+        const std::filesystem::path assets{assets_env};
+        const auto read_all = [](const std::filesystem::path &path) {
+            std::ifstream in(path, std::ios::binary);
+            return std::vector<core::uint8>{std::istreambuf_iterator<char>(in), std::istreambuf_iterator<char>()};
+        };
+
+        const auto golden = assets / "maps" / "map_names.tsv";
+        // The golden table came from the newest `Lang-English<N>.big`; mirror that.
+        const auto pick_english_csf = [](const std::filesystem::path &raw) -> std::filesystem::path {
+            std::filesystem::path best;
+            int best_version = -1;
+            std::error_code ec;
+            for (const auto &entry: std::filesystem::directory_iterator(raw, ec)) {
+                if (!entry.is_directory()) continue;
+                const auto name = entry.path().filename().string();
+                if (name.rfind("Lang-English", 0) != 0) continue;
+                int version = 0;
+                try {
+                    version = std::stoi(name.substr(12));
+                } catch (const std::exception &) {
+                    continue;
+                }
+                if (version > best_version) {
+                    best_version = version;
+                    best = entry.path() / "data" / "gamestrings.csf";
+                }
+            }
+            if (!best.empty() && std::filesystem::exists(best)) return best;
+            return raw / "English" / "data" / "gamestrings.csf";
+        };
+        const auto csf_path = pick_english_csf(assets / "raw");
+        if (std::filesystem::exists(golden) && std::filesystem::exists(csf_path)) {
+            const auto table = map::parse_map_names(read_all(csf_path));
+            std::ifstream in(golden, std::ios::binary);
+            std::string line;
+            std::size_t matched = 0;
+            std::size_t mismatched = 0;
+            while (std::getline(in, line)) {
+                const auto tab = line.find('\t');
+                if (tab == std::string::npos) continue;
+                const auto id = line.substr(0, tab);
+                const auto expected = line.substr(tab + 1U);
+                if (table.lookup(id) == expected) {
+                    ++matched;
+                } else {
+                    ++mismatched;
+                    if (mismatched <= 5U) std::printf("  name mismatch %s: golden '%s' new '%s'\n", id.c_str(), expected.c_str(), table.lookup(id).c_str());
+                }
+            }
+            std::printf("  real CSF: %zu names, golden %zu matched, %zu mismatched\n", table.names.size(), matched, mismatched);
+            check(mismatched == 0U, "map names reproduce the golden map_names.tsv");
+        }
+
+        std::size_t maps_ok = 0;
+        std::size_t maps_bad = 0;
+        std::size_t library_starts = 0;
+        std::size_t no_starts = 0;
+        std::size_t roundtrip_bad = 0;
+        const auto to_bytes = [](std::span<const core::uint8> data) {
+            return std::span<const std::byte>{reinterpret_cast<const std::byte *>(data.data()), data.size()};
+        };
+        for (const auto &entry: std::filesystem::directory_iterator(assets / "maps")) {
+            if (!entry.is_regular_file() || entry.path().extension() != ".map") continue;
+            try {
+                const auto ckmp = map::to_ckmp(read_all(entry.path()));
+                const auto parsed = terrain::parse_map(ckmp);
+                const auto starts = map::starts_from_ckmp(ckmp);
+                const auto document = ra3::assets::map_document::parse(to_bytes(ckmp));
+                if (document.player_starts().size() >= 2U) ++library_starts; else ++no_starts;
+                if (!std::ranges::equal(document.to_ckmp(), to_bytes(ckmp))) ++roundtrip_bad;
+                if (parsed.width > 0U && parsed.height > 0U && parsed.elevations.size() == static_cast<std::size_t>(parsed.width) * parsed.height && starts.size() >= 2U) {
+                    ++maps_ok;
+                } else {
+                    ++maps_bad;
+                    if (maps_bad <= 5U)
+                        std::printf("  map oddity %s: %ux%u starts %zu\n", entry.path().filename().string().c_str(), parsed.width, parsed.height, starts.size());
+                }
+            } catch (const std::exception &error) {
+                ++maps_bad;
+                if (maps_bad <= 5U) std::printf("  map FAIL %s: %s\n", entry.path().filename().string().c_str(), error.what());
+            }
+        }
+        std::printf("  real maps: %zu ok, %zu bad; player_starts resolved %zu, unresolved %zu; round-trip mismatched %zu\n", maps_ok, maps_bad, library_starts,
+                    no_starts, roundtrip_bad);
+        check(maps_bad == 0U, "every extracted map parses terrain + starts through libra3assets");
+        check(no_starts == 0U, "libra3assets player_starts() resolves every retail map's start waypoints");
+        check(roundtrip_bad == 0U, "libra3assets re-serialises every retail map byte-for-byte");
+    }
+
     if (failures == 0) {
         std::puts("ra3_tests: OK");
     }

third_party/libenderlog/README.md

@@ -131,13 +131,13 @@ and `log::set_sinks({...})` replaces them.
 ```cpp
 namespace log = ender::log;
 
-// Archive any existing enderlog.log to enderlog.log.<timestamp>, then start a
+// Archive any existing enderlog.log to enderlog.<timestamp>.log, then start a
 // fresh file for this run. Rotate at 64 KiB and keep the last 5 archives.
 auto sink = log::add_file_sink("enderlog.log", {.max_file_size = 64 * 1024, .max_archives = 5});
 ```
 
 - **No appending onto a previous run.** On open, an existing non-empty
-  `enderlog.log` is renamed to `enderlog.log.<YYYYmmdd-HHMMSS>` before the new
+  `enderlog.log` is renamed to `enderlog.<YYYYmmdd-HHMMSS>.log` before the new
   file is created, so every run gets its own file and the previous run's log is
   preserved. A leftover empty file is simply replaced.
 - `file_options::max_file_size` (0 disables) rotates the active file mid-run the

third_party/libenderlog/src/ender.log.cppm

@@ -182,7 +182,8 @@ export namespace ender::log {
      * `path` is the active file. When the sink opens it and the file already
      * holds data, that file is renamed to a timestamped archive first, so a run
      * never appends onto a previous run's log: every start begins a fresh file
-     * and the old one is preserved as `<path>.<YYYYmmdd-HHMMSS>`. The same
+     * and the old one is preserved with the timestamp before its extension, as
+     * `<stem>.<YYYYmmdd-HHMMSS>.log`. The same
      * happens mid-run once the active file passes `file_options::max_file_size`.
      * `file_options::max_archives` bounds how many archives are kept.
      *
@@ -238,13 +239,21 @@ export namespace ender::log {
             if (stream_.is_open()) stream_.close();
             const auto stamp = std::format("{:%Y%m%d-%H%M%S}",
                                            std::chrono::floor<std::chrono::seconds>(std::chrono::system_clock::now()));
-            auto archive = path_;
-            archive += "." + stamp;
+            // Keep the original extension last, with the timestamp in the
+            // middle: `<stem>.<stamp>[.<n>]<ext>`.
+            const auto name = [&](const std::size_t counter) {
+                auto candidate = path_.parent_path() / path_.stem();
+                candidate += ".";
+                candidate += stamp;
+                if (counter > 0) candidate += std::format(".{}", counter);
+                candidate += path_.extension();
+                return candidate;
+            };
+            auto archive = name(0);
             // Two rotations can land in the same second; disambiguate with a
             // counter rather than overwrite the earlier archive.
             for (auto counter = 1; std::filesystem::exists(archive); ++counter) {
-                archive = path_;
-                archive += std::format(".{}.{}", stamp, counter);
+                archive = name(counter);
             }
             std::filesystem::rename(path_, archive);
             archives_.push_back(archive);

third_party/libra3assets/README.md

@@ -0,0 +1,134 @@
+# libra3assets
+
+A dependency-free C++26 library that reads **and writes** the resource files
+Red Alert 3 ships, so tooling (map editors in particular) can work with the
+retail assets directly. No engine, no game install required to build - only to
+feed it data.
+
+It is a sub-project of this repository, a sibling of
+[`libra3replay`](../libra3replay/README.md), and follows the same build
+conventions (C++26 modules, `import std;`, GCC 16, CMake 4 + Ninja).
+
+## What it handles
+
+| Module             | Format                                                              | Read | Write |
+| ------------------ | ------------------------------------------------------------------- | :--: | :---: |
+| `ra3.assets:big`      | `BIG4` archives (`Data\*.big`)                                   | yes  | yes   |
+| `ra3.assets:refpack`  | EA RefPack codec (`10 FB`)                                       | yes  | yes   |
+| `ra3.assets:binary`   | compiled `BinaryAsset` streams (`.bin` + `.manifest`, `cdata`)   | yes  | -     |
+| `ra3.assets:csf`      | SAGE `.csf` string tables (`gamestrings.csf`)                    | yes  | yes   |
+| `ra3.assets:map`      | SAGE `.map` containers (`CkMp`) incl. `HeightMapData`/objects    | yes  | yes   |
+| `ra3.assets:bytes`    | bounds-checked little-/big-endian readers and writers            | yes  | yes   |
+
+The **map** module is the centrepiece for a map editor. A `.map` is modelled as
+an ordered list of named, versioned `CkMp` chunks; chunks the library does not
+type (e.g. `BlendTileData`, `SidesList`) are preserved byte-for-byte and the
+asset-name table keeps its original indices, so an edit/ serialise cycle is
+lossless. Typed accessors cover the terrain grid (`HeightMapData`), every placed
+object (`ObjectsList`, including the `*Waypoints/Waypoint` objects that carry
+`Player_N_Start`), `MPPositionList`, `WorldInfo` and `WaypointsList`.
+
+The **binary** module parses the compiled `BinaryAsset` streams that
+BinaryAssetBuilder produces (`data\static.bin`, `data\global.bin`, ...): the
+manifest index, each asset's instance slice, its relocation/import sidecars and
+its `cdata` blob, plus the hash used to name assets.
+
+## Build
+
+```bash
+cmake -S libra3assets -B build -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=g++-16
+cmake --build build
+ctest --test-dir build --output-on-failure
+```
+
+The library is a set of C++20/26 modules (`ra3.assets` plus the `:error`,
+`:bytes`, `:refpack`, `:big`, `:binary`, `:csf` and `:map` partitions) that
+imports the standard library (`import std;`). That needs **CMake 4.0+ with the
+Ninja generator** and a compiler whose standard library ships a `std` module -
+**GCC 16** in practice. The tests need nothing but the library itself.
+
+> Building with the distro GCC 16: pass `-DCMAKE_CXX_COMPILER=g++-16`.
+
+## Use
+
+```cpp
+import std;
+import ra3.assets;
+
+using namespace ra3::assets;
+
+// --- a map, for a map editor -------------------------------------------------
+auto document = map_document::open("map_mp_2_black1b.map");
+
+if (const auto height = document.height_map()) {
+    std::println("terrain {}x{}", height->width, height->height);
+    auto grid = *height;                       // copy, then edit
+    grid.set(10, 10, grid.at(10, 10) + 1);     // raise a cell
+    document.set_height_map(std::move(grid));  // re-encode the chunk
+}
+
+for (const auto &start: document.player_starts())
+    std::println("Player {} at ({}, {})", start.index, start.position.x, start.position.y);
+
+for (const auto &object: document.objects())
+    if (object.type_name == "*Waypoints/Waypoint")
+        std::println("{} -> {}", object.property("waypointName")->as_ascii(), object.position.y);
+
+// Lossless: unknown chunks and the name table survive the round-trip.
+write_file("edited.map", document.serialize(/* compress = */ true));
+
+// --- a BIG4 archive ----------------------------------------------------------
+const auto archive = big_archive::open("Data/GlobalStream.big");
+std::println("{} entries", archive.size());
+for (const auto *entry: archive.find("audio"))
+    std::println("{} ({} bytes)", entry->name, entry->size);
+
+// --- a compiled BinaryAsset stream ------------------------------------------
+const auto stream = binary_stream_from_big(archive, binary_stream::global, /* need_data = */ false);
+for (const auto &[type, count]: stream.type_counts())
+    std::println("{:6}  {}", count, type);
+```
+
+The API deliberately avoids integer IDs for anything selectable: chunk kinds are
+`chunk_kind` (e.g. `chunk_kind::height_map_data`), streams are `binary_stream`
+(`binary_stream::global`), property types are `property_type`, and an
+`asset_property` carries a `std::variant<bool, std::int32_t, float, std::string,
+std::u16string>`.
+
+## Command-line tool
+
+`ra3assets-cli` is built alongside the library:
+
+```
+ra3assets-cli big    list    <archive.big> [match]
+ra3assets-cli big    extract <archive.big> <out-dir> [match]
+ra3assets-cli binary list    <path> [type]
+ra3assets-cli binary types   <path> [static|global|locale|static_l|static_m]
+ra3assets-cli binary cat     <path> <Type:Instance|#index> <out-file>
+ra3assets-cli map    info    <map-file>
+ra3assets-cli map    starts  <map-file>
+ra3assets-cli map    repack  <map-file> <out-file> [--compress]
+ra3assets-cli csf    <csf-or-game-dir-or-big> [label]
+ra3assets-cli hash   <text>...
+```
+
+## Notes and limits
+
+- A `BIG4` archive opened from disk keeps only its index in memory and reads
+  payloads on demand, so enumerating the ~700 MB retail `StaticStream.big` costs
+  a few megabytes; pass `need_data = false` to `binary_stream_from_big` when you
+  only need the manifest. A parsed `.map` document is held in full - that is what
+  its typed accessors edit.
+- `set_height_map` keeps the on-disk `HeightMapData` version (RA3 uses 6, i.e.
+  16-bit elevations). Older 8-bit maps serialise back as 8-bit.
+- RefPack compression is a plain greedy LZ77 matcher. It is lossless against the
+  bundled decoder and produces streams the game's decoder accepts, but it is
+  slightly less dense than the retail compressor (≈3% on a typical map).
+- `BlendTileData` (terrain texture blending) is preserved but not yet
+  type-modelled; a map editor should treat the chunk as opaque for now. The
+  planned follow-up covers `BlendTileData` and `SidesList`.
+- Only `BIG4` is supported (RA3's format); older `BIGF` archives are not.
+
+The on-disk layouts were reverse engineered from the shipped files and
+cross-checked against [`ra3tools`](../ra3tools/), OpenRA3's `ra3.fs`/`ra3.map`
+modules and the OpenSAGE re-implementation (`reference/OpenSAGE`).

third_party/libra3assets/src/assets.cppm

@@ -0,0 +1,65 @@
+/**
+ * libra3assets - read (and write) Red Alert 3's built-in resource files.
+ *
+ * The primary module interface re-exports every partition:
+ *
+ * - `:error`   - the `asset_error` exception family
+ * - `:bytes`   - bounds-checked little-/big-endian readers and writers
+ * - `:refpack` - EA's RefPack codec (decompress and compress)
+ * - `:big`     - `BIG4` archives (`Data\*.big`), read and write
+ * - `:binary`  - compiled `BinaryAsset` streams (`*.bin` + `.manifest`)
+ * - `:csf`     - SAGE `.csf` string tables
+ * - `:map`     - SAGE `.map` containers (`CkMp`), read and write
+ *
+ * Nothing here reads game data on its own: callers point the library at their
+ * own installation (`RA3_GAME_DIR` / `C:\Red Alert 3`).
+ */
+export module ra3.assets;
+
+export import :error;
+export import :bytes;
+export import :refpack;
+export import :big;
+export import :binary;
+export import :csf;
+export import :map;
+
+import std;
+
+export namespace ra3::assets {
+
+    /**
+     * Locate a Red Alert 3 installation.
+     *
+     * Resolution order: the explicit argument, then `$RA3_GAME_DIR`, then the
+     * default `C:\Red Alert 3`. A directory qualifies only if it has a `Data`
+     * subdirectory.
+     */
+    [[nodiscard]] inline auto find_game_dir(const std::optional<std::filesystem::path> &explicit_dir = std::nullopt) -> std::optional<std::filesystem::path> {
+        const auto qualifies = [](const std::filesystem::path &candidate) {
+            std::error_code ec;
+            return !candidate.empty() && std::filesystem::is_directory(candidate / "Data", ec);
+        };
+
+        if (explicit_dir && qualifies(*explicit_dir)) return explicit_dir;
+        if (const auto *env = std::getenv("RA3_GAME_DIR"); env != nullptr && *env != '\0') {
+            const std::filesystem::path candidate{env};
+            if (qualifies(candidate)) return candidate;
+        }
+        const std::filesystem::path default_dir{"C:/Red Alert 3"};
+        if (qualifies(default_dir)) return default_dir;
+        return std::nullopt;
+    }
+
+    /** Every `Data\*.big` archive in an installation, sorted by name. */
+    [[nodiscard]] inline auto list_archives(const std::filesystem::path &game_dir) -> std::vector<std::filesystem::path> {
+        std::vector<std::filesystem::path> archives;
+        std::error_code ec;
+        for (const auto &entry: std::filesystem::directory_iterator(game_dir / "Data", ec)) {
+            if (entry.is_regular_file() && entry.path().extension() == ".big") archives.push_back(entry.path());
+        }
+        std::ranges::sort(archives);
+        return archives;
+    }
+
+} // namespace ra3::assets

third_party/libra3assets/src/big.cppm

@@ -0,0 +1,274 @@
+/**
+ * `BIG4` archives - Red Alert 3's on-disk asset container.
+ *
+ * Retail RA3 ships its data as `Data\*.big`: a 16-byte header, a variable-
+ * length entry index and the 64-byte-aligned payloads. The count and the entry
+ * offsets/sizes are **big-endian** (the header size is little-endian, matching
+ * the retail files); each payload may itself be RefPack-compressed, which is
+ * detected from its own magic rather than flagged in the index.
+ *
+ * Both directions are implemented so a map editor can repack an archive.
+ */
+export module ra3.assets:big;
+
+import std;
+
+import :bytes;
+import :error;
+import :refpack;
+
+export namespace ra3::assets {
+
+    /** One file inside a `BIG4` archive. */
+    struct big_entry {
+        std::string name;
+        std::uint32_t offset = 0;
+        std::uint32_t size = 0;
+    };
+
+    namespace detail {
+        [[nodiscard]] inline auto align_up(std::uint64_t value, std::uint64_t alignment) -> std::uint64_t {
+            return (value + alignment - 1U) / alignment * alignment;
+        }
+
+        [[nodiscard]] inline constexpr auto bswap32(std::uint32_t value) -> std::uint32_t {
+            return ((value & 0x000000FFU) << 24U) | ((value & 0x0000FF00U) << 8U) | ((value & 0x00FF0000U) >> 8U) | ((value & 0xFF000000U) >> 24U);
+        }
+    }
+
+    /**
+     * A parsed `BIG4` archive.
+     *
+     * Opening from disk parses only the index; payloads are read (and
+     * RefPack-decompressed) on demand, so a multi-hundred-megabyte archive costs
+     * a few megabytes to enumerate. An archive built from an in-memory image
+     * (`from_bytes`) slices its payloads out of that buffer instead.
+     */
+    class big_archive {
+    public:
+        /** Read and parse an archive from disk, keeping only the index in memory. */
+        [[nodiscard]] static auto open(const std::filesystem::path &path) -> big_archive {
+            big_archive archive;
+            archive.path_ = path;
+
+            std::error_code ec;
+            archive.file_size_ = static_cast<std::uint64_t>(std::filesystem::file_size(path, ec));
+            if (ec) throw big_error("cannot stat archive: " + path.string());
+
+            std::ifstream in(path, std::ios::binary);
+            if (!in) throw big_error("cannot open archive: " + path.string());
+
+            std::array<std::byte, 16> header{};
+            in.read(reinterpret_cast<char *>(header.data()), static_cast<std::streamsize>(header.size()));
+            if (!in || std::string_view{reinterpret_cast<const char *>(header.data()), 4} != "BIG4") throw big_error("not a BIG4 archive: " + path.string());
+
+            // The index is a dense variable-length table from offset 16; read a
+            // window and grow it until every entry parses. Payloads are never
+            // touched, so the memory cost stays at the index size.
+            const auto size = archive.file_size_;
+            std::uint64_t window = std::min<std::uint64_t>(size, 1U << 20U);
+            std::vector<std::byte> buffer;
+            for (;;) {
+                buffer.resize(static_cast<std::size_t>(window));
+                in.clear();
+                in.seekg(0);
+                in.read(reinterpret_cast<char *>(buffer.data()), static_cast<std::streamsize>(window));
+                const auto got = in.gcount();
+                buffer.resize(got > 0 ? static_cast<std::size_t>(got) : 0U);
+
+                std::vector<big_entry> entries;
+                if (big_archive::parse_index(buffer, entries)) {
+                    archive.entries_ = std::move(entries);
+                    break;
+                }
+                if (window >= size) throw big_error("truncated BIG4 index: " + path.string());
+                window = std::min<std::uint64_t>(size, window * 2U);
+            }
+            archive.reindex();
+            return archive;
+        }
+
+        /** Parse an in-memory archive image; payloads are sliced from it. */
+        [[nodiscard]] static auto from_bytes(std::vector<std::byte> bytes) -> big_archive {
+            big_archive archive;
+            archive.bytes_ = std::move(bytes);
+            archive.in_memory_ = true;
+            if (!big_archive::parse_index(archive.bytes_, archive.entries_)) throw big_error("not a BIG4 archive");
+            archive.reindex();
+            return archive;
+        }
+
+        [[nodiscard]] auto path() const -> const std::filesystem::path & { return this->path_; }
+        [[nodiscard]] auto entries() const -> const std::vector<big_entry> & { return this->entries_; }
+        [[nodiscard]] auto size() const -> std::size_t { return this->entries_.size(); }
+        [[nodiscard]] auto contains(std::string_view name) const -> bool { return this->index_.contains(std::string{name}); }
+
+        /** The entry with exactly this name, or `nullptr`. */
+        [[nodiscard]] auto find_exact(std::string_view name) const -> const big_entry * {
+            const auto it = this->index_.find(std::string{name});
+            return it == this->index_.end() ? nullptr : &this->entries_[it->second];
+        }
+
+        /** Every entry whose name contains `needle`, in index order. */
+        [[nodiscard]] auto find(std::string_view needle) const -> std::vector<const big_entry *> {
+            std::vector<const big_entry *> matches;
+            for (const auto &entry: this->entries_) {
+                if (entry.name.find(needle) != std::string::npos) matches.push_back(&entry);
+            }
+            return matches;
+        }
+
+        /** Read an entry's payload; RefPack-decompress it when `decompress`. */
+        [[nodiscard]] auto read(std::string_view name, bool decompress = true) const -> std::vector<std::byte> {
+            const auto *entry = this->find_exact(name);
+            if (entry == nullptr) throw big_error("no such entry: " + std::string{name});
+            return this->read(*entry, decompress);
+        }
+
+        [[nodiscard]] auto read(const big_entry &entry, bool decompress = true) const -> std::vector<std::byte> {
+            const auto raw = this->stored(entry.offset, entry.size);
+            return decompress ? maybe_decompress(raw) : raw;
+        }
+
+        /** The first `count` stored bytes of an entry (no decompression). */
+        [[nodiscard]] auto read_prefix(std::string_view name, std::size_t count) const -> std::vector<std::byte> {
+            const auto *entry = this->find_exact(name);
+            if (entry == nullptr) throw big_error("no such entry: " + std::string{name});
+            return this->stored(entry->offset, static_cast<std::uint32_t>(std::min<std::size_t>(count, entry->size)));
+        }
+
+    private:
+        big_archive() = default;
+
+        /** Parse a `BIG4` index from `data`; false when it is not fully present. */
+        [[nodiscard]] static auto parse_index(std::span<const std::byte> data, std::vector<big_entry> &out) -> bool {
+            if (data.size() < 16U) return false;
+            byte_reader reader{data};
+            if (reader.read_ascii(4) != "BIG4") return false;
+            (void) reader.read_u32();    // total file size (little-endian); implied by the buffer
+            const auto count = reader.read_be_u32();
+            (void) reader.read_be_u32(); // index size
+            // Each entry is at least `u32 offset + u32 size + NUL name` (9 bytes),
+            // so a count that cannot fit bounds both the reserve and the window.
+            if (count > (data.size() - 16U) / 9U) return false;
+            out.clear();
+            out.reserve(count);
+            for (std::uint32_t i = 0; i < count; ++i) {
+                if (reader.remaining() < 8U) return false;
+                big_entry entry;
+                entry.offset = reader.read_be_u32();
+                entry.size = reader.read_be_u32();
+                // The NUL-terminated name may run past the current window.
+                std::string name;
+                bool terminated = false;
+                while (reader.remaining() > 0U) {
+                    const auto ch = reader.read_u8();
+                    if (ch == 0U) {
+                        terminated = true;
+                        break;
+                    }
+                    name.push_back(static_cast<char>(ch));
+                }
+                if (!terminated) return false;
+                entry.name = std::move(name);
+                out.push_back(std::move(entry));
+            }
+            return true;
+        }
+
+        /** Read `count` stored bytes at `offset`, from memory or from disk. */
+        [[nodiscard]] auto stored(std::uint32_t offset, std::uint32_t count) const -> std::vector<std::byte> {
+            if (this->in_memory_) {
+                if (static_cast<std::uint64_t>(offset) + count > this->bytes_.size()) throw big_error("entry extends past end of archive");
+                const auto *begin = this->bytes_.data() + offset;
+                return std::vector<std::byte>{begin, begin + count};
+            }
+            if (static_cast<std::uint64_t>(offset) + count > this->file_size_) throw big_error("entry extends past end of archive");
+            std::ifstream in(this->path_, std::ios::binary);
+            if (!in) throw big_error("cannot open archive: " + this->path_.string());
+            in.seekg(static_cast<std::streamoff>(offset));
+            std::vector<std::byte> raw(count);
+            if (count > 0U) in.read(reinterpret_cast<char *>(raw.data()), static_cast<std::streamsize>(count));
+            if (!in) throw big_error("short read from archive: " + this->path_.string());
+            return raw;
+        }
+
+        auto reindex() -> void {
+            this->index_.clear();
+            for (std::size_t i = 0; i < this->entries_.size(); ++i) this->index_.emplace(this->entries_[i].name, i);
+        }
+
+        std::filesystem::path path_;
+        std::vector<std::byte> bytes_; ///< In-memory image (from_bytes); empty when opened from disk.
+        bool in_memory_ = false;
+        std::uint64_t file_size_ = 0;
+        std::vector<big_entry> entries_;
+        std::unordered_map<std::string, std::size_t> index_;
+    };
+
+    /**
+     * Builds a `BIG4` archive.
+     *
+     * Entry payloads are written 64-byte aligned (as the retail archives are),
+     * and the header's index size reproduces the retail convention
+     * (`last-entry end + 8`). `add(..., compress = true)` RefPack-encodes the
+     * payload when that is smaller, otherwise stores it verbatim.
+     */
+    class big_writer {
+    public:
+        auto add(std::string name, std::vector<std::byte> payload, bool compress = false) -> void {
+            if (compress) {
+                auto packed = refpack_compress(payload);
+                if (packed.size() < payload.size()) payload = std::move(packed);
+            }
+            this->items_.push_back({std::move(name), std::move(payload)});
+        }
+
+        /** Serialise the archive into a fresh byte image. */
+        [[nodiscard]] auto write() const -> std::vector<std::byte> {
+            std::uint64_t table_end = 16U;
+            for (const auto &item: this->items_) table_end += 8U + item.name.size() + 1U;
+            const auto index_size = table_end + 8U;
+            const auto data_start = detail::align_up(index_size, 64U);
+
+            std::vector<std::uint64_t> offsets;
+            offsets.reserve(this->items_.size());
+            std::uint64_t cursor = data_start;
+            for (const auto &item: this->items_) {
+                offsets.push_back(cursor);
+                cursor = detail::align_up(cursor + item.payload.size(), 64U);
+            }
+
+            byte_writer writer;
+            writer.write_ascii("BIG4");
+            writer.write_u32(static_cast<std::uint32_t>(cursor)); // total file size (little-endian)
+            writer.write_u32(detail::bswap32(static_cast<std::uint32_t>(this->items_.size())));
+            writer.write_u32(detail::bswap32(static_cast<std::uint32_t>(index_size)));
+            for (std::size_t i = 0; i < this->items_.size(); ++i) {
+                writer.write_u32(detail::bswap32(static_cast<std::uint32_t>(offsets[i])));
+                writer.write_u32(detail::bswap32(static_cast<std::uint32_t>(this->items_[i].payload.size())));
+                writer.write_ascii(this->items_[i].name);
+                writer.write_u8(0);
+            }
+            while (writer.size() < data_start) writer.write_u8(0);
+            for (std::size_t i = 0; i < this->items_.size(); ++i) {
+                writer.write_bytes(this->items_[i].payload);
+                if (i + 1U < this->items_.size()) {
+                    while (writer.size() < offsets[i + 1U]) writer.write_u8(0);
+                }
+            }
+            return writer.take();
+        }
+
+    private:
+        struct pending_item {
+            std::string name;
+            std::vector<std::byte> payload;
+        };
+
+        std::vector<pending_item> items_;
+    };
+
+} // namespace ra3::assets
+
+

third_party/libra3assets/src/binary.cppm

@@ -0,0 +1,396 @@
+/**
+ * Compiled `BinaryAsset` streams (`Data\*.bin` + `.manifest`).
+ *
+ * Retail RA3 does not ship its gameplay/art assets as source files: the
+ * BinaryAssetBuilder compiles every XML/`.w3x` into a `.bin` *instance stream*
+ * plus a `.manifest` index (`data\static.bin`, `data\global.bin`, ...). This
+ * partition parses that index, exposes each asset's instance slice, its
+ * relocation/import sidecars and its custom-data (`cdata`) blob, and implements
+ * the Bob-Jenkins-style hash the builder names assets with.
+ *
+ * Asset names are `"Type:Instance"` (e.g. `W3DMesh:ABAIRFIELD`); `Type` is
+ * case-sensitive and `Instance` is lowercased before hashing.
+ */
+export module ra3.assets:binary;
+
+import std;
+
+import :big;
+import :bytes;
+import :error;
+import :refpack;
+
+export namespace ra3::assets {
+
+    /** The compiled instance streams a retail install ships. */
+    enum class binary_stream {
+        static_data, ///< `data\static.bin` - the main art/gameplay stream
+        global,      ///< `data\global.bin` - sounds, AI, UI
+        locale,      ///< `data\locale.bin` - localized on-demand textures
+        static_low,  ///< `data\static_l.bin` - low-detail model LODs
+        static_medium, ///< `data\static_m.bin` - medium-detail model LODs
+    };
+
+    /** The `data\<name>.manifest` stem for a stream. */
+    [[nodiscard]] inline auto to_string(binary_stream stream) -> std::string_view {
+        switch (stream) {
+        case binary_stream::static_data: return "static";
+        case binary_stream::global: return "global";
+        case binary_stream::locale: return "locale";
+        case binary_stream::static_low: return "static_l";
+        case binary_stream::static_medium: return "static_m";
+        }
+        return "static";
+    }
+
+    /** Resolve a stream name (e.g. `"global"`), or `std::nullopt`. */
+    [[nodiscard]] inline auto binary_stream_from_name(std::string_view name) -> std::optional<binary_stream> {
+        for (const auto candidate: {binary_stream::static_data, binary_stream::global, binary_stream::locale, binary_stream::static_low, binary_stream::static_medium}) {
+            if (to_string(candidate) == name) return candidate;
+        }
+        return std::nullopt;
+    }
+
+    /** Streams in the order `binary_stream_from_big` prefers when none is given. */
+    inline constexpr std::array<binary_stream, 5> binary_stream_order{binary_stream::static_data, binary_stream::global, binary_stream::locale, binary_stream::static_low,
+                                                                      binary_stream::static_medium};
+
+    /** Types compiled from a `.w3x` model source. */
+    inline constexpr std::array<std::string_view, 5> w3d_types{"W3DMesh", "W3DHierarchy", "W3DAnimation", "W3DContainer", "W3DCollisionBox"};
+
+    /**
+     * The hash BinaryAssetBuilder names assets with.
+     *
+     * A Bob-Jenkins `lookup3`-style mix. `seed` is the running value; the public
+     * overloads seed it with the length (`hash_string`).
+     */
+    [[nodiscard]] inline auto fast_hash(std::span<const std::byte> data, std::uint32_t seed = 0) -> std::uint32_t {
+        const auto length = data.size();
+        if (length == 0U) return 0x1337C0DEU;
+        const auto at16 = [&](std::size_t pos) -> std::uint32_t {
+            return static_cast<std::uint32_t>(std::to_integer<std::uint8_t>(data[pos])) |
+                   (static_cast<std::uint32_t>(std::to_integer<std::uint8_t>(data[pos + 1U])) << 8U);
+        };
+        std::uint32_t h = seed;
+        std::size_t pos = 0;
+        const auto extra = length & 3U;
+        for (std::size_t i = 0; i < (length >> 2U); ++i) {
+            h += at16(pos);
+            h ^= (at16(pos + 2U) ^ (h << 5U)) << 11U;
+            h += h >> 11U;
+            pos += 4U;
+        }
+        if (extra == 1U) {
+            h += std::to_integer<std::uint8_t>(data[pos]);
+            h ^= h << 10U;
+            h += h >> 1U;
+        } else if (extra == 2U) {
+            h += at16(pos);
+            h ^= h << 11U;
+            h += h >> 17U;
+        } else if (extra == 3U) {
+            h += at16(pos);
+            h ^= h << 16U;
+            h ^= static_cast<std::uint32_t>(std::to_integer<std::uint8_t>(data[pos + 2U])) << 18U;
+            h += h >> 11U;
+        }
+        h ^= h << 3U;
+        h += h >> 5U;
+        h ^= h << 2U;
+        h += h >> 15U;
+        h ^= h << 10U;
+        return h;
+    }
+
+    /**
+     * Hash an asset type (case-sensitive, the `TypeId`) or an instance name
+     * (`case_sensitive = false`, the `InstanceId`).
+     */
+    [[nodiscard]] inline auto hash_string(std::string_view text, bool case_sensitive = true) -> std::uint32_t {
+        std::string buffer{text};
+        if (!case_sensitive) {
+            std::ranges::transform(buffer, buffer.begin(), [](unsigned char ch) { return static_cast<char>(std::tolower(ch)); });
+        }
+        const auto *bytes = reinterpret_cast<const std::byte *>(buffer.data());
+        return fast_hash(std::span<const std::byte>{bytes, buffer.size()}, static_cast<std::uint32_t>(buffer.size()));
+    }
+
+    /** One asset in a compiled stream. */
+    struct binary_asset {
+        std::uint32_t index = 0;
+        std::uint32_t type_id = 0;
+        std::uint32_t instance_id = 0;
+        std::uint32_t type_hash = 0;
+        std::uint32_t instance_hash = 0;
+        std::vector<std::pair<std::uint32_t, std::uint32_t>> references; ///< (typeId, instanceId) pairs
+        std::string name;   ///< "Type:Instance"
+        std::string source; ///< the `.w3x`/XML it was compiled from
+        std::uint32_t instance_size = 0;
+        std::uint32_t relocation_size = 0;
+        std::uint32_t imports_size = 0;
+        bool tokenized = false;
+        std::uint32_t instance_offset = 4;   ///< into the decompressed `.bin` (after its 4-byte checksum)
+        std::uint32_t relocation_offset = 4; ///< into the `.relo`
+        std::uint32_t imports_offset = 4;    ///< into the `.imp`
+
+        [[nodiscard]] auto type_name() const -> std::string_view {
+            const auto colon = this->name.find(':');
+            return std::string_view{this->name}.substr(0, colon);
+        }
+
+        [[nodiscard]] auto instance_name() const -> std::string_view {
+            const auto colon = this->name.find(':');
+            return colon == std::string::npos ? std::string_view{this->name} : std::string_view{this->name}.substr(colon + 1U);
+        }
+
+        /**
+         * The `cdata` blob name for a custom-data asset (`AudioFile`,
+         * `OnDemandTexture`, ...):
+         * `data\<stream>\cdata\<typeId>.<typeHash>.<instanceId>.<instanceHash>.cdata`.
+         */
+        [[nodiscard]] auto cdata_name(std::string_view stream) const -> std::string {
+            return std::format("data\\{}\\cdata\\{:08x}.{:08x}.{:08x}.{:08x}.cdata", stream, this->type_id, this->type_hash, this->instance_id,
+                               this->instance_hash);
+        }
+    };
+
+    /** A callback that resolves a `cdata` blob name to its decompressed bytes. */
+    using cdata_source = std::function<std::optional<std::vector<std::byte>>(const std::string &name)>;
+
+    /**
+     * A parsed `.manifest` (+ optional `.bin`/`.relo`/`.imp`).
+     *
+     * Only the manifest is mandatory; `need_data = false` when constructing
+     * skips the (up to hundreds of megabytes) instance stream, which is all
+     * listing the assets requires.
+     */
+    class binary_container {
+    public:
+        /** Parse a manifest, its instance stream and its optional fixup streams. */
+        [[nodiscard]] static auto from_bytes(std::vector<std::byte> manifest, std::vector<std::byte> data = {}, std::vector<std::byte> relocation = {},
+                                             std::vector<std::byte> imports = {}, std::string stream = "static") -> binary_container {
+            binary_container container;
+            container.stream_ = std::move(stream);
+            container.manifest_ = std::move(manifest);
+            container.data_ = std::move(data);
+            container.relocation_ = std::move(relocation);
+            container.imports_ = std::move(imports);
+            container.parse();
+            return container;
+        }
+
+        [[nodiscard]] auto stream() const -> const std::string & { return this->stream_; }
+        [[nodiscard]] auto version() const -> std::uint16_t { return this->version_; }
+        [[nodiscard]] auto is_linked() const -> bool { return this->is_linked_; }
+        [[nodiscard]] auto assets() const -> const std::vector<binary_asset> & { return this->assets_; }
+        [[nodiscard]] auto size() const -> std::size_t { return this->assets_.size(); }
+
+        /** Count of assets per `Type` (the part before `:`). */
+        [[nodiscard]] auto type_counts() const -> std::map<std::string, std::size_t> {
+            std::map<std::string, std::size_t> counts;
+            for (const auto &asset: this->assets_) ++counts[std::string{asset.type_name()}];
+            return counts;
+        }
+
+        /** Map `(typeId << 32 | instanceId)` to the owning asset. */
+        [[nodiscard]] auto asset_index() const -> const std::unordered_map<std::uint64_t, std::size_t> & { return this->asset_index_; }
+
+        /** Every asset, in manifest order, whose `Type` matches (case-insensitive). */
+        [[nodiscard]] auto of_type(std::string_view type) const -> std::vector<const binary_asset *> {
+            std::vector<const binary_asset *> matches;
+            for (const auto &asset: this->assets_) {
+                if (std::ranges::equal(asset.type_name(), type, [](char a, char b) { return std::tolower(static_cast<unsigned char>(a)) == std::tolower(static_cast<unsigned char>(b)); }))
+                    matches.push_back(&asset);
+            }
+            return matches;
+        }
+
+        /** Resolve `"Type:Instance"` (case-sensitive, then insensitive) or `"#index"`. */
+        [[nodiscard]] auto find(std::string_view selector) const -> const binary_asset & {
+            if (selector.starts_with('#')) {
+                const auto index = static_cast<std::size_t>(std::stoul(std::string{selector.substr(1)}));
+                if (index >= this->assets_.size()) throw binary_error("asset index out of range: " + std::string{selector});
+                return this->assets_[index];
+            }
+            for (const auto &asset: this->assets_) {
+                if (asset.name == selector) return asset;
+            }
+            for (const auto &asset: this->assets_) {
+                if (std::ranges::equal(asset.name, selector, [](char a, char b) { return std::tolower(static_cast<unsigned char>(a)) == std::tolower(static_cast<unsigned char>(b)); }))
+                    return asset;
+            }
+            throw binary_error("no such asset: " + std::string{selector});
+        }
+
+        auto set_cdata_source(cdata_source source) -> void { this->cdata_ = std::move(source); }
+
+        [[nodiscard]] auto read_instance(const binary_asset &asset) const -> std::span<const std::byte> {
+            if (asset.instance_size == 0U) return {};
+            if (static_cast<std::uint64_t>(asset.instance_offset) + asset.instance_size > this->data_.size()) throw binary_error("instance extends past stream: " + asset.name);
+            return std::span<const std::byte>{this->data_}.subspan(asset.instance_offset, asset.instance_size);
+        }
+
+        [[nodiscard]] auto read_relocation(const binary_asset &asset) const -> std::span<const std::byte> {
+            if (asset.relocation_size == 0U) return {};
+            if (static_cast<std::uint64_t>(asset.relocation_offset) + asset.relocation_size > this->relocation_.size()) throw binary_error("relocation extends past stream: " + asset.name);
+            return std::span<const std::byte>{this->relocation_}.subspan(asset.relocation_offset, asset.relocation_size);
+        }
+
+        [[nodiscard]] auto read_imports(const binary_asset &asset) const -> std::span<const std::byte> {
+            if (asset.imports_size == 0U) return {};
+            if (static_cast<std::uint64_t>(asset.imports_offset) + asset.imports_size > this->imports_.size()) throw binary_error("imports extend past stream: " + asset.name);
+            return std::span<const std::byte>{this->imports_}.subspan(asset.imports_offset, asset.imports_size);
+        }
+
+        /** The asset's `cdata` blob, or `std::nullopt` when it has none. */
+        [[nodiscard]] auto read_cdata(const binary_asset &asset) const -> std::optional<std::vector<std::byte>> {
+            if (!this->cdata_) return std::nullopt;
+            return this->cdata_(asset.cdata_name(this->stream_));
+        }
+
+        /** The asset's real payload: its `cdata` blob when present, else its instance. */
+        [[nodiscard]] auto read_payload(const binary_asset &asset) const -> std::vector<std::byte> {
+            if (auto cdata = this->read_cdata(asset)) return *cdata;
+            const auto instance = this->read_instance(asset);
+            return {instance.begin(), instance.end()};
+        }
+
+    private:
+        binary_container() = default;
+
+        auto parse() -> void {
+            byte_reader reader{this->manifest_};
+            const auto is_big_endian = reader.read_u8();
+            this->is_linked_ = reader.read_bool();
+            this->version_ = reader.read_u16();
+            if (is_big_endian != 0U) throw binary_error("big-endian manifests are not supported");
+            if (this->version_ != 5U && this->version_ != 6U) throw binary_error("unsupported manifest version " + std::to_string(this->version_));
+            (void) reader.read_u32(); // stream checksum
+            (void) reader.read_u32(); // all-types hash
+            const auto count = reader.read_u32();
+            (void) reader.read_u32(); // total instance data size
+            (void) reader.read_u32(); // max instance chunk size
+            (void) reader.read_u32(); // max relocation chunk size
+            (void) reader.read_u32(); // max imports chunk size
+            const auto reference_buffer_size = reader.read_u32();
+            const auto reference_name_buffer_size = reader.read_u32();
+            const auto name_buffer_size = reader.read_u32();
+            const auto source_buffer_size = reader.read_u32();
+
+            constexpr std::size_t header_size = 48U;
+            constexpr std::size_t entry_size = 48U;
+            if (this->manifest_.size() < header_size + static_cast<std::size_t>(count) * entry_size) throw binary_error("manifest entry table is truncated");
+
+            const auto entries_off = header_size;
+            const auto references_off = entries_off + static_cast<std::size_t>(count) * entry_size;
+            const auto reference_names_off = references_off + reference_buffer_size;
+            const auto names_off = reference_names_off + reference_name_buffer_size;
+            const auto sources_off = names_off + name_buffer_size;
+            if (sources_off + source_buffer_size > this->manifest_.size()) throw binary_error("manifest string buffers are truncated");
+
+            const auto cstr = [&](std::size_t base, std::int32_t offset) -> std::string {
+                if (offset < 0) return {};
+                const auto start = base + static_cast<std::size_t>(offset);
+                if (start >= this->manifest_.size()) return {};
+                std::size_t end = start;
+                while (end < this->manifest_.size() && std::to_integer<std::uint8_t>(this->manifest_[end]) != 0U) ++end;
+                return std::string{reinterpret_cast<const char *>(this->manifest_.data() + start), end - start};
+            };
+
+            this->assets_.reserve(count);
+            std::uint32_t instance_offset = 4;
+            std::uint32_t relocation_offset = 4;
+            std::uint32_t imports_offset = 4;
+            for (std::uint32_t i = 0; i < count; ++i) {
+                byte_reader entry{std::span<const std::byte>{this->manifest_}.subspan(entries_off + static_cast<std::size_t>(i) * entry_size, entry_size)};
+                binary_asset asset;
+                asset.index = i;
+                asset.type_id = entry.read_u32();
+                asset.instance_id = entry.read_u32();
+                asset.type_hash = entry.read_u32();
+                asset.instance_hash = entry.read_u32();
+                const auto reference_offset = entry.read_i32();
+                const auto reference_count = entry.read_i32();
+                const auto name_offset = entry.read_i32();
+                const auto source_offset = entry.read_i32();
+                asset.instance_size = entry.read_u32();
+                asset.relocation_size = entry.read_u32();
+                asset.imports_size = entry.read_u32();
+                asset.tokenized = entry.read_u32() != 0U;
+                asset.name = cstr(names_off, name_offset);
+                asset.source = cstr(sources_off, source_offset);
+                asset.instance_offset = instance_offset;
+                asset.relocation_offset = relocation_offset;
+                asset.imports_offset = imports_offset;
+                instance_offset += asset.instance_size;
+                relocation_offset += asset.relocation_size;
+                imports_offset += asset.imports_size;
+
+                for (std::int32_t j = 0; j < reference_count; ++j) {
+                    byte_reader ref{std::span<const std::byte>{this->manifest_}.subspan(references_off + static_cast<std::size_t>(reference_offset) +
+                                                                                          static_cast<std::size_t>(j) * 8U,
+                                                                                      8U)};
+                    asset.references.emplace_back(ref.read_u32(), ref.read_u32());
+                }
+                this->asset_index_.emplace((static_cast<std::uint64_t>(asset.type_id) << 32U) | asset.instance_id, this->assets_.size());
+                this->assets_.push_back(std::move(asset));
+            }
+        }
+
+        std::string stream_ = "static";
+        std::vector<std::byte> manifest_;
+        std::vector<std::byte> data_;
+        std::vector<std::byte> relocation_;
+        std::vector<std::byte> imports_;
+        std::uint16_t version_ = 0;
+        bool is_linked_ = false;
+        std::vector<binary_asset> assets_;
+        std::unordered_map<std::uint64_t, std::size_t> asset_index_;
+        cdata_source cdata_;
+    };
+
+    namespace detail {
+        [[nodiscard]] inline auto pick_manifest(std::string_view stream) -> std::string { return std::format("data\\{}.manifest", stream); }
+    }
+
+    /**
+     * Load one BinaryAsset stream out of a `BIG4` archive.
+     *
+     * `stream` selects the `.manifest` (default: the first of
+     * `binary_stream_order` found). When `need_data` is false only the manifest
+     * is read, which is enough to enumerate assets without decompressing the
+     * multi-hundred-megabyte instance stream.
+     *
+     * The returned container keeps a `cdata` reader that borrows `archive`; keep
+     * the archive alive for as long as the container is used.
+     */
+    [[nodiscard]] inline auto binary_stream_from_big(const big_archive &archive, std::optional<binary_stream> stream = std::nullopt, bool need_data = true) -> binary_container {
+        std::optional<binary_stream> chosen = stream;
+        if (!chosen) {
+            for (const auto candidate: binary_stream_order) {
+                if (archive.contains(detail::pick_manifest(to_string(candidate)))) {
+                    chosen = candidate;
+                    break;
+                }
+            }
+        }
+        if (!chosen) throw binary_error("archive has no known .manifest entry");
+
+        const auto manifest_name = detail::pick_manifest(to_string(*chosen));
+        const auto base = manifest_name.substr(0, manifest_name.size() - std::string_view{".manifest"}.size());
+        const auto manifest = maybe_decompress(archive.read(manifest_name, false));
+        std::vector<std::byte> data;
+        if (need_data) data = maybe_decompress(archive.read(base + ".bin", false));
+        const auto relocation = maybe_decompress(archive.read(base + ".relo", false));
+        const auto imports = maybe_decompress(archive.read(base + ".imp", false));
+
+        auto container = binary_container::from_bytes(std::move(manifest), std::move(data), std::move(relocation), std::move(imports), std::string{to_string(*chosen)});
+        container.set_cdata_source([&archive](const std::string &name) -> std::optional<std::vector<std::byte>> {
+            const auto *entry = archive.find_exact(name);
+            if (entry == nullptr) return std::nullopt;
+            return maybe_decompress(archive.read(*entry, false));
+        });
+        return container;
+    }
+
+} // namespace ra3::assets

third_party/libra3assets/src/bytes.cppm

@@ -0,0 +1,220 @@
+/**
+ * Bounds-checked little-/big-endian byte readers and writers.
+ *
+ * Red Alert 3's asset formats are little-endian, with one notable exception:
+ * the `BIG4` index stores its counts, offsets and sizes big-endian. Both byte
+ * orders are provided here. Every read is bounds-checked and throws
+ * `format_error` rather than reading past the end of the buffer.
+ */
+export module ra3.assets:bytes;
+
+import std;
+
+import :error;
+
+export namespace ra3::assets {
+
+    /** A cursor over a read-only byte range with checked accessors. */
+    class byte_reader {
+    public:
+        explicit byte_reader(std::span<const std::byte> data)
+            : data_(data) {
+        }
+
+        [[nodiscard]] auto size() const -> std::size_t { return this->data_.size(); }
+        [[nodiscard]] auto position() const -> std::size_t { return this->pos_; }
+        [[nodiscard]] auto remaining() const -> std::size_t { return this->data_.size() - this->pos_; }
+        [[nodiscard]] auto empty() const -> bool { return this->pos_ >= this->data_.size(); }
+
+        auto seek(std::size_t at) -> void {
+            if (at > this->data_.size()) throw format_error("seek past end of buffer");
+            this->pos_ = at;
+        }
+
+        auto skip(std::size_t count) -> void {
+            this->require(count);
+            this->pos_ += count;
+        }
+
+        [[nodiscard]] auto read_u8() -> std::uint8_t {
+            this->require(1);
+            return std::to_integer<std::uint8_t>(this->data_[this->pos_++]);
+        }
+
+        [[nodiscard]] auto read_bool() -> bool { return this->read_u8() != 0U; }
+
+        [[nodiscard]] auto read_u16() -> std::uint16_t {
+            return static_cast<std::uint16_t>(this->read_le(2));
+        }
+
+        [[nodiscard]] auto read_u24() -> std::uint32_t { return this->read_le(3); }
+
+        [[nodiscard]] auto read_u32() -> std::uint32_t { return this->read_le(4); }
+
+        [[nodiscard]] auto read_u64() -> std::uint64_t { return this->read_le(8); }
+
+        [[nodiscard]] auto read_i16() -> std::int16_t { return static_cast<std::int16_t>(this->read_u16()); }
+
+        [[nodiscard]] auto read_i32() -> std::int32_t { return static_cast<std::int32_t>(this->read_u32()); }
+
+        [[nodiscard]] auto read_f32() -> float { return std::bit_cast<float>(this->read_u32()); }
+
+        [[nodiscard]] auto read_be_u16() -> std::uint16_t { return static_cast<std::uint16_t>(this->read_be(2)); }
+        [[nodiscard]] auto read_be_u32() -> std::uint32_t { return this->read_be(4); }
+
+        /** A view of the next `count` bytes; the cursor advances past them. */
+        [[nodiscard]] auto read_bytes(std::size_t count) -> std::span<const std::byte> {
+            this->require(count);
+            const auto view = this->data_.subspan(this->pos_, count);
+            this->pos_ += count;
+            return view;
+        }
+
+        /** `count` bytes decoded as Latin-1 (one byte per character). */
+        [[nodiscard]] auto read_ascii(std::size_t count) -> std::string {
+            const auto view = this->read_bytes(count);
+            return std::string{reinterpret_cast<const char *>(view.data()), view.size()};
+        }
+
+        /** A `u16`-length-prefixed ASCII string. */
+        [[nodiscard]] auto read_u16_prefixed_ascii() -> std::string { return this->read_ascii(this->read_u16()); }
+
+        /** A `u16`-length-prefixed string, decoded as UTF-8 (ASCII-compatible). */
+        [[nodiscard]] auto read_u16_prefixed_ascii_as_utf8() -> std::string { return this->read_u16_prefixed_ascii(); }
+
+        /** A `u16`-length-prefixed UTF-16LE string (length counted in code units). */
+        [[nodiscard]] auto read_u16_prefixed_utf16() -> std::u16string {
+            const auto count = this->read_u16();
+            this->require(static_cast<std::size_t>(count) * 2U);
+            std::u16string text(count, u'\0');
+            for (std::uint16_t i = 0; i < count; ++i) text[i] = static_cast<char16_t>(this->read_u16());
+            return text;
+        }
+
+        /** A NUL-terminated ASCII string; the cursor stops just past the NUL. */
+        [[nodiscard]] auto read_cstring() -> std::string {
+            std::string text;
+            while (this->pos_ < this->data_.size()) {
+                const auto ch = static_cast<char>(this->read_u8());
+                if (ch == '\0') break;
+                text.push_back(ch);
+            }
+            return text;
+        }
+
+    private:
+        auto require(std::size_t count) const -> void {
+            if (this->pos_ + count > this->data_.size()) throw format_error("unexpected end of buffer");
+        }
+
+        [[nodiscard]] auto read_le(std::size_t width) -> std::uint64_t {
+            this->require(width);
+            std::uint64_t value = 0;
+            for (std::size_t i = 0; i < width; ++i) value |= static_cast<std::uint64_t>(std::to_integer<std::uint8_t>(this->data_[this->pos_ + i])) << (8U * i);
+            this->pos_ += width;
+            return value;
+        }
+
+        [[nodiscard]] auto read_be(std::size_t width) -> std::uint64_t {
+            this->require(width);
+            std::uint64_t value = 0;
+            for (std::size_t i = 0; i < width; ++i) value = (value << 8U) | static_cast<std::uint64_t>(std::to_integer<std::uint8_t>(this->data_[this->pos_ + i]));
+            this->pos_ += width;
+            return value;
+        }
+
+        std::span<const std::byte> data_;
+        std::size_t pos_ = 0;
+    };
+
+    /** An append-only little-endian byte buffer. */
+    class byte_writer {
+    public:
+        [[nodiscard]] auto size() const -> std::size_t { return this->buffer_.size(); }
+        [[nodiscard]] auto data() const -> std::span<const std::byte> { return this->buffer_; }
+        [[nodiscard]] auto take() -> std::vector<std::byte> { return std::move(this->buffer_); }
+
+        auto write_u8(std::uint8_t value) -> void { this->buffer_.push_back(static_cast<std::byte>(value)); }
+
+        auto write_bool(bool value) -> void { this->write_u8(value ? 1U : 0U); }
+
+        auto write_u16(std::uint16_t value) -> void { this->write_le(value, 2); }
+        auto write_u24(std::uint32_t value) -> void { this->write_le(value, 3); }
+        auto write_u32(std::uint32_t value) -> void { this->write_le(value, 4); }
+        auto write_u64(std::uint64_t value) -> void { this->write_le(value, 8); }
+        auto write_i16(std::int16_t value) -> void { this->write_u16(static_cast<std::uint16_t>(value)); }
+        auto write_i32(std::int32_t value) -> void { this->write_u32(static_cast<std::uint32_t>(value)); }
+        auto write_f32(float value) -> void { this->write_u32(std::bit_cast<std::uint32_t>(value)); }
+
+        auto write_bytes(std::span<const std::byte> bytes) -> void { this->buffer_.insert(this->buffer_.end(), bytes.begin(), bytes.end()); }
+
+        auto write_ascii(std::string_view text) -> void {
+            for (const auto ch: text) this->buffer_.push_back(static_cast<std::byte>(static_cast<unsigned char>(ch)));
+        }
+
+        auto write_u16_prefixed_ascii(std::string_view text) -> void {
+            this->write_u16(static_cast<std::uint16_t>(text.size()));
+            this->write_ascii(text);
+        }
+
+        auto write_u16_prefixed_utf16(std::u16string_view text) -> void {
+            this->write_u16(static_cast<std::uint16_t>(text.size()));
+            for (const auto unit: text) {
+                this->write_u16(static_cast<std::uint16_t>(unit));
+            }
+        }
+
+        /** Overwrite a previously written `u32` (used to backpatch sizes). */
+        auto patch_u32(std::size_t offset, std::uint32_t value) -> void {
+            if (offset + 4U > this->buffer_.size()) throw format_error("patch offset past end of buffer");
+            for (std::size_t i = 0; i < 4U; ++i) this->buffer_[offset + i] = static_cast<std::byte>((value >> (8U * i)) & 0xFFU);
+        }
+
+    private:
+        auto write_le(std::uint64_t value, std::size_t width) -> void {
+            for (std::size_t i = 0; i < width; ++i) this->buffer_.push_back(static_cast<std::byte>((value >> (8U * i)) & 0xFFU));
+        }
+
+        std::vector<std::byte> buffer_;
+    };
+
+    /** Convenience: encode a UTF-8 string (ASCII subset) as UTF-16LE code units. */
+    [[nodiscard]] inline auto to_utf16(std::string_view text) -> std::u16string {
+        std::u16string out;
+        out.reserve(text.size());
+        for (const auto ch: text) out.push_back(static_cast<char16_t>(static_cast<unsigned char>(ch)));
+        return out;
+    }
+
+    /** Convenience: narrow a UTF-16 string that is known to be within Latin-1. */
+    [[nodiscard]] inline auto to_ascii(std::u16string_view text) -> std::string {
+        std::string out;
+        out.reserve(text.size());
+        for (const auto unit: text) out.push_back(static_cast<char>(unit & 0xFFU));
+        return out;
+    }
+
+    /** Read a whole file as bytes. */
+    [[nodiscard]] inline auto read_file(const std::filesystem::path &path) -> std::vector<std::byte> {
+        std::ifstream in(path, std::ios::binary);
+        if (!in) throw format_error("cannot open file: " + path.string());
+        in.seekg(0, std::ios::end);
+        const auto end = in.tellg();
+        if (end < 0) throw format_error("cannot size file: " + path.string());
+        std::vector<std::byte> bytes(static_cast<std::size_t>(end));
+        in.seekg(0, std::ios::beg);
+        if (!bytes.empty()) in.read(reinterpret_cast<char *>(bytes.data()), static_cast<std::streamsize>(bytes.size()));
+        return bytes;
+    }
+
+    /** Write bytes to a file, creating parent directories as needed. */
+    inline auto write_file(const std::filesystem::path &path, std::span<const std::byte> bytes) -> void {
+        std::error_code ec;
+        if (!path.parent_path().empty()) std::filesystem::create_directories(path.parent_path(), ec);
+        std::ofstream out(path, std::ios::binary);
+        if (!out) throw format_error("cannot write file: " + path.string());
+        out.write(reinterpret_cast<const char *>(bytes.data()), static_cast<std::streamsize>(bytes.size()));
+        if (!out) throw format_error("cannot write file: " + path.string());
+    }
+
+} // namespace ra3::assets

third_party/libra3assets/src/csf.cppm

@@ -0,0 +1,180 @@
+/**
+ * SAGE `.csf` string tables (`data\gamestrings.csf`).
+ *
+ * The compressed unit/label localization table Red Alert 3 ships per language
+ * in `Lang-*.big` / `English.big`. Each value is a UTF-16 string whose every
+ * code unit is bit-inverted (`code ^ 0xFFFF`); labels are plain ASCII and are
+ * matched case-insensitively.
+ */
+export module ra3.assets:csf;
+
+import std;
+
+import :big;
+import :bytes;
+import :error;
+import :refpack;
+
+export namespace ra3::assets {
+
+    /** Magic of the label block (`" LBL"` little-endian). */
+    inline constexpr std::uint32_t csf_label_flag = 0x4C424C20U;
+
+    /** Magic of a value block (`" RTS"` little-endian). */
+    inline constexpr std::uint32_t csf_value_flag = 0x53545220U;
+
+    /** One label and its (usually single) string value. */
+    struct csf_entry {
+        std::string label;
+        std::vector<std::u16string> values;
+
+        /** The concatenation of every value block, the way the game renders it. */
+        [[nodiscard]] auto value() const -> std::u16string {
+            std::u16string joined;
+            for (const auto &chunk: this->values) joined += chunk;
+            return joined;
+        }
+    };
+
+    /** Decode a UTF-16 string (with surrogate pairs) to UTF-8. */
+    [[nodiscard]] inline auto utf16_to_utf8(std::u16string_view text) -> std::string {
+        std::string out;
+        for (std::size_t i = 0; i < text.size(); ++i) {
+            auto code = static_cast<std::uint32_t>(text[i]);
+            if (code >= 0xD800U && code <= 0xDBFFU && i + 1U < text.size()) {
+                const auto low = static_cast<std::uint32_t>(text[i + 1U]);
+                if (low >= 0xDC00U && low <= 0xDFFFU) {
+                    code = 0x10000U + ((code - 0xD800U) << 10U) + (low - 0xDC00U);
+                    ++i;
+                }
+            }
+            if (code < 0x80U) {
+                out.push_back(static_cast<char>(code));
+            } else if (code < 0x800U) {
+                out.push_back(static_cast<char>(0xC0U | (code >> 6U)));
+                out.push_back(static_cast<char>(0x80U | (code & 0x3FU)));
+            } else if (code < 0x10000U) {
+                out.push_back(static_cast<char>(0xE0U | (code >> 12U)));
+                out.push_back(static_cast<char>(0x80U | ((code >> 6U) & 0x3FU)));
+                out.push_back(static_cast<char>(0x80U | (code & 0x3FU)));
+            } else {
+                out.push_back(static_cast<char>(0xF0U | (code >> 18U)));
+                out.push_back(static_cast<char>(0x80U | ((code >> 12U) & 0x3FU)));
+                out.push_back(static_cast<char>(0x80U | ((code >> 6U) & 0x3FU)));
+                out.push_back(static_cast<char>(0x80U | (code & 0x3FU)));
+            }
+        }
+        return out;
+    }
+
+    /**
+     * A parsed `.csf` table.
+     *
+     * Labels are stored verbatim; lookup upper-cases the key because the engine
+     * treats them case-insensitively.
+     */
+    class csf_table {
+    public:
+        /** Parse a `.csf` image. */
+        [[nodiscard]] static auto parse(std::span<const std::byte> bytes) -> csf_table {
+            byte_reader reader{bytes};
+            const auto magic = reader.read_ascii(4);
+            if (magic != "CSF " && magic != " FSC") throw csf_error("not a CSF file");
+            csf_table table;
+            table.version_ = reader.read_u32();
+            const auto num_labels = reader.read_u32();
+            (void) reader.read_u32(); // number of value blocks
+            (void) reader.read_u32(); // reserved
+            (void) reader.read_u32(); // reserved
+            table.entries_.reserve(num_labels);
+            for (std::uint32_t i = 0; i < num_labels; ++i) {
+                (void) reader.read_u32(); // label flag (" LBL")
+                const auto value_count = reader.read_u32();
+                const auto label_length = reader.read_u32();
+                csf_entry entry;
+                entry.label = reader.read_ascii(label_length);
+                entry.values.reserve(value_count);
+                for (std::uint32_t j = 0; j < value_count; ++j) {
+                    (void) reader.read_u32(); // value flag (" RTS")
+                    const auto char_count = reader.read_u32();
+                    std::u16string value(char_count, u'\0');
+                    for (std::uint32_t k = 0; k < char_count; ++k) value[k] = static_cast<char16_t>(reader.read_u16() ^ 0xFFFFU);
+                    entry.values.push_back(std::move(value));
+                }
+                table.entries_.push_back(std::move(entry));
+            }
+            table.reindex();
+            return table;
+        }
+
+        /** Read and parse a `.csf` file from disk. */
+        [[nodiscard]] static auto open(const std::filesystem::path &path) -> csf_table {
+            return csf_table::parse(read_file(path));
+        }
+
+        /** Load `data\gamestrings.csf` out of an archive. */
+        [[nodiscard]] static auto from_big(const big_archive &archive, std::string_view entry = "data\\gamestrings.csf") -> csf_table {
+            return csf_table::parse(maybe_decompress(archive.read(entry, false)));
+        }
+
+        /** Serialise the table back to a `.csf` image. */
+        [[nodiscard]] auto write() const -> std::vector<std::byte> {
+            byte_writer writer;
+            writer.write_ascii(" FSC");
+            writer.write_u32(this->version_);
+            writer.write_u32(static_cast<std::uint32_t>(this->entries_.size()));
+            std::uint32_t value_count = 0;
+            for (const auto &entry: this->entries_) value_count += static_cast<std::uint32_t>(entry.values.size());
+            writer.write_u32(value_count);
+            writer.write_u32(0);
+            writer.write_u32(0);
+            for (const auto &entry: this->entries_) {
+                writer.write_u32(csf_label_flag);
+                writer.write_u32(static_cast<std::uint32_t>(entry.values.size()));
+                writer.write_u32(static_cast<std::uint32_t>(entry.label.size()));
+                writer.write_ascii(entry.label);
+                for (const auto &value: entry.values) {
+                    writer.write_u32(csf_value_flag);
+                    writer.write_u32(static_cast<std::uint32_t>(value.size()));
+                    for (const auto unit: value) writer.write_u16(static_cast<std::uint16_t>(unit) ^ 0xFFFFU);
+                }
+            }
+            return writer.take();
+        }
+
+        [[nodiscard]] auto version() const -> std::uint32_t { return this->version_; }
+        [[nodiscard]] auto entries() const -> const std::vector<csf_entry> & { return this->entries_; }
+        [[nodiscard]] auto size() const -> std::size_t { return this->entries_.size(); }
+
+        /** The entry for `label`, or `nullptr`; the match is case-insensitive. */
+        [[nodiscard]] auto find(std::string_view label) const -> const csf_entry * {
+            auto key = std::string{label};
+            std::ranges::transform(key, key.begin(), [](unsigned char ch) { return static_cast<char>(std::toupper(ch)); });
+            const auto it = this->index_.find(key);
+            return it == this->index_.end() ? nullptr : &this->entries_[it->second];
+        }
+
+        /** The UTF-8 value for `label`, or `fallback` when absent. */
+        [[nodiscard]] auto lookup(std::string_view label, std::string fallback = {}) const -> std::string {
+            const auto *entry = this->find(label);
+            if (entry == nullptr) return fallback;
+            auto text = utf16_to_utf8(entry->value());
+            return text.empty() ? std::move(fallback) : text;
+        }
+
+    private:
+        auto reindex() -> void {
+            this->index_.clear();
+            for (std::size_t i = 0; i < this->entries_.size(); ++i) {
+                auto key = this->entries_[i].label;
+                std::ranges::transform(key, key.begin(), [](unsigned char ch) { return static_cast<char>(std::toupper(ch)); });
+                this->index_.try_emplace(std::move(key), i);
+            }
+        }
+
+        std::uint32_t version_ = 3;
+        std::vector<csf_entry> entries_;
+        std::unordered_map<std::string, std::size_t> index_;
+    };
+
+} // namespace ra3::assets

third_party/libra3assets/src/error.cppm

@@ -0,0 +1,56 @@
+/**
+ * Exception hierarchy of libra3assets.
+ *
+ * Every failure the library reports derives from `asset_error` (itself a
+ * `std::runtime_error`), so a caller can catch the whole family with one
+ * handler and still discriminate by the concrete type when it matters.
+ */
+export module ra3.assets:error;
+
+import std;
+
+export namespace ra3::assets {
+
+    /** Base class of every failure libra3assets reports. */
+    class asset_error: public std::runtime_error {
+    public:
+        using std::runtime_error::runtime_error;
+    };
+
+    /** A byte range is not a well-formed Red Alert 3 asset. */
+    class format_error: public asset_error {
+    public:
+        using asset_error::asset_error;
+    };
+
+    /** An EA RefPack stream is malformed or its length disagrees. */
+    class refpack_error: public asset_error {
+    public:
+        using asset_error::asset_error;
+    };
+
+    /** A `BIG4` archive is malformed, truncated or missing an entry. */
+    class big_error: public asset_error {
+    public:
+        using asset_error::asset_error;
+    };
+
+    /** A compiled `BinaryAsset` manifest/stream is malformed. */
+    class binary_error: public asset_error {
+    public:
+        using asset_error::asset_error;
+    };
+
+    /** A SAGE `.csf` string table is malformed. */
+    class csf_error: public asset_error {
+    public:
+        using asset_error::asset_error;
+    };
+
+    /** A SAGE `.map` container or one of its chunks is malformed. */
+    class map_error: public asset_error {
+    public:
+        using asset_error::asset_error;
+    };
+
+} // namespace ra3::assets

third_party/libra3assets/src/map.cppm

@@ -0,0 +1,778 @@
+/**
+ * SAGE `.map` containers - the core of the map editor.
+ *
+ * A `.map` is a `CkMp` chunk tree. On disk it may be wrapped twice: inside a
+ * `BIG4` the payload is one RefPack stream; the `.map` file it yields is either
+ * a bare `CkMp` tree or an `EAR\0`-wrapped RefPack stream around one. This
+ * partition unwraps all three shapes and models the tree as an ordered list of
+ * named, versioned chunks.
+ *
+ * The container round-trips losslessly: chunks this library does not model are
+ * preserved byte-for-byte, and the asset-name table keeps its original indices
+ * so unparsed chunks (which embed name indices) stay valid. On top of the
+ * container sit typed accessors for the chunks a map editor needs:
+ * `HeightMapData` (the terrain grid), `ObjectsList` (every placed prop, building
+ * and `*Waypoints/Waypoint`), `MPPositionList`, `WorldInfo` and `WaypointsList`.
+ */
+export module ra3.assets:map;
+
+import std;
+
+import :big;
+import :bytes;
+import :error;
+import :refpack;
+
+export namespace ra3::assets {
+
+    /** A world-space coordinate. */
+    struct coord3d {
+        float x = 0.0F;
+        float y = 0.0F;
+        float z = 0.0F;
+    };
+
+    /**
+     * A map object's `RoadType` bit flags.
+     *
+     * Zero for most objects; set on objects the terrain road system connects
+     * (`Start`/`End`/`BridgeStart`/`BridgeEnd`/`Angled`/`TightCurve`/`EndCap`).
+     */
+    enum class road_type : std::uint32_t {
+        none = 0,
+        start = 2,
+        end = 4,
+        angled = 8,
+        bridge_start = 16,
+        bridge_end = 32,
+        tight_curve = 64,
+        end_cap = 128,
+        unknown3 = 256,
+        unknown4 = 512,
+    };
+
+    [[nodiscard]] constexpr auto operator|(road_type a, road_type b) -> road_type {
+        return static_cast<road_type>(static_cast<std::uint32_t>(a) | static_cast<std::uint32_t>(b));
+    }
+    [[nodiscard]] constexpr auto operator&(road_type a, road_type b) -> road_type {
+        return static_cast<road_type>(static_cast<std::uint32_t>(a) & static_cast<std::uint32_t>(b));
+    }
+
+    /** True when `value` has every bit of `flag` set. */
+    [[nodiscard]] constexpr auto has_flag(road_type value, road_type flag) -> bool {
+        return (static_cast<std::uint32_t>(value) & static_cast<std::uint32_t>(flag)) != 0U;
+    }
+
+    /** The `CkMp` chunk types SAGE defines, plus `unknown` for anything else. */
+    enum class chunk_kind {
+        asset_list,
+        global_version,
+        height_map_data,
+        blend_tile_data,
+        world_info,
+        mp_position_list,
+        sides_list,
+        library_map_lists,
+        teams,
+        player_scripts_list,
+        build_lists,
+        objects_list,
+        polygon_triggers,
+        trigger_areas,
+        global_water_settings,
+        fog_settings,
+        mission_hot_spots,
+        mission_objectives,
+        standing_water_areas,
+        river_areas,
+        standing_wave_areas,
+        global_lighting,
+        post_effects_chunk,
+        environment_data,
+        named_cameras,
+        camera_animation_list,
+        castle_templates,
+        waypoints_list,
+        skybox_settings,
+        unknown,
+    };
+
+    /** The canonical chunk name (the `unknown` kind has no name). */
+    [[nodiscard]] inline auto to_string(chunk_kind kind) -> std::string_view {
+        switch (kind) {
+        case chunk_kind::asset_list: return "AssetList";
+        case chunk_kind::global_version: return "GlobalVersion";
+        case chunk_kind::height_map_data: return "HeightMapData";
+        case chunk_kind::blend_tile_data: return "BlendTileData";
+        case chunk_kind::world_info: return "WorldInfo";
+        case chunk_kind::mp_position_list: return "MPPositionList";
+        case chunk_kind::sides_list: return "SidesList";
+        case chunk_kind::library_map_lists: return "LibraryMapLists";
+        case chunk_kind::teams: return "Teams";
+        case chunk_kind::player_scripts_list: return "PlayerScriptsList";
+        case chunk_kind::build_lists: return "BuildLists";
+        case chunk_kind::objects_list: return "ObjectsList";
+        case chunk_kind::polygon_triggers: return "PolygonTriggers";
+        case chunk_kind::trigger_areas: return "TriggerAreas";
+        case chunk_kind::global_water_settings: return "GlobalWaterSettings";
+        case chunk_kind::fog_settings: return "FogSettings";
+        case chunk_kind::mission_hot_spots: return "MissionHotSpots";
+        case chunk_kind::mission_objectives: return "MissionObjectives";
+        case chunk_kind::standing_water_areas: return "StandingWaterAreas";
+        case chunk_kind::river_areas: return "RiverAreas";
+        case chunk_kind::standing_wave_areas: return "StandingWaveAreas";
+        case chunk_kind::global_lighting: return "GlobalLighting";
+        case chunk_kind::post_effects_chunk: return "PostEffectsChunk";
+        case chunk_kind::environment_data: return "EnvironmentData";
+        case chunk_kind::named_cameras: return "NamedCameras";
+        case chunk_kind::camera_animation_list: return "CameraAnimationList";
+        case chunk_kind::castle_templates: return "CastleTemplates";
+        case chunk_kind::waypoints_list: return "WaypointsList";
+        case chunk_kind::skybox_settings: return "SkyboxSettings";
+        case chunk_kind::unknown: break;
+        }
+        return {};
+    }
+
+    /** Classify a chunk name. */
+    [[nodiscard]] inline auto chunk_kind_of(std::string_view name) -> chunk_kind {
+        for (int i = 0; i < static_cast<int>(chunk_kind::unknown); ++i) {
+            const auto kind = static_cast<chunk_kind>(i);
+            if (to_string(kind) == name) return kind;
+        }
+        return chunk_kind::unknown;
+    }
+
+    /** The map's asset-name table: `index -> name`, indices preserved on write. */
+    class name_table {
+    public:
+        [[nodiscard]] auto name(std::uint32_t index) const -> std::string_view {
+            if (index >= this->names_.size()) throw map_error("asset name index out of range: " + std::to_string(index));
+            return this->names_[index];
+        }
+
+        /** The existing index of `name`, or a freshly appended one. */
+        [[nodiscard]] auto get_or_create(std::string_view name) -> std::uint32_t {
+            for (std::uint32_t i = 1; i < this->names_.size(); ++i) {
+                if (this->names_[i] == name) return i;
+            }
+            this->names_.emplace_back(name);
+            return static_cast<std::uint32_t>(this->names_.size() - 1U);
+        }
+
+        [[nodiscard]] auto entries() const -> const std::vector<std::string> & { return this->names_; }
+        [[nodiscard]] auto size() const -> std::size_t { return this->names_.empty() ? 0U : this->names_.size() - 1U; }
+
+        /** Resize the table (used while parsing); index 0 stays the unused slot. */
+        auto resize(std::size_t count) -> void { this->names_.resize(count); }
+
+        /** Assign the name at `index` (used while parsing). */
+        auto set_name(std::uint32_t index, std::string name) -> void { this->names_.at(index) = std::move(name); }
+
+    private:
+        std::vector<std::string> names_{std::string{}}; // index 0 is unused
+    };
+
+    /** One `CkMp` chunk: a named, versioned, opaque payload. */
+    struct map_chunk {
+        std::string name;
+        chunk_kind kind = chunk_kind::unknown;
+        std::uint32_t asset_index = 0;
+        std::uint16_t version = 0;
+        std::vector<std::byte> payload;
+    };
+
+    /** A `HeightMapData` border rectangle. */
+    struct height_map_border {
+        std::uint32_t corner1_x = 0;
+        std::uint32_t corner1_y = 0;
+        std::uint32_t x = 0;
+        std::uint32_t y = 0;
+    };
+
+    /** The parsed `HeightMapData` chunk: the terrain elevation grid. */
+    struct height_map_data {
+        std::uint32_t width = 0;
+        std::uint32_t height = 0;
+        std::uint32_t border_width = 0;
+        std::vector<height_map_border> borders;
+        std::vector<std::uint16_t> elevations; ///< `width * height`, row-major (y outer, x inner)
+        std::uint16_t version = 6;
+
+        /** Metres per elevation unit (uint16 grids scale by 0.0390625). */
+        [[nodiscard]] auto vertical_scale() const -> float { return this->version >= 5U ? 0.0390625F : 0.625F; }
+
+        [[nodiscard]] auto at(std::uint32_t x, std::uint32_t y) const -> std::uint16_t { return this->elevations.at(static_cast<std::size_t>(y) * this->width + x); }
+        auto set(std::uint32_t x, std::uint32_t y, std::uint16_t value) -> void { this->elevations.at(static_cast<std::size_t>(y) * this->width + x) = value; }
+
+        /** Parse a `HeightMapData` chunk payload. */
+        [[nodiscard]] static auto parse(std::uint16_t version, std::span<const std::byte> payload) -> height_map_data {
+            byte_reader reader{payload};
+            height_map_data data;
+            data.version = version;
+            data.width = reader.read_u32();
+            data.height = reader.read_u32();
+            data.border_width = reader.read_u32();
+            const auto border_count = reader.read_u32();
+            data.borders.reserve(border_count);
+            for (std::uint32_t i = 0; i < border_count; ++i) {
+                height_map_border border;
+                if (version >= 6U) {
+                    border.corner1_x = reader.read_u32();
+                    border.corner1_y = reader.read_u32();
+                }
+                border.x = reader.read_u32();
+                border.y = reader.read_u32();
+                data.borders.push_back(border);
+            }
+            const auto area = reader.read_u32();
+            const auto expected = static_cast<std::uint64_t>(data.width) * data.height;
+            if (area != expected) throw map_error("HeightMapData area does not match width * height");
+            data.elevations.resize(static_cast<std::size_t>(expected));
+            for (std::uint32_t y = 0; y < data.height; ++y) {
+                for (std::uint32_t x = 0; x < data.width; ++x) {
+                    data.elevations[static_cast<std::size_t>(y) * data.width + x] = version >= 5U ? reader.read_u16() : reader.read_u8();
+                }
+            }
+            return data;
+        }
+
+        /** Serialise the chunk payload (without the 10-byte chunk header). */
+        [[nodiscard]] auto serialize() const -> std::vector<std::byte> {
+            byte_writer writer;
+            writer.write_u32(this->width);
+            writer.write_u32(this->height);
+            writer.write_u32(this->border_width);
+            writer.write_u32(static_cast<std::uint32_t>(this->borders.size()));
+            for (const auto &border: this->borders) {
+                if (this->version >= 6U) {
+                    writer.write_u32(border.corner1_x);
+                    writer.write_u32(border.corner1_y);
+                }
+                writer.write_u32(border.x);
+                writer.write_u32(border.y);
+            }
+            writer.write_u32(this->width * this->height);
+            for (const auto elevation: this->elevations) {
+                if (this->version >= 5U) {
+                    writer.write_u16(elevation);
+                } else {
+                    writer.write_u8(static_cast<std::uint8_t>(elevation));
+                }
+            }
+            return writer.take();
+        }
+    };
+
+    /** The value type of an asset property. */
+    enum class property_type : std::uint8_t {
+        boolean = 0,
+        integer = 1,
+        real_number = 2,
+        ascii_string = 3,
+        unicode_string = 4,
+        unknown = 5,
+    };
+
+    /** The payload of an `asset_property`; the active alternative tracks `property_type`. */
+    using property_value = std::variant<bool, std::int32_t, float, std::string, std::u16string>;
+
+    /** One key/value pair carried by a map object or the world info. */
+    struct asset_property {
+        std::string name;
+        property_type type = property_type::integer;
+        property_value value{}; ///< bool, int32, float, ASCII/UTF-8 string, or UTF-16 string
+
+        [[nodiscard]] static auto boolean(std::string name, bool value) -> asset_property {
+            return {std::move(name), property_type::boolean, value};
+        }
+        [[nodiscard]] static auto integer(std::string name, std::int32_t value) -> asset_property {
+            return {std::move(name), property_type::integer, value};
+        }
+        [[nodiscard]] static auto real(std::string name, float value) -> asset_property {
+            return {std::move(name), property_type::real_number, value};
+        }
+        [[nodiscard]] static auto text(std::string name, std::string value) -> asset_property {
+            return {std::move(name), property_type::ascii_string, std::move(value)};
+        }
+        [[nodiscard]] static auto wide_text(std::string name, std::u16string value) -> asset_property {
+            return {std::move(name), property_type::unicode_string, std::move(value)};
+        }
+
+        [[nodiscard]] auto as_bool() const -> bool {
+            const auto *held = std::get_if<bool>(&this->value);
+            return held != nullptr && *held;
+        }
+        [[nodiscard]] auto as_int() const -> std::int32_t {
+            const auto *held = std::get_if<std::int32_t>(&this->value);
+            return held != nullptr ? *held : 0;
+        }
+        [[nodiscard]] auto as_real() const -> float {
+            const auto *held = std::get_if<float>(&this->value);
+            return held != nullptr ? *held : 0.0F;
+        }
+        [[nodiscard]] auto as_ascii() const -> std::string_view {
+            const auto *held = std::get_if<std::string>(&this->value);
+            return held != nullptr ? std::string_view{*held} : std::string_view{};
+        }
+        [[nodiscard]] auto as_unicode() const -> const std::u16string * { return std::get_if<std::u16string>(&this->value); }
+    };
+
+    /** One object placed on the map (building, prop, waypoint, ...). */
+    struct map_object {
+        std::string type_name; ///< the SAGE `ThingTemplate` name, e.g. `*Waypoints/Waypoint`
+        coord3d position;
+        float angle = 0.0F;
+        road_type road = road_type::none; ///< road connectivity flags (0 for most objects)
+        std::uint16_t version = 1;
+        std::vector<asset_property> properties;
+
+        [[nodiscard]] auto property(std::string_view key) const -> const asset_property * {
+            for (const auto &entry: this->properties) {
+                if (entry.name == key) return &entry;
+            }
+            return nullptr;
+        }
+    };
+
+    /** A player start position recovered from a `Player_N_Start` waypoint. */
+    struct player_start {
+        int index = 0; ///< the `N` in `Player_N_Start` (1-based)
+        coord3d position;
+    };
+
+    /** One `MPPositionInfo` entry. */
+    struct mp_position {
+        bool is_human = false;
+        bool is_computer = false;
+        bool load_ai_script = false;
+        std::uint32_t team = 0;
+        std::vector<std::string> side_restrictions;
+        std::uint16_t version = 1;
+    };
+
+    /** One `WaypointPath` (a link between two waypoints by id). */
+    struct waypoint_path {
+        std::int32_t start_id = 0;
+        std::int32_t end_id = 0;
+    };
+
+    namespace detail {
+        /** True when `data` begins with the ASCII tag (avoids `memcmp` with a literal). */
+        [[nodiscard]] inline auto starts_with(std::span<const std::byte> data, std::string_view tag) -> bool {
+            if (data.size() < tag.size()) return false;
+            for (std::size_t i = 0; i < tag.size(); ++i) {
+                if (std::to_integer<std::uint8_t>(data[i]) != static_cast<std::uint8_t>(tag[i])) return false;
+            }
+            return true;
+        }
+
+        [[nodiscard]] inline auto read_property(byte_reader &reader, const name_table &names) -> asset_property {
+            asset_property property;
+            property.type = static_cast<property_type>(reader.read_u8());
+            property.name = names.name(reader.read_u24());
+            switch (property.type) {
+            case property_type::boolean: property.value = reader.read_bool(); break;
+            case property_type::integer: property.value = reader.read_i32(); break;
+            case property_type::real_number: property.value = reader.read_f32(); break;
+            case property_type::ascii_string:
+            case property_type::unknown: property.value = reader.read_u16_prefixed_ascii(); break;
+            case property_type::unicode_string: property.value = reader.read_u16_prefixed_utf16(); break;
+            }
+            return property;
+        }
+
+        inline auto write_property(byte_writer &writer, const asset_property &property, name_table &names) -> void {
+            writer.write_u8(static_cast<std::uint8_t>(property.type));
+            writer.write_u24(names.get_or_create(property.name));
+            switch (property.type) {
+            case property_type::boolean: writer.write_bool(property.as_bool()); break;
+            case property_type::integer: writer.write_i32(property.as_int()); break;
+            case property_type::real_number: writer.write_f32(property.as_real()); break;
+            case property_type::ascii_string:
+            case property_type::unknown: writer.write_u16_prefixed_ascii(property.as_ascii()); break;
+            case property_type::unicode_string: {
+                const auto *text = property.as_unicode();
+                writer.write_u16_prefixed_utf16(text != nullptr ? *text : std::u16string{});
+                break;
+            }
+            }
+        }
+
+        [[nodiscard]] inline auto parse_property_list(byte_reader &reader, const name_table &names) -> std::vector<asset_property> {
+            const auto count = reader.read_u16();
+            std::vector<asset_property> properties;
+            properties.reserve(count);
+            for (std::uint16_t i = 0; i < count; ++i) properties.push_back(read_property(reader, names));
+            return properties;
+        }
+
+        inline auto write_property_list(byte_writer &writer, const std::vector<asset_property> &properties, name_table &names) -> void {
+            writer.write_u16(static_cast<std::uint16_t>(properties.size()));
+            for (const auto &property: properties) write_property(writer, property, names);
+        }
+
+        /** Split `Player_<n>_Start` into `n`, or 0 when the name does not match. */
+        [[nodiscard]] inline auto parse_player_start_name(std::string_view name) -> int {
+            constexpr std::string_view prefix = "Player_";
+            constexpr std::string_view suffix = "_Start";
+            if (!name.starts_with(prefix) || !name.ends_with(suffix)) return 0;
+            const auto digits = name.substr(prefix.size(), name.size() - prefix.size() - suffix.size());
+            if (digits.empty() || !std::ranges::all_of(digits, [](char ch) { return ch >= '0' && ch <= '9'; })) return 0;
+            return std::stoi(std::string{digits});
+        }
+    }
+
+    /**
+     * A parsed `.map`: the asset-name table plus the ordered chunk list.
+     */
+    class map_document {
+    public:
+        /** Unwrap (BIG payload / `EAR\0` / bare RefPack / bare `CkMp`) and parse. */
+        [[nodiscard]] static auto parse(std::span<const std::byte> file) -> map_document {
+            auto data = std::vector<std::byte>{file.begin(), file.end()};
+            if (is_refpack(data)) data = refpack_decompress(data); // a BIG payload
+            if (detail::starts_with(data, std::string_view{"EAR\0", 4})) {
+                const auto *body = reinterpret_cast<const std::byte *>(data.data()) + 8;
+                std::span<const std::byte> payload{body, data.size() - 8U};
+                data = maybe_decompress(payload);
+            } else if (is_refpack(data)) {
+                data = refpack_decompress(data);
+            }
+            return map_document::from_ckmp(data);
+        }
+
+        [[nodiscard]] static auto open(const std::filesystem::path &path) -> map_document {
+            return map_document::parse(read_file(path));
+        }
+
+        [[nodiscard]] auto names() const -> const name_table & { return this->names_; }
+        [[nodiscard]] auto names() -> name_table & { return this->names_; }
+        [[nodiscard]] auto chunks() const -> const std::vector<map_chunk> & { return this->chunks_; }
+        [[nodiscard]] auto chunks() -> std::vector<map_chunk> & { return this->chunks_; }
+
+        [[nodiscard]] auto find_chunk(std::string_view name) const -> const map_chunk * {
+            for (const auto &chunk: this->chunks_) {
+                if (chunk.name == name) return &chunk;
+            }
+            return nullptr;
+        }
+
+        [[nodiscard]] auto find_chunk(std::string_view name) -> map_chunk * {
+            for (auto &chunk: this->chunks_) {
+                if (chunk.name == name) return &chunk;
+            }
+            return nullptr;
+        }
+
+        [[nodiscard]] auto has_chunk(std::string_view name) const -> bool { return this->find_chunk(name) != nullptr; }
+
+        /** The chunk of a known kind, or `nullptr`. */
+        [[nodiscard]] auto find_chunk(chunk_kind kind) const -> const map_chunk * {
+            for (const auto &chunk: this->chunks_) {
+                if (chunk.kind == kind) return &chunk;
+            }
+            return nullptr;
+        }
+
+        [[nodiscard]] auto find_chunk(chunk_kind kind) -> map_chunk * {
+            for (auto &chunk: this->chunks_) {
+                if (chunk.kind == kind) return &chunk;
+            }
+            return nullptr;
+        }
+
+        [[nodiscard]] auto has_chunk(chunk_kind kind) const -> bool { return this->find_chunk(kind) != nullptr; }
+
+        // -- typed chunks ---------------------------------------------------
+
+        /** The terrain grid, or `std::nullopt` when the map has no `HeightMapData`. */
+        [[nodiscard]] auto height_map() const -> std::optional<height_map_data> {
+            const auto *chunk = this->find_chunk("HeightMapData");
+            if (chunk == nullptr) return std::nullopt;
+            return height_map_data::parse(chunk->version, chunk->payload);
+        }
+
+        /** Replace (or create) the `HeightMapData` chunk from a grid. */
+        auto set_height_map(height_map_data data) -> void {
+            auto *chunk = this->find_chunk("HeightMapData");
+            if (chunk == nullptr) {
+                chunk = &this->chunks_.emplace_back();
+                chunk->name = "HeightMapData";
+                chunk->kind = chunk_kind::height_map_data;
+                chunk->asset_index = this->names_.get_or_create("HeightMapData");
+                chunk->version = data.version;
+            } else {
+                data.version = chunk->version; // keep the file's on-disk version
+            }
+            chunk->payload = data.serialize();
+        }
+
+        /** Every object the map places. */
+        [[nodiscard]] auto objects() const -> std::vector<map_object> {
+            const auto *chunk = this->find_chunk("ObjectsList");
+            if (chunk == nullptr) return {};
+            return map_document::decode_objects(this->names_, chunk->payload);
+        }
+
+        /** Replace (or create) the `ObjectsList` chunk. */
+        auto set_objects(const std::vector<map_object> &objects) -> void {
+            auto *chunk = this->find_chunk("ObjectsList");
+            if (chunk == nullptr) {
+                chunk = &this->chunks_.emplace_back();
+                chunk->name = "ObjectsList";
+                chunk->kind = chunk_kind::objects_list;
+                chunk->asset_index = this->names_.get_or_create("ObjectsList");
+                chunk->version = 1;
+            }
+            chunk->payload = map_document::encode_objects(this->names_, objects);
+        }
+
+        /** The `Player_N_Start` waypoints, ordered by index. */
+        [[nodiscard]] auto player_starts() const -> std::vector<player_start> {
+            std::vector<player_start> starts;
+            for (const auto &object: this->objects()) {
+                if (object.type_name != "*Waypoints/Waypoint") continue;
+                const auto *name_property = object.property("waypointName");
+                if (name_property == nullptr) continue;
+                const auto index = detail::parse_player_start_name(name_property->as_ascii());
+                if (index == 0) continue;
+                starts.push_back({index, object.position});
+            }
+            std::ranges::sort(starts, {}, &player_start::index);
+            return starts;
+        }
+
+        [[nodiscard]] auto mp_positions() const -> std::vector<mp_position> {
+            const auto *chunk = this->find_chunk("MPPositionList");
+            if (chunk == nullptr) return {};
+            return map_document::decode_mp_positions(chunk->payload);
+        }
+
+        auto set_mp_positions(const std::vector<mp_position> &positions) -> void {
+            auto *chunk = this->find_chunk("MPPositionList");
+            if (chunk == nullptr) {
+                chunk = &this->chunks_.emplace_back();
+                chunk->name = "MPPositionList";
+                chunk->kind = chunk_kind::mp_position_list;
+                chunk->asset_index = this->names_.get_or_create("MPPositionList");
+                chunk->version = 1;
+            }
+            chunk->payload = map_document::encode_mp_positions(this->names_, positions);
+        }
+
+        /** The `WorldInfo` property list. */
+        [[nodiscard]] auto world_info() const -> std::vector<asset_property> {
+            const auto *chunk = this->find_chunk("WorldInfo");
+            if (chunk == nullptr) return {};
+            byte_reader reader{chunk->payload};
+            return detail::parse_property_list(reader, this->names_);
+        }
+
+        auto set_world_info(const std::vector<asset_property> &properties) -> void {
+            auto *chunk = this->find_chunk("WorldInfo");
+            if (chunk == nullptr) {
+                chunk = &this->chunks_.emplace_back();
+                chunk->name = "WorldInfo";
+                chunk->kind = chunk_kind::world_info;
+                chunk->asset_index = this->names_.get_or_create("WorldInfo");
+                chunk->version = 1;
+            }
+            byte_writer writer;
+            detail::write_property_list(writer, properties, this->names_);
+            chunk->payload = writer.take();
+        }
+
+        /** The waypoint paths (`WaypointsList`). */
+        [[nodiscard]] auto waypoint_paths() const -> std::vector<waypoint_path> {
+            const auto *chunk = this->find_chunk("WaypointsList");
+            if (chunk == nullptr) return {};
+            byte_reader reader{chunk->payload};
+            const auto count = reader.read_u32();
+            std::vector<waypoint_path> paths;
+            paths.reserve(count);
+            for (std::uint32_t i = 0; i < count; ++i) paths.push_back({reader.read_i32(), reader.read_i32()});
+            return paths;
+        }
+
+        // -- serialisation --------------------------------------------------
+
+        /** The bare `CkMp` byte image. */
+        [[nodiscard]] auto to_ckmp() const -> std::vector<std::byte> {
+            byte_writer writer;
+            writer.write_ascii("CkMp");
+            const auto count = static_cast<std::uint32_t>(this->names_.size());
+            writer.write_u32(count);
+            for (std::uint32_t i = count; i >= 1U; --i) {
+                const auto &name = this->names_.entries()[i];
+                writer.write_u8(static_cast<std::uint8_t>(name.size()));
+                writer.write_ascii(name);
+                writer.write_u32(i);
+            }
+            for (const auto &chunk: this->chunks_) {
+                writer.write_u32(chunk.asset_index);
+                writer.write_u16(chunk.version);
+                writer.write_u32(static_cast<std::uint32_t>(chunk.payload.size()));
+                writer.write_bytes(chunk.payload);
+            }
+            return writer.take();
+        }
+
+        /**
+         * A standalone `.map` image.
+         *
+         * When `compress` is true the result is `EAR\0` + `u32` decompressed size
+         * + a RefPack stream (the retail compression). When false it is a bare
+         * `CkMp` tree. To store a map inside a `BIG4`, pass the *uncompressed*
+         * image and let `big_writer::add(..., compress = true)` wrap it once.
+         */
+        [[nodiscard]] auto serialize(bool compress = false) const -> std::vector<std::byte> {
+            auto ckmp = this->to_ckmp();
+            if (!compress) return ckmp;
+            byte_writer writer;
+            writer.write_ascii(std::string_view{"EAR\0", 4});
+            writer.write_u32(static_cast<std::uint32_t>(ckmp.size()));
+            const auto packed = refpack_compress(ckmp);
+            writer.write_bytes(packed);
+            return writer.take();
+        }
+
+        /** True when the name table carries `name` (top-level chunk, property, ...). */
+        [[nodiscard]] auto has_name(std::string_view name) const -> bool {
+            for (std::uint32_t i = 1; i < this->names_.entries().size(); ++i) {
+                if (this->names_.entries()[i] == name) return true;
+            }
+            return false;
+        }
+
+    private:
+        map_document() = default;
+
+        [[nodiscard]] static auto from_ckmp(std::span<const std::byte> data) -> map_document {
+            if (data.size() < 8U || !detail::starts_with(data, "CkMp")) throw map_error("not a CkMp map");
+            byte_reader reader{data};
+            (void) reader.read_ascii(4);
+            const auto count = reader.read_u32();
+            map_document document;
+            document.names_.resize(count + 1U);
+            for (std::uint32_t i = count; i >= 1U; --i) {
+                const auto length = reader.read_u8();
+                auto name = reader.read_ascii(length);
+                const auto index = reader.read_u32();
+                if (index != i) throw map_error("asset name table index mismatch");
+                document.names_.set_name(i, std::move(name));
+            }
+            while (reader.remaining() >= 10U) {
+                const auto index = reader.read_u32();
+                const auto version = reader.read_u16();
+                const auto size = reader.read_u32();
+                if (index >= document.names_.entries().size() || reader.remaining() < size) throw map_error("truncated CkMp chunk");
+                map_chunk chunk;
+                chunk.asset_index = index;
+                chunk.name = std::string{document.names_.entries()[index]};
+                chunk.kind = chunk_kind_of(chunk.name);
+                chunk.version = version;
+                const auto payload = reader.read_bytes(size);
+                chunk.payload.assign(payload.begin(), payload.end());
+                document.chunks_.push_back(std::move(chunk));
+            }
+            return document;
+        }
+
+        [[nodiscard]] static auto decode_objects(const name_table &names, std::span<const std::byte> payload) -> std::vector<map_object> {
+            byte_reader reader{payload};
+            std::vector<map_object> objects;
+            while (reader.remaining() >= 10U) {
+                (void) reader.read_u32(); // nested asset index (always "Object")
+                const auto version = reader.read_u16();
+                const auto size = reader.read_u32();
+                if (reader.remaining() < size) throw map_error("truncated Object asset");
+                const auto body = reader.read_bytes(size);
+                byte_reader body_reader{body};
+                map_object object;
+                object.version = version;
+                object.position.x = body_reader.read_f32();
+                object.position.y = body_reader.read_f32();
+                object.position.z = body_reader.read_f32();
+                object.angle = body_reader.read_f32();
+                object.road = static_cast<road_type>(body_reader.read_u32());
+                object.type_name = body_reader.read_ascii(body_reader.read_u16());
+                object.properties = detail::parse_property_list(body_reader, names);
+                objects.push_back(std::move(object));
+            }
+            return objects;
+        }
+
+        [[nodiscard]] static auto encode_objects(name_table &names, const std::vector<map_object> &objects) -> std::vector<std::byte> {
+            const auto object_index = names.get_or_create("Object");
+            byte_writer writer;
+            for (const auto &object: objects) {
+                byte_writer body;
+                body.write_f32(object.position.x);
+                body.write_f32(object.position.y);
+                body.write_f32(object.position.z);
+                body.write_f32(object.angle);
+                body.write_u32(static_cast<std::uint32_t>(object.road));
+                body.write_u16(static_cast<std::uint16_t>(object.type_name.size()));
+                body.write_ascii(object.type_name);
+                detail::write_property_list(body, object.properties, names);
+                writer.write_u32(object_index);
+                writer.write_u16(object.version);
+                writer.write_u32(static_cast<std::uint32_t>(body.size()));
+                writer.write_bytes(body.data());
+            }
+            return writer.take();
+        }
+
+        [[nodiscard]] static auto decode_mp_positions(std::span<const std::byte> payload) -> std::vector<mp_position> {
+            byte_reader reader{payload};
+            std::vector<mp_position> positions;
+            while (reader.remaining() >= 10U) {
+                (void) reader.read_u32(); // nested asset index (always "MPPositionInfo")
+                const auto version = reader.read_u16();
+                const auto size = reader.read_u32();
+                if (reader.remaining() < size) throw map_error("truncated MPPositionInfo asset");
+                const auto body = reader.read_bytes(size);
+                byte_reader body_reader{body};
+                mp_position position;
+                position.version = version;
+                position.is_human = body_reader.read_bool();
+                position.is_computer = body_reader.read_bool();
+                if (version > 0U) position.load_ai_script = body_reader.read_bool();
+                position.team = body_reader.read_u32();
+                if (version > 0U) {
+                    const auto count = body_reader.read_u32();
+                    position.side_restrictions.reserve(count);
+                    for (std::uint32_t i = 0; i < count; ++i) position.side_restrictions.push_back(body_reader.read_u16_prefixed_ascii());
+                }
+                positions.push_back(std::move(position));
+            }
+            return positions;
+        }
+
+        [[nodiscard]] static auto encode_mp_positions(name_table &names, const std::vector<mp_position> &positions) -> std::vector<std::byte> {
+            const auto info_index = names.get_or_create("MPPositionInfo");
+            byte_writer writer;
+            for (const auto &position: positions) {
+                byte_writer body;
+                body.write_bool(position.is_human);
+                body.write_bool(position.is_computer);
+                if (position.version > 0U) body.write_bool(position.load_ai_script);
+                body.write_u32(position.team);
+                if (position.version > 0U) {
+                    body.write_u32(static_cast<std::uint32_t>(position.side_restrictions.size()));
+                    for (const auto &side: position.side_restrictions) body.write_u16_prefixed_ascii(side);
+                }
+                writer.write_u32(info_index);
+                writer.write_u16(position.version);
+                writer.write_u32(static_cast<std::uint32_t>(body.size()));
+                writer.write_bytes(body.data());
+            }
+            return writer.take();
+        }
+
+        name_table names_;
+        std::vector<map_chunk> chunks_;
+    };
+
+} // namespace ra3::assets

third_party/libra3assets/src/refpack.cppm

@@ -0,0 +1,284 @@
+/**
+ * EA's RefPack compression codec.
+ *
+ * Red Alert 3 compresses individual `BIG4` payloads and every SAGE `.map` with
+ * RefPack (the `10 FB` stream shared across EA titles). This partition decodes
+ * and encodes that stream. The decoder is a port of the reference used across
+ * the project (`ra3tools/ra3_big.py`, `OpenRA3`'s `ra3.fs`); the encoder is a
+ * greedy LZ77 matcher that emits only canonical tokens, so anything it produces
+ * is readable by the same decoder (and by the game).
+ */
+export module ra3.assets:refpack;
+
+import std;
+
+import :bytes;
+import :error;
+
+export namespace ra3::assets {
+
+    /** Max back-reference distance (the 17-bit RefPack window). */
+    inline constexpr std::size_t refpack_window = 1U << 17U;
+
+    /** True when `data` starts with a RefPack header (`0b??010000`, `0xFB`). */
+    [[nodiscard]] inline auto is_refpack(std::span<const std::byte> data) -> bool {
+        return data.size() >= 2U && (std::to_integer<std::uint8_t>(data[0]) & 0x3EU) == 0x10U && std::to_integer<std::uint8_t>(data[1]) == 0xFBU;
+    }
+
+    /** Read the declared output size from a RefPack header without decompressing. */
+    [[nodiscard]] inline auto refpack_output_size(std::span<const std::byte> data) -> std::uint32_t {
+        if (!is_refpack(data)) throw refpack_error("not a RefPack stream");
+        std::size_t pos = 0;
+        const auto header = std::to_integer<std::uint8_t>(data[pos++]);
+        const bool large_files = (header & 0x80U) != 0U;
+        const bool compressed_size_present = (header & 0x01U) != 0U;
+        pos++; // 0xFB
+        const std::size_t size_bytes = large_files ? 4U : 3U;
+        const auto read_size = [&]() -> std::uint32_t {
+            std::uint32_t value = 0;
+            for (std::size_t i = 0; i < size_bytes; ++i) {
+                if (pos >= data.size()) throw refpack_error("truncated RefPack size field");
+                value = (value << 8U) | std::to_integer<std::uint8_t>(data[pos++]);
+            }
+            return value;
+        };
+        if (compressed_size_present) (void) read_size();
+        return read_size();
+    }
+
+    /**
+     * Decompress an EA RefPack stream.
+     *
+     * @throws refpack_error if the stream is malformed or the length disagrees.
+     */
+    [[nodiscard]] inline auto refpack_decompress(std::span<const std::byte> data) -> std::vector<std::byte> {
+        if (!is_refpack(data)) throw refpack_error("not a RefPack stream");
+
+        std::size_t pos = 0;
+        const auto header = std::to_integer<std::uint8_t>(data[pos++]);
+        const bool large_files = (header & 0x80U) != 0U;
+        const bool compressed_size_present = (header & 0x01U) != 0U;
+        pos++; // 0xFB
+
+        const std::size_t size_bytes = large_files ? 4U : 3U;
+        const auto read_size = [&]() -> std::uint32_t {
+            std::uint32_t value = 0;
+            for (std::size_t i = 0; i < size_bytes; ++i) {
+                if (pos >= data.size()) throw refpack_error("truncated RefPack size field");
+                value = (value << 8U) | std::to_integer<std::uint8_t>(data[pos++]);
+            }
+            return value;
+        };
+
+        if (compressed_size_present) (void) read_size();
+        const auto out_len = read_size();
+
+        std::vector<std::byte> out;
+        out.reserve(out_len); // guarantees no reallocation, so overlapping reads stay valid
+
+        const auto copy_literals = [&](std::size_t count) {
+            if (pos + count > data.size()) throw refpack_error("truncated RefPack literals");
+            out.insert(out.end(), data.begin() + static_cast<std::ptrdiff_t>(pos), data.begin() + static_cast<std::ptrdiff_t>(pos + count));
+            pos += count;
+        };
+
+        // A back-reference may overlap its own output (an RLE run): out[start + i]
+        // is read one byte at a time, so the pattern repeats correctly.
+        const auto copy_reference = [&](std::size_t length, std::size_t distance) {
+            if (distance == 0U || distance > out.size()) throw refpack_error("RefPack back-reference out of range");
+            const auto start = out.size() - distance;
+            if (out.size() + length > out_len) throw refpack_error("RefPack output overrun");
+            for (std::size_t i = 0; i < length; ++i) out.push_back(out[start + i]);
+        };
+
+        while (pos < data.size()) {
+            const auto cmd = std::to_integer<std::uint8_t>(data[pos++]);
+            if ((cmd & 0x80U) == 0U) { // 2-byte command
+                if (pos >= data.size()) throw refpack_error("truncated 2-byte command");
+                const auto b2 = std::to_integer<std::uint8_t>(data[pos++]);
+                copy_literals(cmd & 0x03U);
+                copy_reference(((cmd & 0x1CU) >> 2U) + 3U, ((cmd & 0x60U) << 3U) + b2 + 1U);
+            } else if ((cmd & 0x40U) == 0U) { // 3-byte command
+                if (pos + 1U >= data.size()) throw refpack_error("truncated 3-byte command");
+                const auto b2 = std::to_integer<std::uint8_t>(data[pos]);
+                const auto b3 = std::to_integer<std::uint8_t>(data[pos + 1U]);
+                pos += 2U;
+                copy_literals((b2 & 0xC0U) >> 6U);
+                copy_reference((cmd & 0x3FU) + 4U, ((b2 & 0x3FU) << 8U) + b3 + 1U);
+            } else if ((cmd & 0x20U) == 0U) { // 4-byte command
+                if (pos + 2U >= data.size()) throw refpack_error("truncated 4-byte command");
+                const auto b2 = std::to_integer<std::uint8_t>(data[pos]);
+                const auto b3 = std::to_integer<std::uint8_t>(data[pos + 1U]);
+                const auto b4 = std::to_integer<std::uint8_t>(data[pos + 2U]);
+                pos += 3U;
+                copy_literals(cmd & 0x03U);
+                copy_reference(((cmd & 0x0CU) << 6U) + b4 + 5U, ((cmd & 0x10U) << 12U) + (static_cast<std::size_t>(b2) << 8U) + b3 + 1U);
+            } else if (cmd < 0xFCU) { // long literal run
+                copy_literals((static_cast<std::size_t>(cmd & 0x1FU) + 1U) << 2U);
+            } else { // stop
+                copy_literals(cmd & 0x03U);
+                break;
+            }
+        }
+
+        if (out.size() != out_len) throw refpack_error("RefPack length mismatch");
+        return out;
+    }
+
+    /** Decompress `data` when it is RefPack, otherwise copy it unchanged. */
+    [[nodiscard]] inline auto maybe_decompress(std::span<const std::byte> data) -> std::vector<std::byte> {
+        if (is_refpack(data)) return refpack_decompress(data);
+        return {data.begin(), data.end()};
+    }
+
+    namespace detail {
+        /** True when `(length, distance)` maps to one of the three canonical tokens. */
+        [[nodiscard]] inline constexpr auto refpack_match_encodable(std::size_t length, std::size_t distance) -> bool {
+            if (length >= 3U && length <= 10U && distance >= 1U && distance <= 1024U) return true;
+            if (length >= 4U && length <= 67U && distance >= 1U && distance <= 16384U) return true;
+            if (length >= 5U && length <= 1028U && distance >= 1U && distance <= 131072U) return true;
+            return false;
+        }
+
+        /** Greedy RefPack encoder state. */
+        class refpack_encoder {
+        public:
+            explicit refpack_encoder(std::span<const std::byte> input)
+                : input_(input), chain_(input.size(), -1) {
+            }
+
+            [[nodiscard]] auto run() -> std::vector<std::byte> {
+                const auto n = this->input_.size();
+                const bool large = n >= (1U << 24U);
+                this->out_.write_u8(static_cast<std::uint8_t>(0x10U | (large ? 0x80U : 0x00U)));
+                this->out_.write_u8(0xFBU);
+                const std::size_t size_bytes = large ? 4U : 3U;
+                for (std::size_t i = size_bytes; i-- > 0U;) this->out_.write_u8(static_cast<std::uint8_t>((n >> (8U * i)) & 0xFFU));
+
+                std::size_t pos = 0;
+                std::size_t literals_start = 0;
+                while (pos < n) {
+                    std::size_t best_len = 0;
+                    std::size_t best_dist = 0;
+                    if (pos + 2U < n) this->find_match(pos, best_len, best_dist);
+                    if (best_len >= 3U) {
+                        const auto pending = pos - literals_start;
+                        const auto carry = pending % 4U;      // 0..3 literals ride with the token
+                        const auto run = pending - carry;     // always a multiple of 4
+                        this->emit_literal_run(literals_start, run);
+                        this->emit_match(literals_start + run, carry, best_len, best_dist);
+                        for (std::size_t i = pos; i < pos + best_len; ++i) this->insert(i);
+                        pos += best_len;
+                        literals_start = pos;
+                    } else {
+                        this->insert(pos);
+                        ++pos;
+                    }
+                }
+
+                const auto pending = n - literals_start;
+                const auto carry = pending % 4U;
+                this->emit_literal_run(literals_start, pending - carry);
+                this->out_.write_u8(static_cast<std::uint8_t>(0xFCU | carry));
+                this->write_literals(literals_start + (pending - carry), carry);
+                return this->out_.take();
+            }
+
+        private:
+            void insert(std::size_t pos) {
+                if (pos + 2U >= this->input_.size()) return;
+                const auto bucket = this->hash3(pos);
+                this->chain_[pos] = this->head_[bucket];
+                this->head_[bucket] = static_cast<std::int32_t>(pos);
+            }
+
+            void find_match(std::size_t pos, std::size_t &best_len, std::size_t &best_dist) const {
+                const auto n = this->input_.size();
+                const auto max_len = std::min<std::size_t>(1028U, n - pos);
+                auto candidate = this->head_[this->hash3(pos)];
+                int depth = 0;
+                while (candidate >= 0 && depth < 64) {
+                    const auto c = static_cast<std::size_t>(candidate);
+                    const auto distance = pos - c;
+                    if (distance > refpack_window) break; // the chain only walks backwards
+                    std::size_t length = 0;
+                    while (length < max_len && this->input_[c + length] == this->input_[pos + length]) ++length;
+                    if (length > best_len && refpack_match_encodable(length, distance)) {
+                        best_len = length;
+                        best_dist = distance;
+                        if (length == max_len) break;
+                    }
+                    candidate = this->chain_[c];
+                    ++depth;
+                }
+            }
+
+            void emit_literal_run(std::size_t offset, std::size_t count) {
+                std::size_t remaining = count;
+                std::size_t at = offset;
+                while (remaining >= 4U) {
+                    std::size_t step = std::min<std::size_t>(112U, remaining);
+                    step -= step % 4U;
+                    if (step < 4U) step = 4U;
+                    this->out_.write_u8(static_cast<std::uint8_t>(0xE0U | ((step / 4U) - 1U)));
+                    this->write_literals(at, step);
+                    at += step;
+                    remaining -= step;
+                }
+            }
+
+            void emit_match(std::size_t literal_offset, std::size_t literal_count, std::size_t length, std::size_t distance) {
+                const auto d = static_cast<std::uint32_t>(distance - 1U);
+                if (length >= 3U && length <= 10U && distance <= 1024U) { // 2-byte token
+                    const auto cmd = static_cast<std::uint8_t>((((d >> 8U) & 0x03U) << 5U) | (static_cast<std::uint32_t>(length - 3U) << 2U) |
+                                                               static_cast<std::uint32_t>(literal_count));
+                    this->out_.write_u8(cmd);
+                    this->out_.write_u8(static_cast<std::uint8_t>(d & 0xFFU));
+                } else if (length >= 4U && length <= 67U && distance <= 16384U) { // 3-byte token
+                    this->out_.write_u8(static_cast<std::uint8_t>(0x80U | (length - 4U)));
+                    this->out_.write_u8(static_cast<std::uint8_t>((literal_count << 6U) | ((d >> 8U) & 0x3FU)));
+                    this->out_.write_u8(static_cast<std::uint8_t>(d & 0xFFU));
+                } else if (length >= 5U && length <= 1028U && distance <= 131072U) { // 4-byte token
+                    const auto l = static_cast<std::uint32_t>(length - 5U);
+                    const auto cmd = static_cast<std::uint8_t>(0xC0U | (((l >> 8U) & 0x03U) << 2U) | ((d >> 12U) & 0x10U) |
+                                                                       static_cast<std::uint32_t>(literal_count));
+                    this->out_.write_u8(cmd);
+                    this->out_.write_u8(static_cast<std::uint8_t>((d >> 8U) & 0xFFU));
+                    this->out_.write_u8(static_cast<std::uint8_t>(d & 0xFFU));
+                    this->out_.write_u8(static_cast<std::uint8_t>(l & 0xFFU));
+                } else {
+                    throw refpack_error("internal error: unencodable RefPack match");
+                }
+                this->write_literals(literal_offset, literal_count);
+            }
+
+            void write_literals(std::size_t offset, std::size_t count) {
+                for (std::size_t i = 0; i < count; ++i) this->out_.write_u8(std::to_integer<std::uint8_t>(this->input_[offset + i]));
+            }
+
+            [[nodiscard]] auto hash3(std::size_t pos) const -> std::size_t {
+                const auto a = static_cast<std::uint32_t>(std::to_integer<std::uint8_t>(this->input_[pos]));
+                const auto b = static_cast<std::uint32_t>(std::to_integer<std::uint8_t>(this->input_[pos + 1U]));
+                const auto c = static_cast<std::uint32_t>(std::to_integer<std::uint8_t>(this->input_[pos + 2U]));
+                return ((a | (b << 8U) | (c << 16U)) * 2654435761U) >> (32U - 16U);
+            }
+
+            std::span<const std::byte> input_;
+            std::vector<std::int32_t> chain_;
+            std::vector<std::int32_t> head_ = std::vector<std::int32_t>(1U << 16U, -1);
+            byte_writer out_;
+        };
+    }
+
+    /**
+     * Compress a byte range into a canonical RefPack stream.
+     *
+     * The encoder is a plain greedy LZ77: it never emits a token form the
+     * decoder above cannot read, so `refpack_decompress(refpack_compress(x))`
+     * is lossless for every input.
+     */
+    [[nodiscard]] inline auto refpack_compress(std::span<const std::byte> input) -> std::vector<std::byte> {
+        return detail::refpack_encoder{input}.run();
+    }
+
+} // namespace ra3::assets

third_party/libra3assets/tests/test_assets.cpp

@@ -0,0 +1,310 @@
+#include "test_main.hpp"
+
+import std;
+import ra3.assets;
+
+using namespace ra3::assets;
+
+namespace {
+
+    auto bytes_of(std::string_view text) -> std::vector<std::byte> {
+        std::vector<std::byte> out;
+        out.reserve(text.size());
+        for (const auto ch: text) out.push_back(static_cast<std::byte>(static_cast<unsigned char>(ch)));
+        return out;
+    }
+
+    auto text_of(std::span<const std::byte> bytes) -> std::string {
+        return std::string{reinterpret_cast<const char *>(bytes.data()), bytes.size()};
+    }
+
+    /** A deterministic pseudo-random buffer (no external RNG needed). */
+    auto pseudo_random(std::size_t size, std::uint32_t seed) -> std::vector<std::byte> {
+        std::vector<std::byte> out;
+        out.reserve(size);
+        std::uint32_t state = seed;
+        for (std::size_t i = 0; i < size; ++i) {
+            state = state * 1664525U + 1013904223U;
+            out.push_back(static_cast<std::byte>((state >> 16U) & 0xFFU));
+        }
+        return out;
+    }
+
+    auto make_empty_ckmp(const std::vector<std::string> &names) -> std::vector<std::byte> {
+        byte_writer writer;
+        writer.write_ascii("CkMp");
+        writer.write_u32(static_cast<std::uint32_t>(names.size()));
+        for (std::uint32_t i = static_cast<std::uint32_t>(names.size()); i >= 1U; --i) {
+            writer.write_u8(static_cast<std::uint8_t>(names[i - 1].size()));
+            writer.write_ascii(names[i - 1]);
+            writer.write_u32(i);
+        }
+        return writer.take();
+    }
+
+    auto make_csf() -> std::vector<std::byte> {
+        byte_writer writer;
+        writer.write_ascii(" FSC");
+        writer.write_u32(3);
+        writer.write_u32(2); // labels
+        writer.write_u32(2); // value blocks
+        writer.write_u32(0);
+        writer.write_u32(0);
+        writer.write_u32(csf_label_flag);
+        writer.write_u32(1);
+        writer.write_u32(3);
+        writer.write_ascii("ABC");
+        writer.write_u32(csf_value_flag);
+        writer.write_u32(5);
+        for (const auto ch: std::string_view{"Hello"}) writer.write_u16(static_cast<std::uint16_t>(ch) ^ 0xFFFFU);
+        writer.write_u32(csf_label_flag);
+        writer.write_u32(1);
+        writer.write_u32(3);
+        writer.write_ascii("UNI");
+        writer.write_u32(csf_value_flag);
+        writer.write_u32(1);
+        writer.write_u16(0x4E2DU ^ 0xFFFFU); // U+4E2D (CJK)
+        return writer.take();
+    }
+
+} // namespace
+
+TEST(refpack_roundtrip_small) {
+    const std::vector<std::string> samples{"", "A", "AB", "ABC", "ABCD", "abcabcabc", std::string(300, 'z')};
+    for (const auto &sample: samples) {
+        const auto input = bytes_of(sample);
+        const auto packed = refpack_compress(input);
+        const auto restored = refpack_decompress(packed);
+        CHECK_EQ(restored.size(), input.size());
+        CHECK(std::ranges::equal(restored, input));
+    }
+}
+
+TEST(refpack_roundtrip_large_and_repetitive) {
+    std::vector<std::byte> input;
+    for (int i = 0; i < 2000; ++i) {
+        for (const auto ch: std::string_view{"lorem ipsum dolor sit amet "}) input.push_back(static_cast<std::byte>(ch));
+    }
+    const auto random = pseudo_random(50000, 0x1234ABCDU);
+    input.insert(input.end(), random.begin(), random.end());
+    const auto packed = refpack_compress(input);
+    CHECK(packed.size() < input.size()); // the repeated prefix must compress
+    CHECK(std::ranges::equal(refpack_decompress(packed), input));
+}
+
+TEST(refpack_decode_known_stream) {
+    // "abcd" literals, then a back-reference (distance 4, length 3) -> "abcdabc".
+    const std::vector<std::byte> stream{
+        std::byte{0x10}, std::byte{0xFB}, std::byte{0x00}, std::byte{0x00}, std::byte{0x07}, std::byte{0xE0},
+        std::byte{'a'},  std::byte{'b'},  std::byte{'c'},  std::byte{'d'},  std::byte{0x00}, std::byte{0x03},
+        std::byte{0xFC},
+    };
+    CHECK(is_refpack(stream));
+    CHECK_EQ(text_of(refpack_decompress(stream)), "abcdabc");
+    CHECK_EQ(refpack_output_size(stream), 7U);
+}
+
+TEST(big_roundtrip) {
+    big_writer writer;
+    writer.add("data\\a.txt", bytes_of("hello world"));
+    writer.add("data\\b.bin", bytes_of(std::string(1000, 'x')), true);
+    const auto image = writer.write();
+
+    CHECK(image.size() >= 16U);
+    const std::string magic{reinterpret_cast<const char *>(image.data()), 4};
+    CHECK_EQ(magic, "BIG4");
+
+    const auto archive = big_archive::from_bytes(image);
+    CHECK_EQ(archive.size(), 2U);
+    CHECK(archive.contains("data\\a.txt"));
+    CHECK_EQ(text_of(archive.read("data\\a.txt")), "hello world");
+    CHECK_EQ(archive.read("data\\b.bin").size(), 1000U);
+    CHECK_EQ(archive.find("data\\").size(), 2U);
+    // The first payload starts 64-byte aligned, as the retail archives do.
+    CHECK_EQ(archive.entries()[0].offset % 64U, 0U);
+}
+
+TEST(big_open_from_disk_is_lazy) {
+    big_writer writer;
+    writer.add("data\\a.txt", bytes_of("hello disk"));
+    writer.add("data\\b.bin", bytes_of(std::string(4096, 'q')), true);
+    const auto image = writer.write();
+
+    const auto path = std::filesystem::temp_directory_path() / "libra3assets_big_lazy.big";
+    write_file(path, image);
+
+    const auto archive = big_archive::open(path);
+    CHECK_EQ(archive.size(), 2U);
+    CHECK(archive.path() == path);
+    CHECK(archive.contains("data\\a.txt"));
+    CHECK_EQ(archive.entries()[0].offset % 64U, 0U);
+    CHECK_EQ(text_of(archive.read("data\\a.txt")), "hello disk");
+    CHECK_EQ(archive.read("data\\b.bin").size(), 4096U);
+    CHECK_EQ(text_of(archive.read_prefix("data\\a.txt", 5)), "hello");
+    CHECK(archive.read_prefix("data\\b.bin", 8U).size() == 8U);
+    std::error_code ec;
+    std::filesystem::remove(path, ec);
+}
+
+TEST(binary_manifest_and_hash) {
+    CHECK_EQ(hash_string("W3DMesh"), 0xC2B1A262U);
+    CHECK_EQ(hash_string("ABAIRFIELD", false), 0x2B479BD3U);
+    CHECK(hash_string("Texture") != hash_string("Texture", false));
+
+    const std::string name = "W3DMesh:TEST";
+    const std::string source = "art:test.w3x";
+    byte_writer manifest;
+    manifest.write_u8(0);  // not big-endian
+    manifest.write_u8(0);  // not linked
+    manifest.write_u16(5); // version
+    manifest.write_u32(0); // checksum
+    manifest.write_u32(0); // all-types hash
+    manifest.write_u32(1); // count
+    manifest.write_u32(12);
+    manifest.write_u32(0);
+    manifest.write_u32(0);
+    manifest.write_u32(0);
+    manifest.write_u32(0); // reference buffer
+    manifest.write_u32(0); // reference-name buffer
+    manifest.write_u32(static_cast<std::uint32_t>(name.size() + 1));
+    manifest.write_u32(static_cast<std::uint32_t>(source.size() + 1));
+    manifest.write_u32(hash_string("W3DMesh"));
+    manifest.write_u32(hash_string("TEST", false));
+    manifest.write_u32(hash_string("W3DMesh"));
+    manifest.write_u32(hash_string("TEST", false));
+    manifest.write_i32(0); // reference offset
+    manifest.write_i32(0); // reference count
+    manifest.write_i32(0); // name offset
+    manifest.write_i32(0); // source offset
+    manifest.write_u32(8); // instance size
+    manifest.write_u32(0); // relocation size
+    manifest.write_u32(0); // imports size
+    manifest.write_u32(0); // tokenized
+    manifest.write_ascii(name);
+    manifest.write_u8(0);
+    manifest.write_ascii(source);
+    manifest.write_u8(0);
+
+    byte_writer data;
+    data.write_u32(0); // stream checksum
+    data.write_ascii("PAYLOAD!");
+
+    auto container = binary_container::from_bytes(manifest.take(), data.take());
+    CHECK_EQ(container.size(), 1U);
+    const auto &asset = container.assets()[0];
+    CHECK_EQ(asset.name, "W3DMesh:TEST");
+    CHECK_EQ(asset.type_name(), "W3DMesh");
+    CHECK_EQ(asset.instance_name(), "TEST");
+    CHECK_EQ(asset.source, "art:test.w3x");
+    CHECK_EQ(text_of(container.read_instance(asset)), "PAYLOAD!");
+    CHECK_EQ(container.find("#0").name, "W3DMesh:TEST");
+    CHECK_EQ(container.of_type("w3dmesh").size(), 1U);
+    CHECK_EQ(container.type_counts().at("W3DMesh"), 1U);
+    CHECK(container.read_relocation(asset).empty());
+
+    container.set_cdata_source([&asset](const std::string &cdata_name) -> std::optional<std::vector<std::byte>> {
+        if (cdata_name == asset.cdata_name("static")) return bytes_of("CDATA");
+        return std::nullopt;
+    });
+    CHECK(container.read_cdata(asset).has_value());
+    CHECK_EQ(text_of(container.read_payload(asset)), "CDATA");
+}
+
+TEST(csf_roundtrip) {
+    auto table = csf_table::parse(make_csf());
+    CHECK_EQ(table.size(), 2U);
+    CHECK_EQ(table.version(), 3U);
+    CHECK_EQ(table.lookup("abc"), "Hello");      // lookup is case-insensitive
+    CHECK_EQ(table.lookup("ABC"), "Hello");
+    CHECK_EQ(table.lookup("uni"), "\xE4\xB8\xAD");
+    CHECK(table.find("missing") == nullptr);
+
+    const auto rewritten = table.write();
+    const auto reparsed = csf_table::parse(rewritten);
+    CHECK_EQ(reparsed.size(), 2U);
+    CHECK_EQ(reparsed.lookup("abc"), "Hello");
+    CHECK_EQ(reparsed.lookup("uni"), "\xE4\xB8\xAD");
+}
+
+TEST(csf_decode_utf16_surrogate) {
+    const std::u16string emoji = u"\U0001F600";
+    CHECK_EQ(utf16_to_utf8(emoji), "\xF0\x9F\x98\x80");
+}
+
+TEST(map_roundtrip) {
+    const std::vector<std::string> names{"HeightMapData", "ObjectsList", "Object", "waypointName", "MPPositionList", "MPPositionInfo", "WorldInfo", "waypointID"};
+    auto document = map_document::parse(make_empty_ckmp(names));
+    CHECK_EQ(document.names().size(), names.size());
+
+    height_map_data height;
+    height.width = 2;
+    height.height = 2;
+    height.version = 6;
+    height.elevations = {1, 2, 3, 4};
+    document.set_height_map(height);
+
+    map_object waypoint;
+    waypoint.type_name = "*Waypoints/Waypoint";
+    waypoint.position = {100.0F, 200.0F, 0.0F};
+    waypoint.properties.push_back(asset_property::text("waypointName", "Player_1_Start"));
+    waypoint.properties.push_back(asset_property::integer("waypointID", 0));
+    document.set_objects({waypoint});
+
+    mp_position position;
+    position.is_human = true;
+    position.team = 1;
+    document.set_mp_positions({position});
+
+    const auto ckmp = document.to_ckmp();
+    const auto reparsed = map_document::parse(ckmp);
+
+    CHECK(reparsed.has_chunk(chunk_kind::height_map_data));
+    CHECK(reparsed.has_chunk(chunk_kind::objects_list));
+    CHECK(reparsed.has_chunk(chunk_kind::mp_position_list));
+    CHECK_EQ(reparsed.find_chunk("HeightMapData")->kind, chunk_kind::height_map_data);
+    CHECK_EQ(chunk_kind_of("BlendTileData"), chunk_kind::blend_tile_data);
+    CHECK_EQ(chunk_kind_of("NotAChunk"), chunk_kind::unknown);
+
+    const auto restored = reparsed.height_map();
+    CHECK(restored.has_value());
+    CHECK_EQ(restored->width, 2U);
+    CHECK_EQ(restored->at(1, 1), 4U);
+    CHECK_EQ(restored->vertical_scale(), 0.0390625F);
+
+    const auto objects = reparsed.objects();
+    CHECK_EQ(objects.size(), 1U);
+    CHECK_EQ(objects[0].type_name, "*Waypoints/Waypoint");
+    CHECK_EQ(objects[0].property("waypointID")->as_int(), 0);
+
+    const auto starts = reparsed.player_starts();
+    CHECK_EQ(starts.size(), 1U);
+    CHECK_EQ(starts[0].index, 1);
+    CHECK_EQ(starts[0].position.x, 100.0F);
+
+    const auto positions = reparsed.mp_positions();
+    CHECK_EQ(positions.size(), 1U);
+    CHECK(positions[0].is_human);
+    CHECK_EQ(positions[0].team, 1U);
+}
+
+TEST(map_compressed_and_big_payload) {
+    const std::vector<std::string> names{"HeightMapData"};
+    auto document = map_document::parse(make_empty_ckmp(names));
+    height_map_data height;
+    height.width = 1;
+    height.height = 1;
+    height.version = 6;
+    height.elevations = {7};
+    document.set_height_map(height);
+
+    // EAR\0 + RefPack round-trip.
+    const auto compressed = document.serialize(true);
+    const auto from_compressed = map_document::parse(compressed);
+    CHECK(from_compressed.height_map().has_value());
+    CHECK_EQ(from_compressed.height_map()->at(0, 0), 7U);
+
+    // A BIG payload is one more RefPack layer over the map file.
+    const auto big_payload = refpack_compress(document.to_ckmp());
+    const auto from_big = map_document::parse(big_payload);
+    CHECK_EQ(from_big.height_map()->at(0, 0), 7U);
+}

third_party/libra3assets/tests/test_main.cpp

@@ -0,0 +1,5 @@
+#include "test_main.hpp"
+
+int main() {
+    return ra3test::run_all();
+}

third_party/libra3assets/tests/test_main.hpp

@@ -0,0 +1,83 @@
+#ifndef RA3TEST_HPP
+#define RA3TEST_HPP
+
+// A tiny dependency-free test harness (registry + CHECK macros). Each unit-test
+// executable compiles test_main.cpp and links the sources under test.
+
+#include <functional>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <vector>
+
+namespace ra3test {
+
+    struct test_case {
+        std::string name;
+        std::function<void()> fn;
+    };
+
+    inline auto registry() -> std::vector<test_case> & {
+        static std::vector<test_case> tests;
+        return tests;
+    }
+
+    inline auto failure_count() -> int & {
+        static int count = 0;
+        return count;
+    }
+
+    struct registrar {
+        registrar(std::string name, std::function<void()> fn) { registry().push_back({std::move(name), std::move(fn)}); }
+    };
+
+    inline auto report_failure(const std::string &expr, const std::string &file, int line) -> void {
+        ++failure_count();
+        std::cerr << "  FAIL " << file << ':' << line << "  " << expr << '\n';
+    }
+
+    inline auto check(bool condition, const std::string &expr, const std::string &file, int line) -> void {
+        if (!condition) report_failure(expr, file, line);
+    }
+
+    inline auto run_all() -> int {
+        int passed = 0;
+        for (auto &test: registry()) {
+            const int before = failure_count();
+            std::cout << "[ RUN  ] " << test.name << '\n';
+            try {
+                test.fn();
+            } catch (const std::exception &exc) {
+                report_failure(std::string("uncaught exception: ") + exc.what(), __FILE__, __LINE__);
+            }
+            if (failure_count() == before) {
+                ++passed;
+                std::cout << "[  OK  ] " << test.name << '\n';
+            }
+        }
+        std::cout << "\n" << passed << '/' << registry().size() << " tests passed, " << failure_count() << " failure(s)\n";
+        return failure_count() == 0 ? 0 : 1;
+    }
+
+} // namespace ra3test
+
+#define TEST(name)                                                                                                     \
+    static void name();                                                                                                \
+    static ::ra3test::registrar ra3test_reg_##name(#name, name);                                                       \
+    static void name()
+
+#define CHECK(cond) ::ra3test::check((cond), #cond, __FILE__, __LINE__)
+#define CHECK_EQ(a, b) ::ra3test::check_eq((a), (b), #a, #b, __FILE__, __LINE__)
+
+namespace ra3test {
+    template<typename A, typename B>
+    auto check_eq(const A &a, const B &b, const std::string &ea, const std::string &eb, const std::string &file, int line) -> void {
+        if (!(a == b)) {
+            std::ostringstream os;
+            os << ea << " == " << eb;
+            report_failure(os.str(), file, line);
+        }
+    }
+}
+
+#endif // RA3TEST_HPP