The values for the Surface Properties on the Rigid Body property page for each collision object are multiplied by the values of the corresponding parameters set for other collision objects. That means that the results of a collision are modulated by the elasticity and friction of all colliding rigid bodies.
To keep this relationship simple, it's usually best to set the values for only one collision object at a time and test out the results.
For details on these parameters, see Surface Properties [Properties Reference].
Elasticity, also called the coefficient of restitution, is the factor that influences the amount of energy that is retained to move rigid bodies in the opposite direction (bounce) during a collision. For example, a billiard ball has very low elasticity properties so when it hits a table, hardly any kinetic energy is retained.
A value of 0 means that a rigid body will not bounce in a collision; a value of 1 means that the rigid body will not lose any energy and therefore bounce back with a speed equal and opposite to what it had before the collision.
Remember that using values above 1 make the rigid body actually return more energy at each collision. As well, using high values for elasticity can make a simulation less stable.
Friction is the resistive force acting between colliding rigid bodies that tends to oppose and dampen motion. For example, a billiard ball rolling along a table has a lower friction value than a rubber ball would. Likewise, a billiard ball rolling on a carpet would encounter more friction than if it was rolling on a marble floor.
Friction can be either static or dynamic. In general, static friction is greater than dynamic friction.
Static friction is the resistive force that opposes a rigid body from changing its state from resting to motion when in contact with another rigid body. For instance, if you place a ball on an sloped plane, the static friction determines how easily the ball begins its initial slide or roll down the plane. Static friction has little or no effect after an object is moving.
Dynamic (also known as kinetic) friction is how much a moving rigid body resists movement against another rigid body's surface. This is the force that tends to slow down a rigid body in motion. This force is generally proportional to any force that has been applied to the rigid body, so you can think of it as the ratio of frictional force to the applied force on the rigid body.
Except where otherwise noted, this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License
