iOS：如何使节点围绕SceneKit中的特定轴旋转

Question

我是Swift编程和SceneKit框架的新手。我正在尝试构建Rubik的扭曲应用程序，到目前为止，我所获得的只是位于相机中心的链条。Rubik's twist chain

这是我实现的方式：

 var snake = [SCNNode]()
    var bounds_z = Float()
    var bounds_x = Float()
    var j = 0
    for i in 0...11{
        let piece_scene_1 = SCNScene(named: "piece.scnassets/piece.scn")!
        let piece_scene_2 = SCNScene(named: "piece.scnassets/piece.scn")!
        piece_scene_1.rootNode.childNodes[0].scale = SCNVector3(0.9, 0.9, 0.9)
        piece_scene_2.rootNode.childNodes[0].scale = SCNVector3(0.9, 0.9, 0.9)
        bounds_z = Float(2*(piece_scene_1.rootNode.childNodes[0].geometry?.boundingBox.max.z ?? 0.0))
        bounds_x = Float(2*(piece_scene_1.rootNode.childNodes[0].geometry?.boundingBox.min.x ?? 0.0))
        snake.append(piece_scene_1.rootNode.childNodes[0])
        snake.append(piece_scene_2.rootNode.childNodes[0])
        snake[j].name = "piece_\(j)"
        snake[j+1].name = "piece_\(j+1)"
        snake[j+1].rotation = SCNVector4(0, 1, 0, Float.pi)
        snake[j].position = SCNVector3(x: Float(i)*bounds_x,y: Float(0),z: Float(i)*bounds_z)
        snake[j+1].position = SCNVector3(x: Float(i)*bounds_x,y: Float(0),z: Float(i+1)*bounds_z)
        scene.rootNode.addChildNode(snake[j])
        scene.rootNode.addChildNode(snake[j+1])
        j+=2
    }
    cameraNode.look(at: snake[(snake.count/2)-1].position)

我的问题是，当点击时，使一组棋子旋转。我的想法是制作一个容器节点，在点击一个节点之前添加所有节点，然后围绕该点击面的法线轴（与该容器相邻）旋转容器。这是我的尝试：

@objc func handleTap(_ gestureRecognize: UIGestureRecognizer){

            let sceneView = self.view as! SCNView
            let p = gestureRecognize.location(in: sceneView)
            let hitResults = sceneView.hitTest(p, options: [:])
            if hitResults.count > 0 {
                // retrieved the first clicked object
                let result: SCNHitTestResult = hitResults[0]
                let container = SCNNode()
                let id_name = result.node.name
                let id_array = id_name?.components(separatedBy: CharacterSet.decimalDigits.inverted)
                  // add nodes to container
                    for item in id_array! {
                         if let id = Int(item){
                            for i in 0...id-1{
                                container.addChildNode(scene.rootNode.childNode(withName: "piece_\(i)", recursively: true)!)
                                }
                           // add container to scene
                            scene.rootNode.addChildNode(container)
                            // get container orientation
                            var GLKQuat = GLKQuaternionMake(container.orientation.x, container.orientation.y, container.orientation.z, container.orientation.w)
                            // get future orientation
                            let multiplier = GLKQuaternionMakeWithAngleAndAxis(Float.pi/2, 0, 0, 1)                        
                            // assign new orientation to container
                            GLKQuat = GLKQuaternionMultiply(GLKQuat, multiplier)
                            container.orientation = SCNQuaternion(GLKQuat.x, GLKQuat.y, GLKQuat.z, GLKQuat.w)           
                            // maintain childs position after rotation
                            for childnode in container.childNodes{
                                let child_transform = childnode.parent!.convertTransform(childnode.transform, to: scene.rootNode)
                                childnode.removeFromParentNode()
                                childnode.transform = child_transform
                                scene.rootNode.addChildNode(childnode)}
                           }
                         }
                       }
                     }

问题是，由于容器是scene.rootNode.child，将绕其z轴旋转像这样：Rubiks twist chain after rotation

Answer 1

围绕z轴的旋转是由这行代码引起的

let multiplier = GLKQuaternionMakeWithAngleAndAxis(Float.pi/2, 0, 0, 1) 

如果要绕另一个轴旋转，则必须指定x，y和z分量：from the Apple documentation