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# MTLVertexStepFunction

The frequency with which the vertex function or post-tessellation vertex function fetches attribute data.

```
enum MTLVertexStepFunction
```

## Topics

### Step functions

[`MTLVertexStepFunctionConstant`](/documentation/Metal/MTLVertexStepFunction/constant)

The vertex function fetches attribute data once and uses that data for every vertex.

[`MTLVertexStepFunctionPerVertex`](/documentation/Metal/MTLVertexStepFunction/perVertex)

The vertex function fetches and uses new attribute data for every vertex.

[`MTLVertexStepFunctionPerInstance`](/documentation/Metal/MTLVertexStepFunction/perInstance)

The vertex function regularly fetches new attribute data for a number of instances that is determined by `stepRate`.

[`MTLVertexStepFunctionPerPatch`](/documentation/Metal/MTLVertexStepFunction/perPatch)

The post-tessellation vertex function fetches data based on the patch index of the patch.

[`MTLVertexStepFunctionPerPatchControlPoint`](/documentation/Metal/MTLVertexStepFunction/perPatchControlPoint)

The post-tessellation vertex function fetches data based on the control-point indices associated with the patch.

## Relationships

### Conforms To

[`SendableMetatype`](/documentation/Swift/SendableMetatype)

[`Equatable`](/documentation/Swift/Equatable)

[`Hashable`](/documentation/Swift/Hashable)

[`Sendable`](/documentation/Swift/Sendable)

[`RawRepresentable`](/documentation/Swift/RawRepresentable)

[`BitwiseCopyable`](/documentation/Swift/BitwiseCopyable)

---

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