# ARView.RenderCallbacks A container that holds the view’s render callbacks. ``` struct RenderCallbacks ``` ## Overview Render callbacks are closures RealityKit calls at predefined times. You can use render callbacks to modify the results of RealityKit’s rendering. If you assign a function or closure to any of the contained callback properties, RealityKit calls that function or closure at a predefined time. Setting the [`postProcess`](/documentation/RealityKit/ARView/RenderCallbacks-swift.struct/postProcess) property, for example, causes RealityKit to call the assigned function or closure every frame, after RealityKit renders the scene, but before it displays it. ## Topics ### Creating a callback object [`init()`](/documentation/RealityKit/ARView/RenderCallbacks-swift.struct/init()) Creates a new object. ### Register callback closures [`var prepareWithDevice: ((any MTLDevice) -> Void)?`](/documentation/RealityKit/ARView/RenderCallbacks-swift.struct/prepareWithDevice) A callback function for doing initial setup work. [`var postProcess: ((ARView.PostProcessContext) -> Void)?`](/documentation/RealityKit/ARView/RenderCallbacks-swift.struct/postProcess) A callback function for implementing postprocess effects. --- 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)