id Tech 2

id Tech 2, formerly known as the Quake II engine is a game engine developed by id Software for use in their games, most notably Quake II. Since its release, id Tech 2 has been licensed for use in several other games. One of the engine's most notable features was out-of-the-box support for hardware-accelerated graphics, specifically OpenGL, along with the traditional software renderer.Another interesting feature was the subdivision of some of the components into dynamic-link libraries. This allowed both software and OpenGL renderers, which were switched between by loading and unloading separate libraries.Libraries were also used for the game logic, for two reasons: The level format, as with previous id Software engines, used BSP. The levels were lit through a lightmap method, in which light data for each surface is precalculated (this time, via a radiosity method) and stored as an image in the level file, which is then used to determine how much lighting intensity each model should... full article at wikipedia