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# particleVelocityVariation

The range, in units per second, of randomized initial particle speeds. Animatable.

```
var particleVelocityVariation: CGFloat { get set }
```

## Discussion

Setting a nonzero value for this property randomizes the effect of the [`particleVelocity`](/documentation/SceneKit/SCNParticleSystem/particleVelocity) property. SceneKit randomly adjusts the initial speed of each particle by up to half the [`particleVelocityVariation`](/documentation/SceneKit/SCNParticleSystem/particleVelocityVariation) value. For example, if the [`particleVelocity`](/documentation/SceneKit/SCNParticleSystem/particleVelocity) value is `10.0` units per second and the [`particleVelocityVariation`](/documentation/SceneKit/SCNParticleSystem/particleVelocityVariation) value is `5.0` units per second, newly spawned particles have random velocities between `7.5` and `12.5` units per second.

The default value is `0.0` units per second, specifying no randomization.

You can animate changes to this property’s value. See [Animating SceneKit Content](/documentation/SceneKit/animating-scenekit-content).

---

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