Version: 2021.3
Language : English
Collider surface bounciness
Create and apply a custom Physic Material

# How collider surface values combine

When two colliders are in contact, the physics system uses the surface properties of each to calculate the total friction and bounce between the two surfaces.

In Unity, you use the asset to control these parameters. The Physic Material asset is represented in the API by the `PhysicMaterial` class.

The Physic Material asset provides two properties: Friction Combine (`PhysicMaterial.frictionCombine`) and Bounce Combine (`PhysicMaterial.bounceCombine`). These properties each provide four options to control how the physics system calculates the total friction and bounce between two colliders:

Priority Property Description
1 Maximum Use the largest of the two values.
2 Multiply Use the sum of one value multiplied by the other.
3 Minimum Use the smallest of the two values.
4 Average Use the mean average of the two values; that is, the sum of both values, divided by two.

Friction Combine applies to both and Static Friction.

The properties in the table are in priority order. Unity takes priority into consideration when the colliders in a collider pair have Physic Material assets with different combine settings. For example, if one Physic Material asset’s Friction Combine is set to Average, and the other Physic Material asset’s Friction Combine is set to Maximum, Unity uses the Maximum calculation.

Collider surface bounciness
Create and apply a custom Physic Material