Quake3 Raytraced is a project to, well, re-write the graphics renderer from Quake3 to use a raytracing engine.
The game engine was written from scratch and supports player and bot movement including shooting and jumping, collision detection, and many sepcial effects like jump-pads and teleporters.
As you can see on the screenshots page some things aren't as detailed as in the original version, however the raytracing allows some very cool effects!