---
title: "init(by:timing:isAdditive:)"
framework: realitykit
role: symbol
role_heading: Initializer
path: "realitykit/fromtobyaction/init(by:timing:isadditive:)"
---

# init(by:timing:isAdditive:)

Creates a new action to animate from the deaultSource by a transform relative to the starting transform.

## Declaration

```swift
init(by: Value, timing: AnimationTimingFunction = .linear, isAdditive: Bool = false)
```

## Parameters

- `by`: Transform which is used to increment the starting transform. Used to determine the final transform we animate towards.
- `timing`: Controls the progress of the animation.
- `isAdditive`: Specifies whether you can additively blend the output from the action’s animation.

## Discussion

Discussion defaultSource → defaultSource + by