SceneKit SCNSceneRendererDelegate - renderer function not called

Question

I recently asked a question which had a pretty obvious answer. I'm still working on the same project and running into another problem. I need to implement per frame logic and the SCNSceneRendererDelegate protocol worked perfectly fine on iOS, but on OSX, the renderer function is not firing. I have created a little example project to illustrate my problem. It consists of a Scene Kit View in storyboard and following code in the ViewController class:

import Cocoa
import SceneKit

class ViewController: NSViewController, SCNSceneRendererDelegate {

    @IBOutlet weak var sceneView: SCNView!

    let cubeNode = SCNNode()

    override func viewDidLoad() {

        super.viewDidLoad()

        let scene = SCNScene()

        let sphere = SCNSphere(radius: 0.1)
        sphere.firstMaterial!.diffuse.contents = NSColor.yellowColor()
        let sphereNode = SCNNode(geometry: sphere)
        scene.rootNode.addChildNode(sphereNode)

        let cube = SCNBox(width: 0.2, height: 0.2, length: 0.2, chamferRadius: 0)
        cube.firstMaterial!.diffuse.contents = NSColor.greenColor()
        cubeNode.geometry = cube
        cubeNode.position = SCNVector3(1,0,0)
        scene.rootNode.addChildNode(cubeNode)

        let cameraNode = SCNNode()
        cameraNode.camera = SCNCamera()
        cameraNode.position = SCNVector3(2, 1, 2)
        let constraint = SCNLookAtConstraint(target: cubeNode)
        cameraNode.constraints = [constraint]
        scene.rootNode.addChildNode(cameraNode)

        sceneView.scene = scene
        sceneView.backgroundColor = NSColor(red: 0.5, green: 0, blue: 0.3, alpha: 1)
        sceneView.allowsCameraControl = true

        sceneView.delegate = self
        sceneView.playing = true

    }

    func renderer(renderer: SCNSceneRenderer, updateAtTime time: NSTimeInterval) {
        cubeNode.position.x += 0.1
    }
}

All I want is to basically move the cube with every frame. But nothing happens. What is weird is that when I set sceneView.allowsCameraControl to true, the renderer function is called whenever I click or drag on the screen (which makes sense because it needs to update the view based on camera angles). But I would want it to be called every frame.

Is there an error I don't see or is this a bug in my Xcode?

Edit: I have tried following the instructions in the answer below and now have the following code for the ViewController:

import Cocoa
import SceneKit

class ViewController: NSViewController {

    @IBOutlet weak var sceneView: SCNView!
    let scene = MyScene(create: true)

    override func viewDidLoad() {

        super.viewDidLoad()

        sceneView.scene = scene
        sceneView.backgroundColor = NSColor(red: 0.5, green: 0, blue: 0.3, alpha: 1)
        sceneView.allowsCameraControl = true

        sceneView.delegate = scene
        sceneView.playing = true

    }

}

And a MyScene class:

import Foundation
import SceneKit

final class MyScene: SCNScene, SCNSceneRendererDelegate {

    let cubeNode = SCNNode()

    convenience init(create: Bool) {
        self.init()

        let sphere = SCNSphere(radius: 0.1)
        sphere.firstMaterial!.diffuse.contents = NSColor.yellowColor()
        let sphereNode = SCNNode(geometry: sphere)
        rootNode.addChildNode(sphereNode)

        let cube = SCNBox(width: 0.2, height: 0.2, length: 0.2, chamferRadius: 0)
        cube.firstMaterial!.diffuse.contents = NSColor.greenColor()
        cubeNode.geometry = cube
        cubeNode.position = SCNVector3(1,0,0)
        rootNode.addChildNode(cubeNode)

        let cameraNode = SCNNode()
        cameraNode.camera = SCNCamera()
        cameraNode.position = SCNVector3(2, 1, 2)
        let constraint = SCNLookAtConstraint(target: cubeNode)
        cameraNode.constraints = [constraint]

        rootNode.addChildNode(cameraNode)
    }

    @objc func renderer(aRenderer: SCNSceneRenderer, updateAtTime time: NSTimeInterval) {
        cubeNode.position.x += 0.01
    }
}

However, it is still not working. What am I doing wrong?

Edit: setting sceneView.loops = true fixes the described problem

Answer 1

I suspect the answer hinges on what Querent means by "every frame". Querent should probably clarify this, but I'll try to answer anyway because I'm like that.

The simplest interpretation is probably "every frame that would render anyway", but that seems unlikely to be what is desired unless the cube is intended as a kind of activity monitor for the renderer, which doesn't seem likely either; there are much better approaches to that.

What Querent may want is to render repeatedly while the view's playing property is YES. If that's the case, then perhaps the answer is as simple as setting the view's loops property to YES. This recently solved a problem for me in which I wanted rendering to occur while a keyboard key was held down. (I had noticed that setting playing to YES would induce a single call to my delegate.)