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# MTLTessellationFactorStepFunction

Options for specifying the step function that determines the tessellation factors for a patch from the tessellation factor buffer.

```
enum MTLTessellationFactorStepFunction
```

## Topics

### Factor step functions

[`MTLTessellationFactorStepFunction.constant`](/documentation/Metal/MTLTessellationFactorStepFunction/constant)

A constant step function. For all instances, the tessellation factor for all patches in a patch draw call is at the `offset` location in the tessellation factor buffer.

[`MTLTessellationFactorStepFunction.perPatch`](/documentation/Metal/MTLTessellationFactorStepFunction/perPatch)

A per-patch step function. For all instances, the tessellation factor for all patches in a patch draw call is at the `offset + (drawPatchIndex * tessellationFactorStride)` location in the tessellation factor buffer.

[`MTLTessellationFactorStepFunction.perInstance`](/documentation/Metal/MTLTessellationFactorStepFunction/perInstance)

A per-instance step function. For a given instance ID, the tessellation factor for a patch in a patch draw call is at the `offset + (instanceID * instanceStride)` location in the tessellation factor buffer.

[`MTLTessellationFactorStepFunction.perPatchAndPerInstance`](/documentation/Metal/MTLTessellationFactorStepFunction/perPatchAndPerInstance)

A per-patch and per-instance step function. For a given instance ID, the tessellation factor for a patch in a patch draw call is at the `offset + (drawPatchIndex * tessellationFactorStride + instanceID * instanceStride)` location in the tessellation factor buffer.


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