after following ya'lls advice, i came up with this: http://oi45.tinypic.com/2qd03rr.jpg i'm diggin it, but i did something a little different: instead of just inverting a few faces, i inverted all of them. when i inverted only a few, the ones i inverted only showed up on the collision model, so i did all of them instead, and it worked. if i did that for other maps, would it still work? (note, i didn't separate the model into separate groups for this, could that effect the collision model as well?)