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# motionStartTime

A starting time for the range of motion that the key-frame data represents.

```
var motionStartTime: Float
```

## Discussion

The [`motionTransformsStartIndex`](/documentation/Metal/MTLAccelerationStructureMotionInstanceDescriptor/motionTransformsStartIndex) and [`motionTransformsCount`](/documentation/Metal/MTLAccelerationStructureMotionInstanceDescriptor/motionTransformsCount) properties
represent the key-frame motion data.

The property’s default value is `0.0`.

---

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