id Tech 3, popularly known as the Quake III Arena engine, is a game engine developed by id Software for their video game Quake III Arena. It has been adopted by numerous games.
At QuakeCon 2005, John Carmack announced that the id Tech 3 source code would be released under the GNU General Public License (version 2), and it was released on August 19, 2005. The code can be downloaded from id's GitHub account.
ioquake3 is a game engine project which aims to build upon the id Tech 3 source code release in order to remove bugs, clean up source code and to add more advanced graphical and audio features via SDL and OpenAL. ioquake3 is also intended to act as a clean base package, upon which other projects may be built. The game engine supports Ogg Vorbis format and video capture of demos in .avi format.
The project was started shortly after the source code release with the goal of creating a bug-free, enhanced open source Quake III engine source code distribution upon which new games and projects can be based. In addition, the project aims to provide an improved environment in which Quake III: Arena, the Team Arena expansion pack and all the popular mods can be played.Notable features added by the project include builtin VoIP support, Anaglyph stereo rendering (for viewing with 3D glasses), and numerous security fixes. A full list of features is available on the project's website.