问如何从世界上测量虚拟物体的位移角？

EN

import RealityKit
import Combine

class ViewController: UIViewController {    
    @IBOutlet var arView: ARView!
    @IBOutlet var label: UILabel!
    var model = ModelEntity()
    var subs: [AnyCancellable] = []

    override func viewDidLoad() {
        super.viewDidLoad()    
        self.model = ModelEntity(mesh: .generateSphere(radius: 0.1))
        self.model.position.z = -10
        let transA = Transform(translation: [ 3, 0,-10])
        let transB = Transform(translation: [ 1, 0,-4 ])
        let transC = Transform(translation: [-1, 0,-2 ])
        
        DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
            self.model.move(to: transA, relativeTo: nil, duration: 1)
            DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
                self.model.move(to: transB, relativeTo: nil, duration: 1)
                DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
                    self.model.move(to: transC, relativeTo: nil, duration: 1)
                }
            }
        }            
        let anchor = AnchorEntity(world: [0, 0, 0])
        anchor.addChild(self.model)
        arView.scene.anchors.append(anchor)
                
        arView.scene.subscribe(to: SceneEvents.Update.self) { _ in    
            let orb: Float = atan2(self.model.position.x, 
                                   self.model.position.z)   
            self.label.text = "Angle: \(String(format: "%.1f" 
                                              (orb * 180 / -.pi)))"
        }.store(in: &subs)
    }
}