# ComputeMaterialsCRC

> Causes RayTracingAccelerationStructure.CullInstances to compute the CRC hash values of all unique Materials used by ray tracing instances that were added to the acceleration structure.

## Definition

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

```csharp
ComputeMaterialsCRC = 8
```

### Remarks

The array of Material CRC values is returned by [RayTracingAccelerationStructure.CullInstances](/engine/6000.5/script-reference/unityengine/rendering/raytracingaccelerationstructure/cullinstances.md) in [RayTracingInstanceCullingResults](/engine/6000.5/script-reference/unityengine/rendering/raytracinginstancecullingresults.md).

The cost for enabling this flag depends on how complex the Materials are and how many different Materials are used in a Scene. The CRC array can be used for example to reset the convergence during path tracing if a Material property has changed between frames.

Additional Resources: [Material.ComputeCRC()](/engine/6000.5/script-reference/unityengine/material/computecrc.md), [HashUtilities](/engine/6000.5/script-reference/unityengine/hashutilities.md).