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# SCNActionTimingFunction

The signature for a block that manages animation timing, used by the [`timingFunction`](/documentation/SceneKit/SCNAction/timingFunction) property.

```
typealias SCNActionTimingFunction = (Float) -> Float
```

## Discussion

The block takes a single parameter:

- time: A fraction of the action’s The input value for the timing function, as determined by the [`timingMode`](/documentation/SceneKit/SCNAction/timingMode) property and the action’s current progress.

Your block must return a floating-point value between `0.0` and `1.0`, where `0.0` represents the starting state of the action’s animation and `1.0` represents the end state.

---

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