如何通過在屏幕上拖動手指來更改相機位置 - Swift

Question

我正在嘗試學習 ARKIT 並制作一個小型演示應用程序來繪制 3D。 以下是我寫的代碼，目前沒有問題：

import UIKit
import ARKit

class ViewController: UIViewController, ARSCNViewDelegate {

    @IBOutlet weak var sceneView: ARSCNView!

    @IBOutlet weak var DRAW: UIButton!
    @IBOutlet weak var DEL: UIButton!

    let config = ARWorldTrackingConfiguration()

    override func viewDidLoad() {
        super.viewDidLoad()

        self.sceneView.session.run(config)
        self.sceneView.delegate = self
    }

    func renderer(_ renderer: SCNSceneRenderer, willRenderScene scene: SCNScene, atTime time: TimeInterval) {

        guard let pointOfView = sceneView.pointOfView else {return}
        let transform = pointOfView.transform
        let cameraOrientation = SCNVector3(-transform.m31,-transform.m32,-transform.m33)
        let cameraLocation = SCNVector3(transform.m41,transform.m42,transform.m43)
        let cameraCurrentPosition = cameraOrientation + cameraLocation

        DispatchQueue.main.async {

            if (self.DRAW.isTouchInside){
                let sphereNode  = SCNNode(geometry: SCNSphere(radius: 0.02))
                    sphereNode.position = cameraCurrentPosition
                    self.sceneView.scene.rootNode.addChildNode(sphereNode)
                    sphereNode.geometry?.firstMaterial?.diffuse.contents = UIColor.red
                    print("RED Button is Pressed")
                }else if (self.DEL.isTouchInside){
                    self.sceneView.scene.rootNode.enumerateChildNodes{
                    (node, stop) in
                    node.removeFromParentNode()
                    }
                }else{
                    let pointer = SCNNode(geometry: SCNSphere(radius: 0.01))
                    pointer.name = "pointer"
                    pointer.position = cameraCurrentPosition
                    self.sceneView.scene.rootNode.enumerateChildNodes({(node,_) in
                        if node.name == "pointer"{
                            node.removeFromParentNode()
                        }
                    })
                     self.sceneView.scene.rootNode.addChildNode(pointer)
                    pointer.geometry?.firstMaterial?.diffuse.contents = UIColor.purple
                }
        }
    }
}

func +(left:SCNVector3,right:SCNVector3) -> SCNVector3 {
    return SCNVector3Make(left.x + right.x, left.y + right.y, left.z + right.z)
}

如您所見，我設置了場景並對其進行了配置，我創建了一個在按下時進行繪制的按鈕、一個位於場景中心的指針（或取景器）以及一個用於刪除插入節點的按鈕。

現在我希望能夠將 cameraCurrentPosition 移動到與中心不同的點：如果可能，我想通過在屏幕上觸摸手指的位置來移動它。 如果可能的話，有人可以幫我寫代碼嗎？

Answer 1

一般來說，您不能以編程方式在 ARSCN 內移動相機，相機變換是設備相對於虛擬場景的物理位置。

話雖如此，您可以將用戶觸摸繪制到屏幕的一種方法是在您的視圖控制器中使用touchesMoved方法。

var touchRoots: [SCNNode] = [] // list of root nodes for each set of touches drawn

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    // get the initial touch event
    if let touch = touches.first {
        guard let pointOfView = self.sceneView.pointOfView else { return }
        let transform = pointOfView.transform // transformation matrix
        let orientation = SCNVector3(-transform.m31, -transform.m32, -transform.m33) // camera rotation
        let location = SCNVector3(transform.m41, transform.m42, transform.m43) // location of camera frustum
        let currentPostionOfCamera = orientation + location // center of frustum in world space
        DispatchQueue.main.async {
            let touchRootNode : SCNNode = SCNNode() // create an empty node to serve as our root for the incoming points
            touchRootNode.position = currentPostionOfCamera // place the root node ad the center of the camera's frustum
            touchRootNode.scale = SCNVector3(1.25, 1.25, 1.25)// touches projected in Z will appear smaller than expected - increase scale of root node to compensate
            guard let sceneView = self.sceneView else { return }
            sceneView.scene.rootNode.addChildNode(touchRootNode) // add the root node to the scene
            let constraint = SCNLookAtConstraint(target: self.sceneView.pointOfView) // force root node to always face the camera
            constraint.isGimbalLockEnabled = true // enable gimbal locking to avoid issues with rotations from LookAtConstraint
            touchRootNode.constraints = [constraint] // apply LookAtConstraint

            self.touchRoots.append(touchRootNode)
        }
    }
}

override func func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    if let touch = touches.first {
        let translation = touch.location(in: self.view)
        let translationFromCenter = CGPoint(x: translation.x - (0.5 * self.view.frame.width), y: translation.y - (0.5 * self.view.frame.height))

        // add nodes using the main thread
        DispatchQueue.main.async {
            guard let touchRootNode = self.touchRoots.last else { return }
            let sphereNode : SCNNode = SCNNode(geometry: SCNSphere(radius: 0.015))
            sphereNode.position = SCNVector3(-1*Float(translationFromCenter.x/1000), -1*Float(translationFromCenter.y/1000), 0)
            sphereNode.geometry?.firstMaterial?.diffuse.contents = UIColor.white
            touchRootNode.addChildNode(sphereNode)  // add point to the active root
        }
    }
}

注意：解決方案僅處理單點觸控，但擴展示例以添加多點觸控支持很簡單。