---
title: MTLAccelerationStructureInstanceDescriptorType.userID
framework: metal
role: symbol
role_heading: Case
path: metal/mtlaccelerationstructureinstancedescriptortype/userid
---

# MTLAccelerationStructureInstanceDescriptorType.userID

An option specifying that the instance contains a user identifier.

## Declaration

```swift
case userID
```

## Discussion

Discussion This instance type corresponds to the MTLAccelerationStructureUserIDInstanceDescriptor structure memory layout.

## See Also

### Specifying the instance descriptor type

- [MTLAccelerationStructureInstanceDescriptorType.default](metal/mtlaccelerationstructureinstancedescriptortype/default.md)
- [MTLAccelerationStructureInstanceDescriptorType.motion](metal/mtlaccelerationstructureinstancedescriptortype/motion.md)
- [MTLAccelerationStructureInstanceDescriptorType.indirect](metal/mtlaccelerationstructureinstancedescriptortype/indirect.md)
- [MTLAccelerationStructureInstanceDescriptorType.indirectMotion](metal/mtlaccelerationstructureinstancedescriptortype/indirectmotion.md)