Ios 在相机动作之前快速防止场景视点重置

我有一个用SceneKit构建的3D互动地球仪，其中国家用圆点表示.下面的函数获取一个位置，并将相机动画设置为该位置.

如果用户没有与地球交互，那么我能够连续调用该函数并将相机动画设置到新位置.

但是，如果用户在场景中执行任何手势，则相机动画不起作用.

A solution found in a different SO thread (linked below) used the line sceneView.pointOfView = cameraNode at the beginning of the function.
This did solve the issue of the camera not animating after a gesture.

但是，这条线会使球体在设置动画之前重置到其原始位置.我一直在想办法绕过这个场景重置，但一直没有成功.

我假设在地球上做一个手势会为场景创建一个新的视点，并覆盖相机的视点.因此，在动画之前将场景的视点设置回摄影机可以解决该问题.

import Foundation
import SceneKit
import CoreImage
import SwiftUI
import MapKit

public typealias GenericController = UIViewController

public class GlobeViewController: GenericController {
    var nodePos: CGPoint? = nil
    public var earthNode: SCNNode!
    private var sceneView : SCNView!
    private var cameraNode: SCNNode!
    private var dotCount = 50000
    
    public init(earthRadius: Double) {
        self.earthRadius = earthRadius
        super.init(nibName: nil, bundle: nil)
    }
    
    public init(earthRadius: Double, dotCount: Int) {
        self.earthRadius = earthRadius
        self.dotCount = dotCount
        super.init(nibName: nil, bundle: nil)
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    func centerCameraOnDot(dotPosition: SCNVector3) {
        sceneView.pointOfView = cameraNode //HERE RESETS
        
        let fixedDistance: Float = 5.0
        let newCameraPosition = dotPosition.normalized().scaled(to: fixedDistance)

        let moveAction = SCNAction.move(to: newCameraPosition, duration: 1.5)

        let constraint = SCNLookAtConstraint(target: earthNode)
        constraint.isGimbalLockEnabled = true

        sceneView.gestureRecognizers?.forEach { $0.isEnabled = false }
        
        SCNTransaction.begin()
        SCNTransaction.animationDuration = 1.5

        self.cameraNode.constraints = [constraint]
        self.cameraNode.runAction(moveAction) {
            DispatchQueue.main.async {
                self.sceneView.gestureRecognizers?.forEach { $0.isEnabled = true }
            }
        }
        SCNTransaction.commit()
    }

    public override func viewDidLoad() {
        super.viewDidLoad()
        setupScene()
        
        setupParticles()
        
        setupCamera()
        setupGlobe()
        
        setupDotGeometry()
    }
    
    private func setupScene() {
        let scene = SCNScene()
        sceneView = SCNView(frame: view.frame)
        sceneView.scene = scene
        sceneView.showsStatistics = true
        sceneView.backgroundColor = .clear
        sceneView.allowsCameraControl = true
        sceneView.isUserInteractionEnabled = true
        self.view.addSubview(sceneView)
    }
        
    private func setupParticles() {
        guard let stars = SCNParticleSystem(named: "StarsParticles.scnp", inDirectory: nil) else { return }
        stars.isLightingEnabled = false
                
        if sceneView != nil {
            sceneView.scene?.rootNode.addParticleSystem(stars)
        }
    }
    
    private func setupCamera() {
        self.cameraNode = SCNNode()
        cameraNode.camera = SCNCamera()
        cameraNode.position = SCNVector3(x: 0, y: 0, z: 5)
        sceneView.scene?.rootNode.addChildNode(cameraNode)
    }

    private func setupGlobe() {
        self.earthNode = EarthNode(radius: earthRadius, earthColor: earthColor, earthGlow: glowColor, earthReflection: reflectionColor)
        sceneView.scene?.rootNode.addChildNode(earthNode)
    }

    private func setupDotGeometry() {
        let textureMap = generateTextureMap(dots: dotCount, sphereRadius: CGFloat(earthRadius))

        let newYork = CLLocationCoordinate2D(latitude: 44.0682, longitude: -121.3153)
        let newYorkDot = closestDotPosition(to: newYork, in: textureMap)

        let dotColor = GenericColor(white: 1, alpha: 1)
        let oceanColor = GenericColor(cgColor: UIColor.systemRed.cgColor)
        let highlightColor = GenericColor(cgColor: UIColor.systemRed.cgColor)
        
        // threshold to determine if the pixel in the earth-dark.jpg represents terrain (0.03 represents rgb(7.65,7.65,7.65), which is almost black)
        let threshold: CGFloat = 0.03
        
        let dotGeometry = SCNSphere(radius: dotRadius)
        dotGeometry.firstMaterial?.diffuse.contents = dotColor
        dotGeometry.firstMaterial?.lightingModel = SCNMaterial.LightingModel.constant
        
        let highlightGeometry = SCNSphere(radius: dotRadius)
        highlightGeometry.firstMaterial?.diffuse.contents = highlightColor
        highlightGeometry.firstMaterial?.lightingModel = SCNMaterial.LightingModel.constant
        
        let oceanGeometry = SCNSphere(radius: dotRadius)
        oceanGeometry.firstMaterial?.diffuse.contents = oceanColor
        oceanGeometry.firstMaterial?.lightingModel = SCNMaterial.LightingModel.constant
        
        var positions = [SCNVector3]()
        var dotNodes = [SCNNode]()
        
        var highlightedNode: SCNNode? = nil
        
        for i in 0...textureMap.count - 1 {
            let u = textureMap[i].x
            let v = textureMap[i].y
            
            let pixelColor = self.getPixelColor(x: Int(u), y: Int(v))
            let isHighlight = u == newYorkDot.x && v == newYorkDot.y
            
            if (isHighlight) {
                let dotNode = SCNNode(geometry: highlightGeometry)
                dotNode.name = "NewYorkDot"
                dotNode.position = textureMap[i].position
                positions.append(dotNode.position)
                dotNodes.append(dotNode)
                
                print("myloc \(textureMap[i].position)")
                
                highlightedNode = dotNode
            } else if (pixelColor.red < threshold && pixelColor.green < threshold && pixelColor.blue < threshold) {
                let dotNode = SCNNode(geometry: dotGeometry)
                dotNode.name = "Other"
                dotNode.position = textureMap[i].position
                positions.append(dotNode.position)
                dotNodes.append(dotNode)
            }
        }
        
        DispatchQueue.main.async {
            let dotPositions = positions as NSArray
            let dotIndices = NSArray()
            let source = SCNGeometrySource(vertices: dotPositions as! [SCNVector3])
            let element = SCNGeometryElement(indices: dotIndices as! [Int32], primitiveType: .point)
            
            let pointCloud = SCNGeometry(sources: [source], elements: [element])
            
            let pointCloudNode = SCNNode(geometry: pointCloud)
            for dotNode in dotNodes {
                pointCloudNode.addChildNode(dotNode)
            }
     
            self.sceneView.scene?.rootNode.addChildNode(pointCloudNode)
            
            //performing gestures before this causes the bug
            DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
                if let highlightedNode = highlightedNode {
                    self.centerCameraOnDot(dotPosition: highlightedNode.position)
                }
            }
        }
   }
}