如何使用SceneKit实现3D指南针

import UIKit
import SceneKit
import CoreMotion

class ViewController: UIViewController {
    var sceneView: SCNView!
    var scene: SCNScene!
    var compassNode: SCNNode!
    var motionManager: CMMotionManager!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建SCNView
        sceneView = SCNView(frame: view.bounds)
        view.addSubview(sceneView)
        
        // 创建SCNScene
        scene = SCNScene()
        sceneView.scene = scene
        
        // 创建指南针模型
        let compassGeometry = SCNBox(width: 1, height: 0.1, length: 1, chamferRadius: 0)
        let compassMaterial = SCNMaterial()
        compassMaterial.diffuse.contents = UIColor.red
        compassGeometry.materials = [compassMaterial]
        compassNode = SCNNode(geometry: compassGeometry)
        
        // 设置指南针节点的位置和旋转
        compassNode.position = SCNVector3(0, 0, -5)
        compassNode.eulerAngles = SCNVector3(0, 0, 0)
        
        // 添加节点到场景
        scene.rootNode.addChildNode(compassNode)
        
        // 设置场景和相机
        scene.background.contents = UIColor.white
        let cameraNode = SCNNode()
        cameraNode.camera = SCNCamera()
        scene.rootNode.addChildNode(cameraNode)
        cameraNode.position = SCNVector3(0, 0, 10)
        
        // 初始化CMMotionManager
        motionManager = CMMotionManager()
        motionManager.startDeviceMotionUpdates()
        
        // 开始更新指南针旋转
        startUpdatingCompass()
    }
    
    func startUpdatingCompass() {
        // 使用设备的方向数据更新指南针旋转
        motionManager.startDeviceMotionUpdates(to: OperationQueue.main) { (motion, error) in
            guard let motion = motion else { return }
            
            // 获取设备的方向数据
            let attitude = motion.attitude
            let roll = attitude.roll
            let pitch = attitude.pitch
            let yaw = attitude.yaw
            
            // 更新指南针节点的旋转
            self.compassNode.eulerAngles = SCNVector3(pitch, -yaw, roll)
        }
    }
}