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# init(blendShapes:)

Creates a face geometry matching the facial expression described in the specified dictionary.

```
init?(blendShapes: [ARFaceAnchor.BlendShapeLocation : NSNumber])
```

## Parameters

`blendShapes`

A dictionary of blend shape coefficients describing a facial expression in terms of the positions of specific facial features. For any coefficient not specified in this dictionary, ARKit assumes a value of `0.0`.

## Return Value

A face geometry object, or `nil` if ARKit face tracking is not supported on the current device.

## Discussion

Each key in the `blendShapes` dictionary is an [`ARFaceAnchor.BlendShapeLocation`](/documentation/ARKit/ARFaceAnchor/BlendShapeLocation) constant identifying a facial feature. The corresponding value is the position of that feature relative to its neutral configuration, ranging from `0.0` (neutral) to `1.0` (maximum movement).

The format of this dictionary is identical to that provided by the [`ARFaceAnchor`](/documentation/ARKit/ARFaceAnchor) [`blendShapes`](/documentation/ARKit/ARFaceAnchor/blendShapes) property. You can use that property and this initializer to efficiently save and restore facial expression data; the serialized form of a blend shapes dictionary is more portable than that of the face mesh those coefficients describe.

---

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