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# MTLAccelerationStructureSizes

The expected sizes for a ray-tracing acceleration structure.

```
struct MTLAccelerationStructureSizes
```

## Topics

### Retrieving the sizes

[`accelerationStructureSize`](/documentation/Metal/MTLAccelerationStructureSizes/accelerationStructureSize)

The size of the acceleration structure, in bytes.

[`buildScratchBufferSize`](/documentation/Metal/MTLAccelerationStructureSizes/buildScratchBufferSize)

The amount of scratch memory, in bytes, the GPU devices needs to build the acceleration structure.

[`refitScratchBufferSize`](/documentation/Metal/MTLAccelerationStructureSizes/refitScratchBufferSize)

The amount of scratch memory, in bytes, the GPU device needs to refit the acceleration structure.

### Creating an acceleration size structure

[`init()`](/documentation/Metal/MTLAccelerationStructureSizes/init())

Creates an acceleration sizes instance with default values.

[`init(accelerationStructureSize:buildScratchBufferSize:refitScratchBufferSize:)`](/documentation/Metal/MTLAccelerationStructureSizes/init(accelerationStructureSize:buildScratchBufferSize:refitScratchBufferSize:))

Creates an acceleration sizes instance with specific values.


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