我有一个SCNCamera场景设置，可以围绕一个对象旋转。

限制相机围绕物体旋转的最佳方式是什么？

示例：除了能够围绕整个球体旋转之外，我如何将旋转限制为单个半球？

我的第一个尝试是查看.allowsCameraControl是否存在任何限制。找不到任何东西。

然后，我尝试使用c＃Unity：鼠标轨道脚本，不走运。

关于如何解决或解决此问题的一些指示将非常有用。

var lastWidthRatio: Float = 0
var lastHeightRatio: Float = 0

let camera = SCNCamera()
let cameraNode = SCNNode()
let cameraOrbit = SCNNode()

override func viewDidLoad() {
    super.viewDidLoad()

    // create a new scene
    let scene = SCNScene(named: "art.scnassets/ship.scn")!

    // create and add a camera to the scene

    camera.usesOrthographicProjection = true
    camera.orthographicScale = 9
    camera.zNear = 0
    camera.zFar = 100

    cameraNode.position = SCNVector3(x: 0, y: 0, z: 50)
    cameraNode.camera = camera

    cameraOrbit.addChildNode(cameraNode)
    scene.rootNode.addChildNode(cameraOrbit)

    // retrieve the ship node
    let ship = scene.rootNode.childNodeWithName("ship", recursively: true)!

    // retrieve the SCNView
    let scnView = self.view as! SCNView

    // set the scene to the view
    scnView.scene = scene

    // add a tap gesture recognizer
    let gesture = UIPanGestureRecognizer(target: self, action: "panDetected:");
    scnView.addGestureRecognizer(gesture);
}


func panDetected(sender: UIPanGestureRecognizer) {
    let translation = sender.translationInView(sender.view!)
    let widthRatio = Float(translation.x) / Float(sender.view!.frame.size.width) + lastWidthRatio
    let heightRatio = Float(translation.y) / Float(sender.view!.frame.size.height) + lastHeightRatio
    self.cameraOrbit.eulerAngles.y = Float(-2 * M_PI) * widthRatio
    self.cameraOrbit.eulerAngles.x = Float(-M_PI) * heightRatio

    print(Float(-2 * M_PI) * widthRatio)
    if (sender.state == .Ended) {
        lastWidthRatio = widthRatio % 1
        lastHeightRatio = heightRatio % 1
    }
}