Command & Conquer Generals Zero Hour native Linux port

I'm attempting to create a native Linux port of Zero Hour. I suspect that it's a fool's errand, but it should be an interesting project.

You can learn a lot by reading source code, but you can learn a lot more by trying to get that code working using a different compiler on a different operating system.

Progress so far

I've added some progress screenshots to the wiki page.

• Displays a window with the splash screen.
• Plays the logo movie.
• Displays the main menu.
• The credits menu works (including the music!)
• The options menu mostly works (the IP address stuff doesn't, because I haven't implemented the network code yet. Also the resolution picker needs work... see below).
• I have added the skeleton of an OpenGL renderer, which is a prerequisite to doing any 3D rendering.
• I have made a start on rendering the "shell map" (the 3D scene that plays behind the main menu). New screenshot in the wiki.
• The scripted camera fly around of the shell map works, though the camera parameters are not quite right yet.
• The DynamicMemoryAllocator works.
• Subsystems implemented:
  • TheNameKeyGenerator
  • TheCommandList
  • TheFileSystem
  • TheLocalFileSystem
  • TheArchiveFileSystem
  • TheWritableGlobalData
  • TheGameLODManager
  • TheGameText
  • TheScienceStore
  • TheMultiplayerSettings
  • TheTerrainTypes
  • TheTerrainRoads
  • TheGlobalLanguageData
  • TheAudio
  • TheFunctionLexicon
  • TheModuleFactory (62 out of 218 modules implemented)
  • TheParticleSystemManager (minimal)
  • TheMessageStream
  • TheSidesList
  • TheCaveSystem
  • TheRankInfoStore
  • ThePlayerTemplateStore
  • TheFXListStore
  • TheWeaponStore
  • TheObjectCreationListStore
  • TheLocomotorStore
  • TheSpecialPowerStore
  • TheDamageFXStore
  • TheArmorStore
  • TheBuildAssistant
  • TheThingFactory
  • TheUpgradeCenter
  • TheGameClient (partial)
    • TheDrawGroupInfo
    • TheDisplayStringManager
    • TheDisplay
    • TheKeyboard
    • TheMouse
    • TheMappedImageCollection
    • TheAnim2DCollection
    • TheFontLibrary
    • TheHeaderTemplateManager
    • TheTerrainVisual
    • TheWindowManager
    • TheVideoPlayer
    • TheLanguageFilter
    • TheCampaignManager
    • TheEva
    • TheIMEManager
    • TheShell
    • TheInGameUI
      • TheControlBar (partial)
  • TheAI
  • TheGameLogic (partial)
    • ThePartitionManager
    • TheTerrainLogic
    • TheScriptEngine
  • TheTeamFactory
  • TheCrateSystem
  • ThePlayerList
  • TheRecorder
  • TheRadar
  • TheVictoryConditions
  • TheActionManager
  • TheGameState
  • TheMapCache

Still to do

• The main-menu screen needs tweaking. The transparency is a bit off. The exit dialog shows transparency problems too.
• Menu transparency is fixed. I had to set a blend mode for the alpha channel to work.
• Most of the main-menu buttons don't work yet.
• 2D sound works, music works, but I don't have an SDL library for 3D (positional) sound. I may have to look at OpenAL.
• Lots more work to do to improve the shell map scene.
• Everything else.

Dependencies

I'm using SDL3, SDL_ttf 3 (fonts), and SDL_sound (decoding .mp3 files), so you'll have to install those libraries.

I'm using FFmpeg to replace Bink, so I installed libavformat-dev, libswscale-dev, and libavdevice-dev.

You need to create a symlink called assets in the GeneralsMD directory that points to the directory where you have Zero Hour installed, such that typing ls assets/AudioZH.big should work. At the moment it's used to load the splash screen, but eventually it will be used to load all of the assets.

Compiling

I'm using a standard makefile. Open a terminal in the GeneralsMD/Code directory, and type make, or make DEBUG=1 for a debug build.

The compiled executable is GeneralsMD/Run/rts.

Running

You can type make run to run the executable.

If you get an error message that says:

ERROR: Could not load bitmap: Couldn't open ../assets/Install_Final.bmp: No such file or directory

then you forgot to create the symlink mentioned above.

Use the Exit button in the main menu to exit the game.

What I've learned so far

My professional programming experience is in corporate systems, not games, so I was interested so see how a commercial game was put together. Zero Hour seems like a good case study because, while it relies on a number of third-party libraries, it doesn't use a separate game engine.

Screen resolutions

The game's preferred resolution is 800 x 600, because that's the resolution of the 2d assets. Because of this, the resolution picker in the Options menu filters to show only 4-by-3 aspect ratio resolutions, to avoid image stretching.

However, when I use SDL_GetFullscreenDisplayModes, and filter to only 4-by-3 resolutions, the only two I get are 800 x 600, and 1024 x 768! If I turn off the filter then I get my monitor's native resolution (2560 x 1440) as well. What about all of the resolutions in between?

Looking in "NVIDIA X Server Settings", I see the following additional resolutions: 1280 x 720, 1280 x 800, 1280 x 1024, 1366 x 768, 1440 x 900, 1600 x 1200, 1680 x 1050, 1920 x 1080, and 1920 x 1200. However, those resolutions are marked as "scaled". I assume that when I choose one of those resolutions the monitor remains at 2560 x 1440, but the pixels are scaled in software (CPU? GPU?) to make them fit.

I may have to do the same for Zero Hour: add in some extra resolutions and scale them in software. In particular, I'd like to add 1600 x 1200, as that would give a clean (and easy) 2x scaling of the assets.