Collisions

• Simulation may be interrupted by a collision.
• A collision force should be generated to reflect the momentum of the colliding masses.
• Using fixed time step, collision may be detected via interpenetration.
• May be necessary to use a shorter than the frame time and/or back up the simulation after interpenetration to handle collisions reasonably robustly.
• collision checks between O(n) objects

  Partition space, hierarchies, etc.

• Elastic vs inelastic