The Quake engine is the game engine developed by id Software to power their 1996 video game Quake. It featured true 3D real-time rendering and is now licensed under the terms of GNU General Public License v2.0 or later. After release, it immediately forked, as did the level design. Much of the engine remained in Quake II and Quake III Arena. The Quake engine, like the Doom engine, used binary space partitioning (BSP) to optimise the world rendering. The Quake engine also used Gouraud shading for moving objects, and a static lightmap for nonmoving objects.