   Player movement collision
  I am creating an FPS game and I have been researching different player collision techniques but I was hoping someone could give me ideas on what some good tricks are. I was thinking of doing just an AABB, which I may do to start with. The player can jump though, so I suppose I would need to do an aabb check that has a velocity to a triangle check.The other thing I was reading was using a cylinder for the player, since that should deal with all rotations (where an AABB would not). This seems like it would be expensive though.Does anyone have any ideas on something I could do?   
  Cylinders are a bit tricky computationally. Boxes are relatively easy, but tend to 'snag' on things due to their sharp corners. There is no need to have the box rotate with the player. Usually the box is an AABB, big enough to take into account the player rotations. Another solution is the ellipse / sphere method. See Kasper Fauerby's paper on the matter. For spheres, your player can be made of a collection of sphere, usually only 3 or 4 will suffice.However, player / player collisions, I'd use AABBs for more decisive collisions. There is no reason why you can't use various collision shapes depending on the objects you are testing against (vehicles vs players : convex hulls vs aabb, vehicle vs world : spheres vs triangles, player vs player : abb vs aabb, player vs world : spheres vs triangles, ect...).in any case, you would need to tweak player physics regardless of the collision shape, for example to allow the player to walk over small debris, to walk downstairs (instead of just tumbling down), to walk up stairs, all the context senitive stuff like hang on ledges, hide behind wall, ect...   