Commercial Tools

Several low-cost game engines are available. Qube provides a free Windows binary and charges for Mac and console versions of their engine. Terathon. Cipher costs only $100, with source code. Garage Games and Unity run on both Windows and MacOSX and offer indie licenses. PTK is free for freeware games.

RenderWare has been absorbed by EA, but Gamebryo is still around.

Unity has a web player, as does Virtools. The Shockwave player also has an embedded physics engine and so can be used for web-based 3D games.

The aforementioned engines focus on graphics, and you need more than graphics to run a game. Simple collision detection and physics simulation is doable on your own, but anything complex is best left to middleware. Hence the popularity of physics engines such as Havok and Ageia.

Game engines for mobile phones include X-Forge, Mophun, Mascot Capsule, and Superscape

Other middleware includes RAD Game Tools, CRI Middleware. Simbionics and Pathengine provide AI middleware.

Software engineers and GUI designers with experience in other domains might wonder why they have to invent their own user interface systems from scratch. Anark and ScaleForm offer user interface toolkits for games.

Middleware for network games includes Quazal and SecurePlay.

Vendors who cater specifically to the DOD game community include Mak Technologies, (network middleware for distributed interactive simulation), Boston Dynamics (human simulation), and Multigen (content creation).

Mod Kits

If you can't afford the huge license fees for the complete game engines from Epic, id, Crytek, and Lithtech, you can still use those engines by creating game mods. For Half Life, check out the VERC Collective. CryEngine mods are discussed on Cry Mod. Mods and information about modding Unreal can be found at Planet Unreal. The official Unreal Developer Network and the unofficial Unreal Wiki also have information on UnrealScript. Third-party tools script editing tools include WOTgreal, an inexpensive UnrealScript IDE, and UnCodeX, an open-source UnrealScript class/code browser and documentation generator. The Atari Community and 3D Buzz host forums on Unreal modding.

Open Source

If you're ready to dig into some code, there are plenty of open-source games out there - bzflag, TORCS, Flight Gear, LGames, Macdoku and Open Frag. ScummVM runs the LucasArts adventure games.

For card games, check out Cards, Poker Source and Poker3D.

Open source 3D engines include Genesis3D, Ogre, NeoEngine, Yakes, and Irrlicht. Delta3D is developed at the MOVES Institute.

The Open Dynamics Engine, the Tokamak Physics Engine and Bullet are open source physics engines. Open Steer is a C++ library for steering behavior. The Newton Game Dynamics SDK is available for free.

PaperVision3D and Sandy provide 3D Actionscript libraries. APE is an Actionscript 2D physics engine. Open Source Flash lists other open-source Flash projects.