I’ve been working on collision detection and I think my previous optimism from having worked on this stuff a pretty good bit before was well founded.  So far I have implemented the simplest case of collision detection from this paper.  So with a single triangle and a sphere moving around in space the sphere stops at the surface of the triangle no matter how it is oriented.  The sphere doesn’t react to the collision, it just stops.  It also doesn’t work if the sphere hits an edge or vertex of the triangle.  I just haven’t implemented that part yet.  Still, it’s exciting to have this much done.  The paper describes using ellipsoid space so that a single ellipsoid can represent a humanoid character.  This is fine but I think I would rather use two equally sized spheres, one at the top of the capsule representing the player, and one at the bottom.  This may require twice the checks, but I also don’t have to worry about world space versus ellipsoid space.  In any case, I’m going to get sphere-mesh collisions working correctly, then I’ll decide whether to use ellipsoids or two spheres.  I’ll have a demo of basic collision detection up soon.