---
title: MTLStepFunction.threadPositionInGridX
framework: metal
role: symbol
role_heading: Case
path: metal/mtlstepfunction/threadpositioningridx
---

# MTLStepFunction.threadPositionInGridX

The compute function fetches data based on the thread’s x coordinate.

## Declaration

```swift
case threadPositionInGridX
```

## Discussion

Discussion This step function uses the x coordinate of the thread position in a grid as the index to fetch [[stage_in]] data. In tessellation compute kernels, you use this step function to identify a control point in a given patch.

## See Also

### Step options

- [MTLStepFunction.constant](metal/mtlstepfunction/constant.md)
- [MTLStepFunction.perInstance](metal/mtlstepfunction/perinstance.md)
- [MTLStepFunction.perPatch](metal/mtlstepfunction/perpatch.md)
- [MTLStepFunction.perPatchControlPoint](metal/mtlstepfunction/perpatchcontrolpoint.md)
- [MTLStepFunction.perVertex](metal/mtlstepfunction/pervertex.md)
- [MTLStepFunction.threadPositionInGridY](metal/mtlstepfunction/threadpositioningridy.md)
- [MTLStepFunction.threadPositionInGridXIndexed](metal/mtlstepfunction/threadpositioningridxindexed.md)
- [MTLStepFunction.threadPositionInGridYIndexed](metal/mtlstepfunction/threadpositioningridyindexed.md)