# animation The Core Animation object defining the behavior of the property animation. ``` var animation: CAAnimation { get set } ``` ## Discussion You can use different subclasses to animate effects in different ways. For example, a transitions a property from one value to another, and a transitions a property through a series of values. You use properties of the animation object to define its timing curve, repeat mode, and other options. SceneKit ignores the property of this animation object. Instead, when you attach a property controller to a particle system’s [`propertyControllers`](/documentation/SceneKit/SCNParticleSystem/propertyControllers) dictionary, use one of the keys listed in Particle Property Keys to specify which particle property it animates. SceneKit also ignores the animation’s and properties. Instead, the controller defines the behavior of the animation’s input value. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)