---
title: mask
framework: metal
role: symbol
role_heading: Instance Property
path: metal/mtlaccelerationstructureinstancedescriptor/mask
---

# mask

A mask to use for the instance when testing a ray against the geometry.

## Declaration

```swift
var mask: UInt32
```

## Discussion

Discussion Metal reserves the top 24 bits for future use.

## See Also

### Customizing intersection and hit tests for the instance

- [intersectionFunctionTableOffset](metal/mtlaccelerationstructureinstancedescriptor/intersectionfunctiontableoffset.md)
- [options](metal/mtlaccelerationstructureinstancedescriptor/options.md)