# vertexStart

> The index of the first vertex from RayTracingGeometryInstanceConfig.vertexBuffer that defines this ray tracing geometry instance.

## Definition

* **Type:** Property
* **Namespace:** [UnityEngine.Rendering](/engine/6000.5/script-reference/unityengine/rendering.md)
* **Assembly:** UnityEngine.CoreModule

```csharp
public uint vertexStart { readonly get; set; }
```