# surfaceUp

> A reference direction used to calculate contact angles.

## Definition

* **Type:** Property
* **Namespace:** [UnityEngine](/engine/6000.7/script-reference/unityengine.md)
* **Assembly:** UnityEngine.Physics2DModule

```csharp
public Vector2 surfaceUp { readonly get; set; }
```

### Remarks

Both [\_surfaceSlideAngle](/engine/6000.7/script-reference/unityengine/rigidbody2d/slidemovement/surfaceslideangle.md) and [\_gravitySlipAngle](/engine/6000.7/script-reference/unityengine/rigidbody2d/slidemovement/gravityslipangle.md) use this to determine the surface angle.

The magnitude of this vector is typically unimportant as it is automatically normalized, however, if the magnitude is zero then both the [\_surfaceSlideAngle](/engine/6000.7/script-reference/unityengine/rigidbody2d/slidemovement/surfaceslideangle.md) and [\_gravitySlipAngle](/engine/6000.7/script-reference/unityengine/rigidbody2d/slidemovement/gravityslipangle.md) will be ignored resulting in always sliding and slipping. This can be used for moving in a "top down" view where gravity is not used and slipping is always required in all directions.

**NOTE:** By default, this value is [\_up](/engine/6000.7/script-reference/unityengine/vector2/up.md).

Additional Resources: [Rigidbody2D.Slide](/engine/6000.7/script-reference/unityengine/rigidbody2d/slide.md), [Rigidbody2D.SlideResults](/engine/6000.7/script-reference/unityengine/rigidbody2d/slideresults.md)