unity-physicscore2d-materials

Set friction and bounciness through the surfaceMaterial field of PhysicsShapeDefinition when creating a shape. Friction typically ranges from 0.0 to 1.0, and bounciness from 0.0 (no bounce) to 1.0 (perfectly elastic).

Create a static body and set surfaceMaterial.tangentSpeed on its shape. The surface velocity drags resting objects along without moving the body itself, and you can update tangentSpeed at runtime by modifying the shape's surfaceMaterial struct.

Rolling resistance is a surface material property that simulates energy loss during rolling, preventing objects from rolling indefinitely. Higher values cause balls and wheels to stop sooner, useful for realistic ball behavior.

When two shapes collide, their material properties are combined by the physics engine. Friction typically uses multiplication or the minimum of both values, while restitution typically uses the maximum of both values.

Restitution values above 0.9 can cause instability, and values above 1.0 add energy to the system on each collision. Keep restitution between 0.0 and 0.3 for most objects to maintain stable behavior.