I have an ideea for a game but I can't figure exactly how to make make the hard part.

The hard part is, The game is 2D,and it would have a terrain texture. That terrain texture will be cut, so it will appear like there are hills.But the problem is,I have to cut that texture and display it forever,because I want to make a sidescroller. (so the hills will be procedurally generated in realtime)

Cutting the texture wouldn't be such a problem,what worries me are the physics.If I were to somehow write a function to find the points at the edge of every hill and make a shape for collision detection,that might take just too much time,given the fact that the terrain has to be cut TOO,before doing that.

forgot to say,the game would be for android,so I don't have PC resources.

And how should I cut the texture? Should I just check if the height of each pixel is bigger than the height of the generated point's?