Have something never lose momentum?

I stumbled upon a similar problem ([here][1]). You can solve that in several ways.

• The totally-physic one : use a non-kinematic rigidbody and in FixedUpdate set the velocity to a constant magnitude (not direction mind you !)

• The half way : Use a kinematic rigidbody and move it in FixedUpdate. You can use OnColliderEnter to know when a collider was hit (you'll need a non-kinematic rigidbody on it) and then use Reflect on the direction to make the ball bounce.

• The not-physic-at-all way. Done in Update, it uses Translate (or position +=), Reflect and a way to know when the ball isn't where it should. I used Plane and [GetSide][2].

Good luck ! [1]: http://answers.unity3d.com/questions/205803/bouncing-objects-and-energy-loss.html [2]: http://unity3d.com/support/documentation/ScriptReference/Plane.GetSide.html