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# boneWeights

The geometry source that defines the influence of each bone on the positions the geometry’s vertices.

```
var boneWeights: SCNGeometrySource { get }
```

## Discussion

This geometry source’s [`semantic`](/documentation/SceneKit/SCNGeometrySource/semantic-swift.property) property must be [`boneWeights`](/documentation/SceneKit/SCNGeometrySource/Semantic-swift.struct/boneWeights). Its data is an array of floating-point vectors, whose [`componentsPerVector`](/documentation/SceneKit/SCNGeometrySource/componentsPerVector) count is the number of bones influencing each vertex. Each vector corresponds to a vertex in the geometry’s [`vertex`](/documentation/SceneKit/SCNGeometrySource/Semantic-swift.struct/vertex) geometry source, and each component in a vector specifies the influence of a bone on that vertex’s position. The [`boneIndices`](/documentation/SceneKit/SCNSkinner/boneIndices) source determines which nodes in the bones array correspond to each component in the vector. A component value of `0.0` means that the bone has no influence on that vertex; positive or negative values scale the transformation of a bone node before SceneKit applies that transformation to the vertex.

> Note:
> SceneKit performs skeletal animation on the GPU only if the ``doc://com.apple.scenekit/documentation/SceneKit/SCNGeometrySource/componentsPerVector`` count in this geometry source is `4` or less. Larger vectors result in CPU-based animation and drastically reduced rendering performance.

---

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