OK. I have make a very curvy pipe and a ball slide in it from up to down (ball=physic-movement). There are two small parallel curve lines , thats are the borders of the pipe that the ball can not go outside when slide in it. The problem is, that when i use the polygon-box for colliosion in the pipe i need hundreds of points (or my other bad way: hundreds of small invisible solid objects on the border-pipe-line. Can i change the configuration that the ball collide with the pixels of the border-line ( I have Cutting the pipe in "side left" and "side right" with empty space in the middle for the ball. Thats my plan. How i can make this?