[2] 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.

This allowed both software and OpenGL renderers, which were selected by loading and unloading separate libraries.

Libraries were also used for the game logic, with consequences including: The level format, as with previous id Software engines, used binary space partitioning.

The level environments were lit using lightmaps, a method in which light data for each surface is precalculated (this time, via a radiosity method) and stored as an image, which is then used to determine the lighting intensity each 3D model should receive, but not its direction.

[5][6] id Software released the source code on December 22, 2001, under the terms of the GNU General Public License v2.0 or later.