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# setAccelerationStructure(_:index:)

Encodes a reference to an acceleration structure into the argument buffer.

```
func setAccelerationStructure(_ accelerationStructure: (any MTLAccelerationStructure)?, index: Int)
```

## Parameters

`accelerationStructure`

An acceleration structure the method encodes.

`index`

The index of an acceleration structure within the argument buffer.
The value corresponds to either the index ID of a declaration in
Metal Shading Language (MSL) or the [`index`](/documentation/Metal/MTLArgumentDescriptor/index) property of
an [`MTLArgumentDescriptor`](/documentation/Metal/MTLArgumentDescriptor) instance.

## Discussion

---

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