---
title: geometryDescriptors
framework: metal
role: symbol
role_heading: Instance Property
path: metal/mtlprimitiveaccelerationstructuredescriptor/geometrydescriptors
---

# geometryDescriptors

An array that contains the individual pieces of geometry that compose the acceleration structure.

## Declaration

```swift
var geometryDescriptors: [MTLAccelerationStructureGeometryDescriptor]? { get set }
```

## Discussion

Discussion The value of the motionKeyframeCount property determines what kinds of geometry descriptors you can assign to this property and how you need to configure them. If the value of motionKeyframeCount is greater than 1, then the geometry descriptors need to be either MTLAccelerationStructureMotionBoundingBoxGeometryDescriptor or MTLAccelerationStructureMotionTriangleGeometryDescriptor objects. Further, you need to provide exactly that many keyframes of data when creating those geometry descriptors. If motionKeyframeCount  is 1, use MTLAccelerationStructureBoundingBoxGeometryDescriptor or MTLAccelerationStructureTriangleGeometryDescriptor objects instead.

## See Also

### Related Documentation

- [motionKeyframeCount](metal/mtlprimitiveaccelerationstructuredescriptor/motionkeyframecount.md)