SCNCamera 在 SCNScene 中的默认位置

问题描述

我想我没有完全理解 SCNCamera 应该如何工作。

所以我有以下代码：

import SwiftUI
import SceneKit

struct ContentView: View {
    let scene = SCNScene(named: "Earth.usdz")
    var cameraNode: SCNNode? {
        let cameraNode = SCNNode()
        cameraNode.camera = SCNCamera()
        cameraNode.position = SCNVector3(x: 0,y: 0,z: 2)
        return cameraNode
    }
    var body: some View {
        vstack {
            SceneView(
                scene: scene,pointOfView: cameraNode,options: [
                    .allowsCameraControl,.autoenablesDefaultLighting
                ]
            )
            .frame(width: UIScreen.main.bounds.width,height: UIScreen.main.bounds.height/2)
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

删除或添加 pointOfView: cameraNode 会导致：

无

与

我假设有一些默认的相机位置（也许还有其他属性？）？我怎么看那些是什么？如何取消地球反转？

我想在不设置 pointOfView 的情况下或多或少地模仿我得到的结果，然后以编程方式旋转地球。

谢谢大家！

解决方法

如果您创建一个相机类，关闭allowsCameraControl，并取消PointOfView 交易，那么您的lookAtConstraint 将指向地球节点，您可以通过为其中任何一个设置.position 来调整距离。这是一个让你专注于地球的例子 - strafe 只是让你知道你可以用相机节点做什么。旋转地球不会影响相机节点。你可以在那里做任何你想做的旋转，相机仍然会指向地球。

class Camera
{
    var cameraEye = SCNNode()
    var cameraFocus = SCNNode()
        
    var centerX: Int = 100
    var strafeDelta: Float = 0.8
    var zoomLevel: Int = 35
    var zoomLevelMax: Int = 35              // Max number of zoom levels
    
    //********************************************************************
    init()
    {
        cameraEye.name = "Camera Eye"
        cameraFocus.name = "Camera Focus"
        
        cameraFocus.isHidden = true
        cameraFocus.position  =  SCNVector3(x: 0,y: 0,z: 0)
        
        cameraEye.camera = SCNCamera()
        cameraEye.constraints = []
        cameraEye.position = SCNVector3(x: 0,y: 15,z: 0.1)
        
        let vConstraint = SCNLookAtConstraint(target: cameraFocus)
        vConstraint.isGimbalLockEnabled = true
        cameraEye.constraints = [vConstraint]
    }
    //********************************************************************
    func reset()
    {
        centerX = 100
        cameraFocus.position  =  SCNVector3(x: 0,z: 0)
        cameraEye.constraints = []
        cameraEye.position = SCNVector3(x: 0,y: 32,z: 0.1)
        cameraFocus.position = SCNVector3Make(0,0)
        
        let vConstraint = SCNLookAtConstraint(target: cameraFocus)
        vConstraint.isGimbalLockEnabled = true
        cameraEye.constraints = [vConstraint]
    }
    //********************************************************************
    func strafeRight()
    {
        if(centerX + 1 < 112)
        {
            centerX += 1
            cameraEye.position.x += strafeDelta
            cameraFocus.position.x += strafeDelta
        }
    }
    //********************************************************************
    func strafeLeft()
    {
        if(centerX - 1 > 90)
        {
            centerX -= 1
            cameraEye.position.x -= strafeDelta
            cameraFocus.position.x -= strafeDelta
        }
    }
    //********************************************************************
}