v0.1.0: software map renderer + SDL3 window viewer

README.md

@@ -20,8 +20,8 @@ Ghidra.
 OpenRA3 is at **v0.0.1**. The engine compiles and runs headless, and a **minimal
 skirmish** is playable: it reads a real multiplayer map out of your install,
 recovers the player start waypoints, and simulates two sides earning credits,
-training units and fighting until one base falls. There is no renderer yet, so
-the match is observed as a deterministic headless result.
+training units and fighting until one base falls. The map and match state can be
+**rendered** to a window (SDL3) or to an image.
 
 ```text
 $ openra3 skirmish --game-dir "/game" --map map_mp_2_feasel4
@@ -66,6 +66,8 @@ built-in test map so the project still builds and runs in CI.
 | `src/fs/ra3.fs.cppm` | `BIG4` archives, RefPack codec, local install locator |
 | `src/map/ra3.map.cppm` | map catalog, `EAR`/RefPack unwrap, start waypoints |
 | `src/skirmish/ra3.skirmish.cppm` | units, economy, AI, combat, win condition |
+| `src/render/ra3.render.cppm` | ARGB framebuffer, TGA decode, BMP encode, map compositing |
+| `src/ui/ra3.ui.*.cppm` | SDL3 window viewer (null backend when SDL3 is absent) |
 | `src/ra3.cppm` | umbrella module re-exporting the SDK |
 | `apps/openra3/main.cpp` | `maps` / `skirmish` CLI |
 | `tests/ra3_tests.cpp` | smoke tests (run via `ctest`) |
@@ -103,6 +105,32 @@ docker run --rm -v "/path/to/Red Alert 3:/game:ro" openra3-dev:local \
 `--frames N` caps the simulation length (default 15 minutes of game time at
 30 Hz). The result is deterministic for a given map and seed.
 
+## Rendering the map
+
+The renderer draws the map's own overview art, a world grid and the match state
+(start markers in yellow, player 0 in blue, player 1 in red).
+
+**Offscreen image** (works anywhere, no display needed):
+
+```bash
+docker run --rm -v "/path/to/Red Alert 3:/game:ro" -v "$PWD/out:/out" openra3-dev:local \
+    /work/build/bin/openra3 render --game-dir /game --map map_mp_2_feasel4 --out /out/map.bmp
+```
+
+**Interactive window** (SDL3; drag to pan, wheel to zoom, Esc to quit). In a
+container you need an X server on the host — on Windows run
+[VcXsrv](https://sourceforge.net/projects/vcxsrv/) and launch it with "Disable
+access control", then:
+
+```bash
+docker run --rm -v "/path/to/Red Alert 3:/game:ro" -e DISPLAY=host.docker.internal:0.0 \
+    openra3-dev:local /work/build/bin/openra3 render --game-dir /game --map map_mp_2_feasel4
+```
+
+If no display is available the viewer falls back to writing `openra3_view.bmp`.
+The unit overlay uses an approximate world scale (`--world-size`, default
+5120); exact calibration from the map's heightmap is on the roadmap.
+
 ## Reverse engineering
 
 The reconstruction is driven by Ghidra against the retail binary. See