# PhysicsMaterial

> Talos next · Since 0.6; changed in next

What a collider is made of: its friction, its bounce and, for a character standing on it, how steep it may be before it is slid down.

Examples: an icy racetrack { friction: 0.02 }, a rubber bumper { restitution: 0.9 }, a slide { friction: 0.05, slopeLimit: 10 }.

## Fields

| Field | Type | Required | Default | Allowed values | Description |
|---|---|---|---|---|---|
| `friction` | `number` | no | `0` |  | Coulomb friction coefficient, 0 or more. Defaults to 0.5, or to the entity's rigidbody.friction when it has one; this wins over that when both are given. Rigid bodies use it as the solver does. A character controller standing on the collider takes its grip from it: friction / 0.5, capped at 1, scales how fast the character can speed up, slow down and turn. 0.05 is ice (a tenth of the grip), 0 keeps whatever velocity the character arrived with, and 0.5 or more is full grip. |
| `restitution` | `number` | no | `0` |  | Bounciness for rigid bodies, 0..1: 0 stops dead, 1 bounces back as fast as it arrived. Defaults to 0, or to the entity's rigidbody.restitution. The character controller does not bounce; a game that wants it adds velocity on the land event. |
| `slopeLimit` | `number` | no |  |  | Steepest slope, in degrees 0..90, that a character controller can stand on when the slope is this collider. It replaces the controller's own 45 degree limit on this collider only, in either direction: 10 turns a gentle icy ramp into something to slide down, 70 lets a grippy climbing wall be walked up. Absent keeps the controller's limit. |
| `surface` | `SurfaceKind` | no |  | `asphalt`, `concrete`, `cobble`, `wood`, `gravel`, `dirt`, `mud`, `grass`, `sand`, `snow`, `ice` | What a vehicle's tyres feel this ground as: its grip dry and soaked, its rolling resistance and how much water stands on it in the rain (docs/VEHICLES.md, Surfaces). Absent: as before (a road is asphalt; a terrain layer's grip comes from its friction). On a trigger collider it makes a zone: a wheel whose contact point is inside the volume feels this ground (an ice patch, a puddle, a gravel trap). |
| `tyreGrip` | `number` | no | `1` |  | A multiplier on the tyre grip of this ground, dry and wet, 0 or more. Default 1. An oil spill on asphalt is { surface: "asphalt", tyreGrip: 0.3 }. |
| `wetness` | `number` | no |  |  | How wet this ground is whatever the weather, 0 (dry) to 1 (soaked): a puddle, a hosed-down yard. Absent: the weather's wetness (`environment.weather`). |

## See also

- `SurfaceKind`