John D. Carmack II is an American computer programmer, video game developer and engineer. He co-founded the video game company id Software and was the lead programmer of its 1990s games Commander Keen, Wolfenstein 3D, Doom, Quake, and their sequels. Carmack made innovations in 3D computer graphics, such as his Carmack's Reverse algorithm for shadow volumes. In 2013, he resigned from id to work full-time at Oculus VR, where he served as CTO and later Consulting CTO in 2019. Carmack is a well-known advocate of open-source software, and has repeatedly voiced his opposition to software patents, equating them to robbery. He has also contributed to open-source projects, such as starting the initial port of the X Window System to Mac OS X Server and working to improve the OpenGL drivers for Linux through the Utah GLX project.