To my experience, Player and objects "physiscShape" by default. Cheetah still uses a custom "ground repeller" code which you could most likely port to Bullet if you wanted. For something more detailed you will probably need physical constraints, which are not currently implemented. (but it's really a matter of hooking them from Bullet really) Can anyone correct me? This is what i concluded a couple months ago when i was bashing my head on it (before giving up).