Hey guys; I am new to the forums. I am an effects artist who's working a Rigid Body Dynamics project and I may be able to use some of you guys' expertise while I'm building these simulations. As I stated above, I'm doing R&D for a deformation system I'm working on. What I want to do is to take the speed and mechanical properties of a projectile and calculate the displacement (wether permanent or elastic) of an object upon contact with this projectile. I"m basically new to building rigid body solvers from scratch, but essentially what I want to do is to be able to define what kind of material an object is (concrete, rubber, copper, brass, Glass etc.) and have it react appropriately to the projectile. (Wether it stretches, tears or fractures) If you guys have any books/material that you can point me to, basically concepts that will be essential for me to learn, I would be grateful. In addition to this, I have a question to start with. If a bullet is penetrating a material at a defined velocity and from a defined distance, what mechanical properties of the material decides how deep the bullet penetrates before stopping. (if it does indeed stop and not go straight through) Say we define all the variables involved, is there a formula to calculate this 'drag force' or whatever force it is that controls how quick the bullet comes to a stop?