You can move the object emitter around with the mouse and change the direction by clicking on the pointed end. This is what I consider a production version since I've inlined a few things. I have a more academic version that is a little easier to read. The whole thing is also dumbed down a little to make the math a little easier. How it works: When a ball encounters a collision object it uses the [ point towards[ Collision ] ] command block and then uses sin and cos to calculate a colliion normal. That normal is used to calculate a resulting velocity perpendicular to the surface and velocity tangent to the surface. Friction and restitution are applied to make the ball bounce.
