ARFace.swift

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 判斷是否裝置支援 ar face 功能
        guard ARFaceTrackingConfiguration.isSupported else { fatalError() }
        sceneView.delegate = self
    }
    
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        
        // 畫面顯示的時候，才會開啟功能
        let configuration = ARFaceTrackingConfiguration()
        sceneView.session.run(configuration)
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        
        // 離開時則關閉
        sceneView.session.pause()
    }