Sprite Particle System animation in viewController

Question

I create a macOS single window application and add a Sprite Particle System file with template Stars. and the visual effect just like this:

And I want to add it to my viewController, as the guide of this answer, I got the result like this, and it was not which I desired:

    override func viewDidLoad() {
        super.viewDidLoad()

        let scene = SCNScene()
        let particlesNode = SCNNode()
        let particleSystem = SCNParticleSystem(named: "Welcome", inDirectory: "")
        particlesNode.addParticleSystem(particleSystem!)
        scene.rootNode.addChildNode(particlesNode)
        skView.backgroundColor = .black
        skView.scene = scene
    }

So, I'm wondering what's wrong and what should I do?

Here is the demo repo: Link Here

The particle system itself is the standard "star" SceneKit particle system available in Xcode, with no changes.

Answer 1

Well I made a little progress. If I swivel the camera around 180 degrees, I can see the stars receding, so we can tell that the particle system is running ok. In the default orientation, though, all I saw was blinking lights. So I think the particles are being generated with a Z position of 0, the same as the camera's.

If I move the system's node away from the camera

    particlesNode.position = SCNVector3(0, 0, -20)

I still just see blinking lights. But if I click on the SCNView, the animation works correctly. I see stars coming at me.

I don't understand why I have to click the view to get it to work right. I tried isPlaying = true but that made no difference.