# Sandbox.ModelBuilder.AddCollisionSphere

```csharp
ModelBuilder AddCollisionSphere(float radius, Vector3 center = null)
```

Adds a sphere collision shape.

### Parameters

- `radius` (`float`): The sphere radius.
- `center` (`Vector3`), default `null`: The sphere center.

### Returns

`ModelBuilder`

Declared in [Sandbox.ModelBuilder](/api/Sandbox.ModelBuilder).
Assembly: `Sandbox.Engine`.