Terrain in Games

Computer games have featured terrain since the earliest 3D graphics.  However, representing the real world has not been a priority; they are usually "fantasy" worlds.  Even when the real world is the subject, an extremely limited area or view of the world is used, with no geographic framework.  Even worse, technology is usually created for a game and discarded or lost soon after.  Nonetheless, because so much time, energy and money has been spent in the game world over the years, it is worth looking at their terrain.

Middleware

• There is a field of software which is licensed to companies which want to produce a game.  This software includes APIs, tools, viewers, etc.  Sometime it is called a "game engine", or "middleware platform".
• Well-known examples include NDL Gamebryo, RenderWare, and the Quake and Unreal engine.
• There are also some mature open-source middleware systems such as Crystal Space and OGRE.
• Most of these include significant terrain capability.
• Outerra is a good example of a modern (2012) small commercial middleware focusing on terrain. "Planetary engine for seamless planet rendering from space down to the surface. Can use arbitrary resolution of elevation data, refining it to centimeter resolution using fractal algorithms. Unlimited visibility, progressive download of data, procedural content generation."

If we consider all game-oriented software libraries with terrain features, there are far too many to list (thousands?), and new ones appear very often.  Here are some historical examples:

• AdVantage terrain library by Filip Strugar
  • Very smooth paging of grid and imagery datasets up to 32k*32k in size
  • Fast rendering technique that uses almost no CPU time, is GPU and VRAM friendly, and has smooth transition (morph) between LOD levels.
  • Several nice demo datasets.
  • The author gives an example of elevation data size: For the classic Puget Sound dataset (16k*16k, 2 bytes/heixel), that's 256 Mh/512 MB of input, processed as 48.26 million triangles, 306 MB of storage space, which is only 1.2 bytes per input heixel.  Textures are handled as DDS with around .5 bytes/texel.
• T-5 Terrain Rendering Engine by Rui Ferreira
  • the current engine has attractive, full-unique texturing and RTIN CLOD for elevation
  • Rui says he tried out every sort of algorithm: binary triangle trees, quadtrees, split-only versions, leaf split-mergers, weird split metrics, vertices buffers, dynamic variance, diamond combiners, fan optimizers, 5 point strips, top-down, bottom-up...
  • the engine does full unique texturing

Unity

• In some cases is can be possible to get real-world data into a game engine, but the process is usually painfully difficult, as demonstrated in 3dNemo Tutorials: Google Earth to Unity (2009)
• As of 2013, the only way to get real terrain in/out of Unity is with scripts that must run inside Unity itself (Object2Terrain to import, TerrainObjExporter to export) or using unitless "raw" files.

See also: Terrain LOD: Regular-Grid Engines

See also: Traditional implementation of terrain in games (1995-2002)

Back in 2004, an approach which didn't take off: Using Game Engines for Architectural Walkthroughs.