UNITY • 3D PHYSX ASSETS
UNITY PHYSIC MATERIALS: FRICTION & BOUNCINESS
Learn how to customize surface friction, simulate rubber bouncing, configure ice sliding, and master friction combine formulas in Unity.
1. Core Physic Material Properties
A Physic Material (or Physics Material in Unity 6) is an asset assigned to Colliders to determine how their surfaces interact when contacting other colliders:
Dynamic Friction (0.0 to 1.0+)
Friction applied when an object is already moving / sliding against a surface. (e.g.
0.05 for ice, 0.8 for rubber).
Static Friction (0.0 to 1.0+)
Friction required to start moving an object at rest on an inclined slope. Must be equal to or higher than dynamic friction.
Bounciness (0.0 to 1.0)
Restitution coefficient.
0.0 means no bounce (all energy absorbed); 1.0 means a 100% elastic bounce without loss.
2. Understanding Combine Modes
When two colliders touch, PhysX uses the Combine Mode to decide the final friction and bounciness calculation:
- Average:
(MaterialA + MaterialB) / 2(Standard default). - Minimum:
Min(MaterialA, MaterialB)→ Essential for Ice: Guarantees that if one surface has 0 friction, the contact is always slick regardless of what touches it! - Maximum:
Max(MaterialA, MaterialB)→ Takes the highest friction or bounce. - Multiply:
MaterialA * MaterialB→ Multiplies the two coefficients.
3. Production Material Presets Table
Slick Ice Track
Dynamic Friction:
Static Friction:
Bounciness:
Friction Combine: Minimum
0.02Static Friction:
0.02Bounciness:
0.1Friction Combine: Minimum
Grippy Asphalt Road
Dynamic Friction:
Static Friction:
Bounciness:
Friction Combine: Average
0.75Static Friction:
0.90Bounciness:
0.0Friction Combine: Average
Super Rubber Ball
Dynamic Friction:
Static Friction:
Bounciness:
Bounce Combine: Maximum
0.4Static Friction:
0.4Bounciness:
0.92Bounce Combine: Maximum
Related Physics Guides & Tools
Frequently Asked Questions
Unity clamps the Bounciness slider between
0.0 and 1.0. Setting it above 1.0 would create a perpetual motion machine that generates infinite kinetic energy with every bounce, eventually triggering physics solver NaN exceptions.
Select your Unity Terrain GameObject in the hierarchy, find the
TerrainCollider component in the Inspector, and drag your Physic Material asset into the Material slot.