ARkit -- 平移

ARKit -- 矩阵变换

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代码测试一

• 下面我们添加一个动作手势.获取手势的移动距离,把这个移动距离作为节点的移动距离.
• 当然这里面只是为了简单的尝试.

添加属性 :  var node : SCNNode?
设置属性 :  node = sceneView.scene.rootNode.childNodes.first

extension ViewController {
    func addPanGes()  {
        let panGes = UIPanGestureRecognizer(target: self, action: #selector(ViewController.didPan(pan:)))
        sceneView.addGestureRecognizer(panGes)
    }
    
    @objc func didPan(pan : UIPanGestureRecognizer) {
        switch pan.state {
        case .changed:
            print(pan.translation(in: sceneView))
            let point = pan.translation(in: sceneView)
            guard let node = node else {return}
            node.position = SCNVector3Make(node.position.x + Float(point.x/10), //因为移动速度太快,所以除以10
                                           node.position.y - Float(point.y/10), //因为屏幕Y轴朝下,所以要用-号
                                           node.position.z )                    //这里暂时不考虑z轴
            pan.setTranslation(.zero, in: sceneView)
        default:
            break;
            
        }
    }
}

效果图

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代码测试二

extension ViewController {
    //动作手势
    func addPanGes()  {
        let panGes = UIPanGestureRecognizer(target: self, action: #selector(ViewController.didPan(pan:)))
        sceneView.addGestureRecognizer(panGes)
        
        let tapGes = UITapGestureRecognizer(target: self, action: #selector(ViewController.tapPan(tap:)))
        sceneView.addGestureRecognizer(tapGes)
    }

    //点击:放置AR对象位置
    @objc func tapPan(tap : UIPanGestureRecognizer) {
        let planeHitTestResults = sceneView.hitTest(tap.location(in: sceneView), types: .existingPlane)
        guard let result = planeHitTestResults.first else {return}
        
        guard let node = node else {return}
        node.position = SCNVector3Make(result.worldTransform.columns.3.x,
                                       result.worldTransform.columns.3.y,
                                       result.worldTransform.columns.3.z)
        
    }
    
    //平移 
    @objc func didPan(pan : UIPanGestureRecognizer) {
        switch pan.state {
        case .changed:
            guard let node = node else {return}
            let planeHitTestResults = sceneView.hitTest(pan.location(in: sceneView), types: .existingPlane)
            guard let result = planeHitTestResults.first else {return}
            let planeHitTestPosition = float3(x: result.worldTransform.columns.3.x,
                                              y: result.worldTransform.columns.3.y,
                                              z: result.worldTransform.columns.3.z)
            
            
            guard let cameraTransform = sceneView.session.currentFrame?.camera.transform else {return}
            let cameraWorldPosition = float3(x: cameraTransform.columns.3.x,
                                             y: cameraTransform.columns.3.y,
                                             z: cameraTransform.columns.3.z)
            
            let positionOffset = planeHitTestPosition - cameraWorldPosition
            node.simdPosition = cameraWorldPosition + positionOffset

        default:
            break;

        }
    }
}

效果图

• 这个效果和第一个不一样,这里面有Z轴的变化.有关于相机矩阵的内容. 这里面完全扣的是苹果官方源代码中的矩阵操作,我这里是简化了,矩阵内容无法讲解,研究了好久也脑补不上其中的细节原理.还有怎么才能通俗地去理解,先记住吧.
• 效果图里面有几块蓝色的平面,可以忽略,这个只是为了ARkit -- hitTest(_ point:, types:)做个演示.hitTest类型用的是existingPlane,所以只要检测到有平面,不考虑范围.

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关于平面的代码可以参考 :

一个Plane.swift文件

import UIKit
import SceneKit
import ARKit

class Plane: SCNNode {
    
    var anchor: ARPlaneAnchor!
    var planeGeometry: SCNPlane!
    
    init(withAnchor anchor: ARPlaneAnchor) {
        super.init()
        
        self.anchor = anchor
        planeGeometry = SCNPlane(width: CGFloat(anchor.extent.x), height: CGFloat(anchor.extent.z))
        
        // 相比把网格视觉化为灰色平面，我更喜欢用科幻风的颜色来渲染
        let material = SCNMaterial()
        let img = #imageLiteral(resourceName: "tron_grid")
        material.diffuse.contents = img
        material.lightingModel = .physicallyBased
        planeGeometry.materials = [material]
        
        let planeNode = SCNNode(geometry: planeGeometry)
        planeNode.position = SCNVector3Make(anchor.center.x, 0, anchor.center.z)
        
        // SceneKit 里的平面默认是垂直的，所以需要旋转90度来匹配 ARKit 中的平面
        planeNode.transform = SCNMatrix4MakeRotation(Float(-.pi / 2.0), 1.0, 0.0, 0.0)
        
        setTextureScale()
        addChildNode(planeNode)
        
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    func update(anchor: ARPlaneAnchor) {
        // 随着用户移动，平面 plane 的 范围 extend 和 位置 location 可能会更新。
        // 需要更新 3D 几何体来匹配 plane 的新参数。
        planeGeometry.width = CGFloat(anchor.extent.x);
        planeGeometry.height = CGFloat(anchor.extent.z);
        
        // plane 刚创建时中心点 center 为 0,0,0，node transform 包含了变换参数。
        // plane 更新后变换没变但 center 更新了，所以需要更新 3D 几何体的位置
        position = SCNVector3Make(anchor.center.x, 0, anchor.center.z)
        setTextureScale()
    }
    
    func setTextureScale() {
        let width = planeGeometry.width
        let height = planeGeometry.height
        
        // 平面的宽度/高度 width/height 更新时，我希望 tron grid material 覆盖整个平面，不断重复纹理。
        // 但如果网格小于 1 个单位，我不希望纹理挤在一起，所以这种情况下通过缩放更新纹理坐标并裁剪纹理
        let material = planeGeometry.materials.first
        material?.diffuse.contentsTransform = SCNMatrix4MakeScale(Float(width), Float(height), 1)
        material?.diffuse.wrapS = .repeat
        material?.diffuse.wrapT = .repeat
    }
}

ViewController.swift文件中

添加属性 : var planes = [UUID:Plane]() // 字典，存储场景中当前渲染的所有平面

代理方法 : 
 func renderer(_ renderer: SCNSceneRenderer, didAdd node: SCNNode, for anchor: ARAnchor) {
        guard let anchor = anchor as? ARPlaneAnchor else {
            return
        }
        let plane = Plane(withAnchor: anchor)
        planes[anchor.identifier] = plane
        node.addChildNode(plane)
    }
    
    func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
        guard let plane = planes[anchor.identifier] else {
            return
        }
        plane.update(anchor: anchor as! ARPlaneAnchor)
    }

    func renderer(_ renderer: SCNSceneRenderer, didRemove node: SCNNode, for anchor: ARAnchor) {
        planes.removeValue(forKey: anchor.identifier)
    }