MapSizeExt

A Syringe-injected DLL for Command & Conquer: Red Alert 2 — Yuri's Revenge that raises the engine's hardcoded 512-cell map grid so you can play maps larger than the vanilla limit. It works alongside Ares/Antares + Phobos.

Status

Stride 1024 — up to 512×512 maps — fully playable. Confirmed in-game (temperate cliff map + generated 300×300 / 500×500): rendering and lighting, deploy/build, pathfinding including slopes and naval, harvester auto-mine, shroud/fog reveal, walls, the minimap/radar, and AI base-building all work.

This is the first public milestone. Bigger square maps (past ~500×500) are blocked by a separate engine limit — see Limits — which is the next thing being worked on.

Install

You need a working YR install that already runs Syringe-injected DLLs (e.g. the CnCNet client with Ares/Antares + Phobos).

1. Copy MapSizeExt.dll and MAPSIZEEXT.INI into your YR game directory (the folder with gamemd-spawn.exe).
2. Make Syringe inject it — add -i=MapSizeExt.dll to the Syringe command line, next to the existing -i=Ares.dll/-i=Antares.dll and -i=Phobos.dll:
   • Windows: ExtraCommandLineParams in the client's ClientDefinitions.ini.
   • Linux/Wine (CnCNet): the wine Syringe.exe -i=… gamemd-spawn.exe line in Resources/Compatibility/Unix/wine-game.sh.
   • The CnCNet client only injects DLLs that carry a .syhks00 section — this one does, so on some clients simply placing it is enough. Fully restart the client after installing.
3. Drop a large map into Maps/Custom/ (a sample 500×500 map ships with this release), then start a skirmish/LAN game on it.

Verify it loaded

Open MapSizeExt.log in the game directory. You should see:

MapSizeExt v0.3 (init in-game via DllMain)
Stride       = 1024
Total        = 1048576
...
[stride] 436 sites, shift 0x09 -> 0x0A (stride 1024)

No log = Syringe didn't inject the DLL (check step 2).

Configuration — MAPSIZEEXT.INI

[MapSize]
Stride=1024        ; cell-grid row stride (power of two). 512 = vanilla no-op.
MaxDimension=1024  ; per-axis map size gate (replaces the engine's cmp ax,512)
MaxWidth=512
MaxHeight=512

• Stride=512 makes the whole DLL a no-op (vanilla behaviour) — useful to confirm it loads before enabling.
• Stride=1024 → maps up to 512×512 (the tested milestone).
• The [Debug] section exposes per-patch-group toggles for bisecting problems without a rebuild; leave them at their defaults unless you're debugging.

Limits

• W + H ≤ Stride. At Stride=1024 that's a max square of ~512×512.
• The engine's base-1000 cell-number format caps square maps at ~500×500, independent of stride: waypoints/terrain/units are packed as Y*1000 + X, and the isometric cell coordinate runs up to W+H−1, so W+H must stay ≤ ~1000. Raising the stride does not lift this — it's the next milestone.
• 32-bit engine. gamemd is not Large-Address-Aware (2 GB ceiling); very large maps are memory-heavy. A full 512×512 map is comfortable.
• You still need a map actually built at the larger size (a normal editor won't create them). The companion generator RA2MapGen produces test maps.

Build

MSVC via GitHub Actions (the .syhks00 Syringe section requires the MSVC toolchain). Push to the repo and Actions builds MapSizeExt.dll, or run the build.yml workflow manually. YRpp headers live in YRpp/.

How it works (short version)

The engine addresses cells as Cells[Y*512 + X], with 512 baked in as shl reg,9 in hundreds of sites plus assorted add reg,0x200 row-walks, byte-offset iterators, bounds cmp eax,0x40000, coordinate masks, the IsoMapPack5 decode buffer, radar surfaces, and the subzone/pathfinding grid. MapSizeExt reads Stride from the INI and rewrites all of those to log2(stride) at load time (a strict no-op at 512), and installs a handful of trampoline hooks for the cases that can't be a plain immediate rewrite (dim gates, garbage-cell guards, the coord-transform crash guard). It also runtime- patches the inlined 512-stride in Antares.dll and Phobos.dll, since those compile the cell index in too. See src/Patches.cpp and src/Hooks.cpp.

Credits

Built with YRpp and Syringe. Cross-referenced against CCHyper's Vinifera map-size work (Tiberian Sun, same engine family) and a parallel YR map-512 effort by Krisztiaan.

License

MapSizeExt is free software, licensed under the GNU General Public License v3.0 (see LICENSE). Copyleft: you may use, modify, and redistribute it, but derivative works must stay under the GPLv3 and keep their source available.