ARkit Scene Kit Animations

Question

I'm building an app with ARkit and I'd like the user to have the ability to start and stop animations in the scene with the use of a button in the viewcontroller. However, I am having trouble finding an example of this code. Any pointers would be appreciated. For reference, my code is as follows for animating the dae file. I had a version working where I could stop the animation, but could not get it to restart. Thanks in advance.

func loadModels(atom: String) {

    // Create a new scene
        let scene = SCNScene(named: "art.scnassets/" + atom + ".scn")!

    // Set the scene to the view
    sceneViewAr?.scene = scene

    let mainnode = scene.rootNode.childNode(withName: "mainnode", recursively: true)
    mainnode?.runAction(SCNAction.rotateBy(x: 10, y: 0, z: 0, duration: 0))

    let orbit = scene.rootNode.childNode(withName: "orbit", recursively: true)
    orbit?.runAction(SCNAction.rotateBy(x: 0, y: 2 * 50, z: 0, duration: 100))

    if let orbittwo = scene.rootNode.childNode(withName: "orbit2", recursively: true) {
        orbittwo.runAction(SCNAction.rotateBy(x: 0, y: -2 * 50, z: 0, duration: 100))
    }

    if let orbitthree = scene.rootNode.childNode(withName: "orbit3", recursively: true) {
        orbitthree.runAction(SCNAction.rotateBy(x: 0, y: 2 * 50, z: 0, duration: 100))
    }

}

BlackMirrorz BlackMirrorz · Accepted Answer · 2018-07-21T08:20:41

I dont think there is a way to pause and stop in the way that you want per se.

Having said this you can make use of the following SCNAction functions:

 func action(forKey key: String) -> SCNAction?
 func removeAction(forKey key: String)

Essentially you are going to have to stop and then recreate the actions again.

As such you could do something like so:

Create a variable under your class declaration for your SCNActions so you dont have to rewrite them every time e.g:

let rotateXAction = SCNAction.rotateBy(x: 10, y: 0, z: 0, duration: 10)

Then Create 2 functions one to add and the other to remove the actions e.g:

/// Adds An SCNAction To A Specified Node With A Key
///
/// - Parameters:
///   - action: SCNAction
///   - node: SCNNode
///   - key: String
func addAction(_ action: SCNAction, toNode node: SCNNode, forKey key: String){

    node.runAction(action, forKey: key)
}


/// Removes An SCNAction For A Specified Node With A Key
///
/// - Parameters:
///   - action: SCNAction
///   - node: SCNNode,
///   - key: String
func removeActionFromNode(_ node: SCNNode, forKey key: String){

    node.removeAction(forKey: key)
}

Which you could then test like so:

/// Tests Whether The `SCNActions` Can Be Stated & Stopped
func testActions(){

    //1. Create An Array Of Colours
    let colours: [UIColor] = [.red, .green, .blue, .orange, .purple, .black]

    //2. Create An Array Of Face Materials
    var faceArray = [SCNMaterial]()

    //3. Create An SCNNode With An SCNBox Geometry
    let firstNode = SCNNode(geometry: SCNBox(width: 0.1, height: 0.1, length: 0.1, chamferRadius: 0))

    for faceIndex in 0..<colours.count{
        let material = SCNMaterial()
        material.diffuse.contents = colours[faceIndex]
        faceArray.append(material)
    }
    firstNode.geometry?.materials = faceArray

    //4. Add It To The Scene
    self.augmentedRealityView.scene.rootNode.addChildNode(firstNode)
    firstNode.position = SCNVector3(0 , 0, -1)

    //5. Run The Action
    addAction(rotateXAction, toNode: firstNode, forKey: "rotateX")


    //6. Stop It After 4 Seconds
    DispatchQueue.main.asyncAfter(deadline: .now() + 4) {
        self.removeActionFromNode(firstNode, forKey: "rotateX")

    }

    //7. Start It Again After 8
    DispatchQueue.main.asyncAfter(deadline: .now() + 8) {
        self.addAction(self.rotateXAction, toNode: firstNode, forKey: "rotateX")

    }
}

In your context you can easily tweak these functions to apply for a specific IBAction etc.

This is just a starter and in no way a refactored or refined example, however it should point you in the right direction...

ARkit Scene Kit Animations

1 Answers