# Custom

> Transform tweens are not calculated or written. Instead, the callback target set with PhysicsWorld.transformWriteCallbackTarget which must implement PhysicsCallbacks.ITransformWriteCallback will be have PhysicsCallbacks.ITransformWriteCallback.OnTransformTweenWrite called allowing custom transform tween writing.

## Definition

* **Type:** Field
* **Namespace:** [Unity.U2D.Physics](/engine/7000.0/script-reference/unity/u2d/physics.md)
* **Assembly:** UnityEngine.PhysicsCore2DModule

```csharp
Custom = 3
```