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# interpolateBetween(_:withWeight:)

Returns a new parameter value which has been calculated by interpolating between                 two key values.

```
func interpolateBetween(_ rightValue: any NSCopying & NSSecureCoding & NSObjectProtocol, withWeight weight: Float) -> any NSCopying & NSSecureCoding & NSObjectProtocol
```

## Parameters

`rightValue`

The value of the custom parameter at the keypoint to the right of the current time in the timeline.

`weight`

A floating-point value between `0` and `1` representing the weight of the keyframe to the right of the current time vs the keyframe to the left of the current time. A weight of `0` means the same value as the keyframe to the left; a weight of `1` means the same value as the keyframe to the right.

## Return Value

A new custom parameter value.

## Discussion

This plug-in method is called by the host application when the user has added keyframes to a custom parameter, and the application needs to know the value of the parameter between keyframes. This may be when the application is rendering a frame between keyframes, or when the plugin requests the value of its parameter at a time between keyframes, or when the application displays UI.

---

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