# MaskContainer

> Optimizes rendering of a VisualElement that has multiple descendants with nested masks.

## Definition

* **Type:** Field
* **Namespace:** [UnityEngine.UIElements](/engine/6000.6/script-reference/unityengine/uielements.md)
* **Assembly:** UnityEngine.UIElementsModule

```csharp
MaskContainer = 4
```

### Remarks

This option reduces stencil state changes and capitalizes on consecutive mask push/pop operations for efficiency.

Apply this option to a VisualElement with multiple nested masks among its descendants. For example, a child element has the `overflow: hidden;` style with rounded corners or SVG background.

The following illustration shows the number of batches in a single-level masking, a nested masking, and a nested masking with MaskContainer. The yellow color indicates the masking elements. The orange color indicates the masking element with MaskContainer applied. The numbers indicate the number of batches.

![MaskContainer (MaskContainer)](/api/media?file=/engine/6000.6/media/images/MaskContainer.png)

A: Single-level masking (1 batch)

B: Nested masking (5 batches)

C: Nested masking with MaskContainer (2 batches)

**Note**: Don't use GroupTransform in scenarios with many subtrees, where each subtree uses two or more levels of masking. This helps minimize consecutive push/push or pop/pop operations.