# isTopLevel

> With this option enabled, Unity builds a top level BVH (for instances). When disabled, it builds a bottom level BVH (for a Mesh).

## Definition

* **Type:** Property
* **Namespace:** [UnityEditor.Embree](/engine/6000.6/script-reference/unityeditor/embree.md)
* **Assembly:** UnityEditor

```csharp
public bool isTopLevel { readonly get; set; }
```