SceneKit：通過平移手勢將相機移向其朝向

Question

我在我的SceneKit游戲中設置了一些自定義相機控件。 我在根據相機的y歐拉角進行自動平移手勢時遇到問題。 我具有的平移手勢通過在x和z軸上平移相機（通過使用手勢平移）來工作。問題是，盡管相機旋轉，但相機仍將繼續在x和z軸上平移。 我想要它，以便相機在其面向的軸上平移。

這是我用來平移/旋轉的手勢：

平移：

var previousTranslation = SCNVector3(x: 0.0,y: 15,z: 0.0)
var lastWidthRatio:Float = 0
var angle:Float = 0

@objc func pan(gesture: UIPanGestureRecognizer) {
    gesture.minimumNumberOfTouches = 1
    gesture.maximumNumberOfTouches = 1
    if gesture.numberOfTouches == 1 {
        let view = self.view as! SCNView
        let node = view.scene!.rootNode.childNode(withName: "Node", recursively: false)
        let secondNode =  view.scene!.rootNode.childNode(withName: "CameraHandler", recursively: false)
        let translation = gesture.translation(in: view)

        let constant: Float = 30.0
        angle = secondNode!.eulerAngles.y
        //these were the previous values I was using to handle panning, they worked but provided really jittery movement. You can change the direction they rotate by multiplying the sine/cosine .pi values by any integer.
        //var translateX = Float(translation.y) * sin(.pi) / cos(.pi) - Float(translation.x) * cos(.pi)
        //var translateY = Float(translation.y) * cos(.pi) / cos(.pi) + Float(translation.x) * sin(.pi)

        //these ones work a lot smoother
        var translateX = Float(translation.x) * Float(Double.pi / 180)
        var translateY = Float(translation.y) * Float(Double.pi / 180)
        translateX = translateX * constant
        translateY = translateY * constant

        switch gesture.state {
        case .began:
            previousTranslation = node!.position
            break;
        case .changed:
            node!.position = SCNVector3Make((previousTranslation.x + translateX), previousTranslation.y, (previousTranslation.z + translateY))
            break
        default: break
        }
    }
}

回轉：

@objc func rotate(gesture: UIPanGestureRecognizer) {
    gesture.minimumNumberOfTouches = 2
    gesture.maximumNumberOfTouches = 2
    if gesture.numberOfTouches == 2 {
        let view = self.view as! SCNView
        let node = view.scene!.rootNode.childNode(withName: "CameraHandler", recursively: false)
        let translate = gesture.translation(in: view)

        var widthRatio:Float = 0

        widthRatio = Float(translate.x / 10) * Float(Double.pi / 180)

        switch gesture.state {
        case .began:
            lastWidthRatio = node!.eulerAngles.y
            break
        case .changed:
            node!.eulerAngles.y = lastWidthRatio + widthRatio
            print(node!.eulerAngles.y)
            break
        default: break
        }
    }
}

CameraHandler節點是Camera節點的父節點。 一切正常，只是不像我想要的那樣工作。 希望這很清楚，讓你們理解。

Answer 1

在目標C中，關鍵部分是最后三行，尤其是最后一行中矩陣的乘法順序（導致移動發生在局部空間中）。 如果切換了Transmat和Cammat，它將像現在一樣（在世界空間中移動）再次表現。 重構部分僅適用於我可能同時使用透視相機和正交相機的特定情況。

-(void)panCamera :(CGPoint)location {

CGFloat dx = _prevlocation.x - location.x;
CGFloat dy = location.y - _prevlocation.y;
_prevlocation = location;

//refactor dx and dy based on camera distance or orthoscale
if (cameraNode.camera.usesOrthographicProjection) {
    dx = dx / 416 * cameraNode.camera.orthographicScale;
    dy = dy / 416 * cameraNode.camera.orthographicScale;
} else {
    dx = dx / 720 * cameraNode.position.z;
    dy = dy / 720 * cameraNode.position.z;
}

SCNMatrix4 cammat = self.cameraNode.transform;
SCNMatrix4 transmat = SCNMatrix4MakeTranslation(dx, 0, dy);
self.cameraNode.transform = SCNMatrix4Mult(transmat, cammat);

}

Answer 2

根據Xartec的回答，我弄清楚了。 我將其翻譯為快速內容，並對其進行了改裝，使其可以滿足我的需求。 我對它並不真正滿意，因為運動不平穩。 我將在今天晚些時候進行平滑處理。

平移手勢：此手勢沿旋轉相機的方向在場景周圍平移相機父節點。 它的工作原理與我想要的完全一樣。

@objc func pan(gesture: UIPanGestureRecognizer) {
    gesture.minimumNumberOfTouches = 1
    gesture.maximumNumberOfTouches = 1
    if gesture.numberOfTouches == 1 {
        let view = self.view as! SCNView
        let node = view.scene!.rootNode.childNode(withName: "CameraHandler", recursively: false)
        let translation = gesture.translation(in: view)

        var dx = previousTranslation.x - translation.x
        var dy = previousTranslation.y - translation.y

        dx = dx / 100
        dy = dy / 100
        print(dx,dy)

        let cammat = node!.transform
        let transmat = SCNMatrix4MakeTranslation(Float(dx), 0, Float(dy))

        switch gesture.state {
        case .began:
            previousTranslation = translation
            break;
        case .changed:
            node!.transform = SCNMatrix4Mult(transmat, cammat)
            break
        default: break
        }
    }
}

旋轉手勢：此手勢用兩個手指旋轉相機。

@objc func rotate(gesture: UIPanGestureRecognizer) {
    gesture.minimumNumberOfTouches = 2
    gesture.maximumNumberOfTouches = 2
    if gesture.numberOfTouches == 2 {
        let view = self.view as! SCNView
        let node = view.scene!.rootNode.childNode(withName: "CameraHandler", recursively: false)
        let translate = gesture.translation(in: view)

        var widthRatio:Float = 0
        widthRatio = Float(translate.x / 10) * Float(Double.pi / 180)

        switch gesture.state {
        case .began:
            lastWidthRatio = node!.eulerAngles.y
            break
        case .changed:
            node!.eulerAngles.y = lastWidthRatio + widthRatio
            break
        default: break
        }
    }
}

為了獲得與我相同的功能，您需要將cameraNode附加到父節點。 像這樣：

    //create and add a camera to the scene
    let cameraNode = SCNNode()

    //cameraHandler is declared outside viewDidLoad. 
    let cameraHandler = SCNNode()

    cameraNode.camera = SCNCamera()
    cameraNode.name = "Camera"
    cameraNode.position = SCNVector3(x: 0.0,y: 10.0,z: 20.0)
    //This euler angle only rotates the camera downward a little bit. It is not neccessary 
    cameraNode.eulerAngles = SCNVector3(x: -0.6, y: 0, z: 0)

    cameraHandler.addChildNode(cameraNode)
    cameraHandler.name = "CameraHandler"

    scene.rootNode.addChildNode(cameraHandler)