# indexStart

> The first index from an index buffer that defines a ray tracing geometry.

## Definition

* **Type:** Property
* **Namespace:** [UnityEngine.Rendering](/engine/6000.6/script-reference/unityengine/rendering.md)
* **Assembly:** UnityEngine.CoreModule

```csharp
public int indexStart { readonly get; set; }
```

### Remarks

This value must be a multiple of 3 and together with [RayTracingSubGeometryDesc.indexCount](/engine/6000.6/script-reference/unityengine/rendering/raytracingsubgeometrydesc/indexcount.md) it must define a valid range into an index buffer.