Friction and Restitution

Materials are owned by the PxPhysics object and can be shared among objects in multiple scenes. The material properties of two objects involved in a collision may be combined in various ways. See the reference documentation for PxMaterial for more details.

PhysX objects the collision geometry of which is a triangle mesh or a heightfield (see Shapes) can have one material per triangle.

Friction uses the coulomb friction model which is based on the concept of 2 coefficients: the static friction coefficient and the dynamic friction coefficient (sometimes called kinetic friction). The friction resists the relative lateral motion of two solid surfaces in contact. These two coefficients define a relationship between the normal force exerted by each surface on the other and the amount of friction force that is applied to resist lateral motion. The static friction defines the amount of friction that is applied between surfaces that are not moving lateral to each other. The dynamic friction defines the amount of friction applied between surfaces that are moving relative to each other.

The coefficient of restitution of two colliding objects is a fractional value that represents the ratio of speeds after and before an impact, taken along the line of impact. A coefficient of restitution of 1 is said to collide elastically, while a coefficient of restitution < 1 is said to be inelastic.