id Tech is a series of separate game engines designed and developed by id Software. Prior to the presentation of the id Tech 5-based game Rage, the engines lacked official designation and as such were simply referred to as the Doom and Quake engines, from the name of the main game series the engines have been developed for. "id Tech" numbers 2, 3, and 4 have been released as free software under the GNU General Public License, along with the source code to Wolfenstein 3D, Doom and Quake.
According to Eurogamer.net, "id Software has been synonymous with PC game engines since the concept of a detached game engine was first popularised." However id Tech 4 had far fewer licensees than the Unreal Engine from Epic Games, and id planned to regain the momentum with id Tech 5, until they were bought by ZeniMax Media which intends to keep the id Tech engines exclusively for id's sister studios.
id Software had developed 3D engines for several games before Doom. Each game's engine had progressively more advanced 3D technology.
- Hovertank 3D (1991) used solid-color drawn walls and scalable sprites.
- Catacomb 3-D (1991) added texture mapping to the walls.
- Wolfenstein 3D (1992) increased the color palette from 16-color EGA to 256-color VGA. The game engine was also licensed out to other companies.
- Shadowcaster (1993) features diminished lighting, texture mapped floors and ceilings, walls with variable heights and sloped floors.
The Doom engine powers the id Software games Doom and Doom II. It was created by John Carmack, with auxiliary functions written by Mike Abrash, John Romero, Dave Taylor and Paul Radek. Originally developed on NeXT computers, it was ported to MS-DOS for Doom's initial release and was later ported to several game consoles and operating systems. The code was reused for several other titles: Heretic and Hexen (by Raven Software) and Strife (Rogue Software).
id Tech 2
Previously known as the "Quake engine" or "Quake II engine", and originally written to power 1996's Quake, written by id Software. It featured true 3D real-time rendering and is the first id engine to use the client–server model.
The Quake engine was updated with a new executable titled QuakeWorld that contained code to enhance the networking capabilities of Quake in response to the demand for across-internet network games that arose as a result of Quake's usage of UDP for networking. It was later updated again for Quake II with enhancements such as colored lighting and a new model format.
id Tech 3
Previously known as the "Quake III engine", it was derived from id Tech 2, although a large portion of code is new or re-written.
id Tech 4
Formerly the "Doom 3 engine", originally based on id Tech 3. It has a C++ based engine framework, and a new renderer, AI framework, physics engine, gameplay trigger system, and sound framework.
id Tech 5
This is the engine being used for id Software's new games.
The engine is not based on any previous id Tech engines, however it reuses much of the technology from the most updated id Tech 4 engine, including MegaTexture technology, parallax mapping, bloom, motion blur, soft particles, soft shadows and pixel shader effects. id is requiring companies that use the engine to publish their games through id's sister company, Bethesda Softworks.
id Tech 6
id Tech 6 is an upcoming OpenGL-based game engine under preliminary development by id Software, which will tentatively follow id Tech 5 for id Software games following Rage and Doom 4. It will work by raycasting the geometry represented by voxels (instead of triangles) stored in an octree.
- Tom Bramwell. "id Tech 5 : Steve Nix on the growth of id's next engine]". eurogamer.net.
- "Shadowcaster at Ravensoft.com". Raven Software. Retrieved 2009-07-02.
- Archived id Tech2 page mentioning Hexen II and QuakeWorld as examples of the engine, and referring to the "QUAKE and QUAKE II sections" of their technology download page.
- John Olick (2008). "Current Generation Parallelism In Games". id Software.