I'm currently converting my game from SceneKit to RealityKit. What's the easiest way to run an animation in which every frame I want to run custom code, similar to SCNAction.customAction which accepts a callback that is called repeatedly until the action completes?

I'm trying to convert my game from SceneKit to RealityKit. I noticed that even when the scene is static (nothing moves), RealityKit keeps using CPU. In SceneKit, CPU goes down to 0% with a static scene. With this simplest of games, RealityKit keeps using about 65% CPU: class ViewController: NSViewController { override func loadView() { view = ARView(frame: NSScreen.main!.frame) } } Is this expected or a bug? I created FB22125047.

I'm converting my game from SceneKit to RealityKit. It has a SpriteKit overlay that according to Explore advanced rendering with RealityKit 2 I can add with the code below. The code runs fine if the SKScene only contains a SKSpriteNode (see the commented out line), but when I add a SKShapeNode with a fillColor instead, the app crashes with this error: -[MTLDebugRenderCommandEncoder validateCommonDrawErrors:]:5970: failed assertion `Draw Errors Validation MTLDepthStencilDescriptor uses frontFaceStencil but MTLRenderPassDescriptor has a nil stencilAttachment texture MTLDepthStencilDescriptor uses backFaceStencil but MTLRenderPassDescriptor has a nil stencilAttachment texture ' I don't know enough about low-level graphics and stencils yet to figure out a quick solution, so I would appreciate if anyone could share an easy fix or explanation of what's wrong. Thanks! class ViewController: NSViewController { var device: MTLDevice! var renderer: SKRenderer! override func loadView() { let arView = ARView(frame: NSScreen.main!.frame) view = arView arView.renderCallbacks.prepareWithDevice = { [weak self] device in guard let self = self else { return } self.device = device renderer = SKRenderer(device: MTLCreateSystemDefaultDevice()!) let scene = SKScene() let shape = SKShapeNode(rectOf: CGSize(width: 10, height: 10)) shape.fillColor = .red scene.addChild(shape) // scene.addChild(SKSpriteNode(color: .red, size: CGSize(width: 10, height: 10))) renderer.scene = scene } arView.renderCallbacks.postProcess = { [weak self] context in guard let self = self else { return } let encoder = context.commandBuffer.makeBlitCommandEncoder() encoder?.copy(from: context.sourceColorTexture, to: context.targetColorTexture) encoder?.endEncoding() renderer.update(atTime: context.time) let descriptor = MTLRenderPassDescriptor() descriptor.colorAttachments[0].loadAction = .load descriptor.colorAttachments[0].storeAction = .store descriptor.colorAttachments[0].texture = context.targetColorTexture renderer.render(withViewport: CGRect(x: 0, y: 0, width: context.targetColorTexture.width, height: context.targetColorTexture.height), commandBuffer: context.commandBuffer, renderPassDescriptor: descriptor) } } }