參考:Best way to obtain ARKit or RealityKit camera rotation?

SceneKit很久沒有更新了, 鑒于蘋果推出的RealityKit, Reality Converter, Reality Composer, QuickLook, 全面轉(zhuǎn)向Reality家族是明智的. 雖然RealityKit提供了non-ar的選項(xiàng), 但一些最基礎(chǔ)的功能如鏡頭控制還是功能不全(類似于SceneKit中的.allowsCameraControl). 下面代碼是一個(gè)過度方案.

import UIKit
import RealityKit

class ViewController: UIViewController {
    @IBOutlet var arView: ARView!
    let buildings = try! Experience.loadScene()
    let camera = PerspectiveCamera()
    var current_X_Angle: Float = 0.0
    var current_Y_Angle: Float = 0.0

    override func viewDidLoad() {
        super.viewDidLoad()
        arView.environment.background = .color(.systemCyan)
        arView.scene.anchors.append(buildings)
        self.camera.position.z = 1
        buildings.children[0].addChild(self.camera)
        self.gestureRecognizer()
    }
    func gestureRecognizer() {
        for gestureRecognizer in [UIPanGestureRecognizer.self,
                                  UIPinchGestureRecognizer.self] {
            if gestureRecognizer == UIPinchGestureRecognizer.self {
                let r = UIPinchGestureRecognizer(target: self,
                               action: #selector(allowCameraControl_01))
                arView.addGestureRecognizer(r)
            }
            if gestureRecognizer == UIPanGestureRecognizer.self {
                let r = UIPanGestureRecognizer(target: self,
                               action: #selector(allowCameraControl_02))
                arView.addGestureRecognizer(r)
            }
        }
    }
    @objc func allowCameraControl_01(recognizer: UIPinchGestureRecognizer) {
        switch recognizer.state {
            case .changed, .ended:
                self.camera.position.z *= 1 / Float(recognizer.scale)
                recognizer.scale = 1.0
            default: break
        }
    }
    @objc func allowCameraControl_02(recognizer: UIPanGestureRecognizer) {
        switch recognizer.state {
            case .changed, .ended:
                let translate = recognizer.translation(in: recognizer.view)
                let angle_X = Float(translate.y / 300) * .pi / 180.0
                let angle_Y = Float(translate.x / 100) * .pi / 180.0
                self.current_X_Angle += angle_X
                self.current_Y_Angle += angle_Y                
                camera.setOrientation(Transform(pitch: current_X_Angle,
                                                  yaw: current_Y_Angle,
                                                 roll: .zero).rotation,
                                      relativeTo: buildings.anchor)
            default: break
        }
    }
}