Just tried the OS X version. I just love blowing toruses* into their component polygons!

* Yes, toruses.

In the case of left4dead, the Zombie (almost certainly) has a bounding sphere It's not really relevant to the discussion, but Left 4 Dead uses a collection of bounding boxes for each zombie: one for the head, one or two for the torso, ones for upper arms and forearms, and thighs and calves, and han...