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# init(screenSize:label:)

A convenience initializer that creates a rate map descriptor with a given size and identifier.

```
convenience init(screenSize: MTLSize, label: String? = nil)
```

## Parameters

`screenSize`

The logical size, in pixels, of the viewport coordinate system.

`label`

A string that identifies the resulting rate map.

## Return Value

A descriptor object whose [`screenSize`](/documentation/Metal/MTLRasterizationRateMapDescriptor/screenSize) and [`label`](/documentation/Metal/MTLRasterizationRateMapDescriptor/label) properties are set to the provided values. You need to add at least one layer rate map to the descriptor.

---

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