id Tech

The id Tech engines up through 4.5 have been released as free software under the GNU General Public License.

However id Tech 4 had far fewer licensees than the Unreal Engine from Epic Games.

The source code to Wolfenstein 3D, along with its prequel Spear of Destiny, was released on 21 July 1995 under a proprietary license, and then later under GPL-2.0-or-later.

Other games using this engine are: Blake Stone: Aliens of Gold, Blake Stone: Planet Strike, Corridor 7: Alien Invasion, Operation Body Count, and, with several modifications, Rise of the Triad.

It featured true 3D real-time rendering and is the first id Tech engine to use the client–server model.

id Tech 2 was later updated for the release of Quake II in 1997, with enhancements such as colored lighting and a new MD2 model format.

The Quake III Arena engine was updated to patch 1.26 and later versions are called "Quake III Team Arena engine" with a new MD4 skeletal model format and huge outdoor areas.

id Tech 3 was updated with the 2001 release of Return to Castle Wolfenstein, which included a single-player scripting system.

id Tech 3 was also used to power the first Call of Duty title in 2003, ultimately spawning the IW engine.

During development, it was initially just a complete rewrite of the engine's renderer, while still retaining other subsystems, such as file access, and memory management.

[9] The engine was later used to power MachineGames' first two Wolfenstein titles, The New Order in 2014 and its standalone expansion The Old Blood, from 2015.

Development of the renderer is led by Tiago Sousa, who had previously worked on CryEngine, following previous technical director John Carmack's resignation in 2013. id Tech 6 was also used in Wolfenstein II: The New Colossus (2017), and Wolfenstein: Youngblood (2019) again by MachineGames.

The new engine is capable of delivering an increase in geometric detail without drops in frame-rate vs. id Tech 6.