This article covers a lot of technology including: HDR effects, level-of-detail, stencil-buffer shadows, motion blur, collision detection, inverse kinematics, and fur rendering. A very, very good read.
It’s rare to see a detailed technical article like this from such a high profile game developer on the web. I strongly recommend that all the games/graphics programmers reading this check it out.
Update: It’s interesting to note that the main character is modelled as a sphere for collision detection.