I know for a fact that both Knights games use directx, because I own them both. If you look at the Jedi Knight II official site you will see that it uses DirectX as well. Jedi Knight I'm not sure of as there are multiple games that use that name. One of them is Dark Forces II which I also own and know uses DirectX. The other is Jedi Academy (another game that I own) and it does use DirectX. http://support.lucasarts.com/tsg/SWKotORIIQuestions/Video%20Issues/OpenGLCompatibility.htm "To run Star Wars Knights of the Old Republic II: The Sith Lords, your video card driver must be using OpenGL 1.4 compatible software. OpenGL is a graphics API (Application Programming Interface) that was originally developed for professional workstations. It is now a standard API for 3D hardware acceleration, utilized in several current 3D games for the PC." As for the Jedi Knight I & II , both games are built on the Quake3 Team Arena game engine... an OpenGL product like everything else programmed by John Carmack. Also for clarification. OpenGL is graphics only, there is a similar project for audio known as OpenAL. DirectX is used for both graphic and audio programming. JKI&II use OpenGL graphics, and use DirectX for audio.