Question

我正在使用3D模型开发ARKit应用程序。为此，我使用了3D模型并添加了用于移动，旋转和缩放3D模型的手势。

现在我只面临1个问题，但是我不确定这个问题与什么有关。 3d模型是否存在问题，或者我的程序中是否缺少任何内容。

问题是我正在使用的3D模型，显示的非常大并超出了屏幕。我正在尝试缩小尺寸，但尺寸很大。

这是我的代码：

@IBOutlet var mySceneView: ARSCNView!
var selectedNode = SCNNode()
var prevLoc = CGPoint()
var touchCount : Int = 0

override func viewDidLoad() {
    super.viewDidLoad()
    self.lblTitle.text = self.sceneTitle
    let mySCN = SCNScene.init(named: "art.scnassets/\(self.sceneImagename).scn")!
    self.mySceneView.scene = mySCN

    let cameraNode = SCNNode()
    cameraNode.camera = SCNCamera()
    cameraNode.position = SCNVector3Make(0, 0, 0)
    self.mySceneView.scene.rootNode.addChildNode(cameraNode)
    self.mySceneView.allowsCameraControl = true
    self.mySceneView.autoenablesDefaultLighting = true

    let tapGesture = UITapGestureRecognizer(target: self, action: #selector(detailPage.doHandleTap(_:)))
    let panGesture = UIPanGestureRecognizer(target: self, action: #selector(detailPage.doHandlePan(_:)))
    let gesturesArray = NSMutableArray()
    gesturesArray.add(tapGesture)
    gesturesArray.add(panGesture)
    gesturesArray.addObjects(from: self.mySceneView.gestureRecognizers!)
    self.mySceneView.gestureRecognizers = (gesturesArray as! [UIGestureRecognizer])
}

//MARK:- Handle Gesture
@objc func doHandlePan(_ sender: UIPanGestureRecognizer) {
    var delta = sender.translation(in: self.view)
    let loc = sender.location(in: self.view)
    if sender.state == .began {
        self.prevLoc = loc
        self.touchCount = sender.numberOfTouches
    } else if sender.state == .changed {
        delta = CGPoint(x: loc.x - prevLoc.x, y: loc.y - prevLoc.y)
        prevLoc = loc
        if self.touchCount != sender.numberOfTouches {
            return
        }

        var rotMat = SCNMatrix4()
        if touchCount == 2 {
            rotMat = SCNMatrix4MakeTranslation(Float(delta.x * 0.025), Float(delta.y * -0.025), 0)
        } else {
            let rotMatX = SCNMatrix4Rotate(SCNMatrix4Identity, Float((1.0/100) * delta.y), 1, 0, 0)
            let rotMatY = SCNMatrix4Rotate(SCNMatrix4Identity, Float((1.0/100) * delta.x), 0, 1, 0)
            rotMat = SCNMatrix4Mult(rotMatX, rotMatY)
        }

        let transMat = SCNMatrix4MakeTranslation(selectedNode.position.x, selectedNode.position.y, selectedNode.position.z)
        selectedNode.transform = SCNMatrix4Mult(selectedNode.transform, SCNMatrix4Invert(transMat))

        let parentNodeTransMat = SCNMatrix4MakeTranslation((selectedNode.parent?.worldPosition.x)!, (selectedNode.parent?.worldPosition.y)!, (selectedNode.parent?.worldPosition.z)!)
        let parentNodeMatWOTrans = SCNMatrix4Mult(selectedNode.parent!.worldTransform, SCNMatrix4Invert(parentNodeTransMat))
        selectedNode.transform = SCNMatrix4Mult(selectedNode.transform, parentNodeMatWOTrans)

        let camorbitNodeTransMat = SCNMatrix4MakeTranslation((self.mySceneView.pointOfView?.worldPosition.x)!, (self.mySceneView.pointOfView?.worldPosition.y)!, (self.mySceneView.pointOfView?.worldPosition.z)!)
        let camorbitNodeMatWOTrans = SCNMatrix4Mult(self.mySceneView.pointOfView!.worldTransform, SCNMatrix4Invert(camorbitNodeTransMat))
        selectedNode.transform = SCNMatrix4Mult(selectedNode.transform, SCNMatrix4Invert(camorbitNodeMatWOTrans))
        selectedNode.transform = SCNMatrix4Mult(selectedNode.transform, rotMat)

        selectedNode.transform = SCNMatrix4Mult(selectedNode.transform, camorbitNodeMatWOTrans)
        selectedNode.transform = SCNMatrix4Mult(selectedNode.transform, SCNMatrix4Invert(parentNodeMatWOTrans))
        selectedNode.transform = SCNMatrix4Mult(selectedNode.transform, transMat)
    }
}

@objc func doHandleTap(_ sender: UITapGestureRecognizer) {
    let p = sender.location(in: self.mySceneView)
    var hitResults = self.mySceneView.hitTest(p, options: nil)

    if (p.x > self.mySceneView.frame.size.width-100 || p.y < 100) {
        self.mySceneView.allowsCameraControl = !self.mySceneView.allowsCameraControl
    }

    if hitResults.count > 0 {
        let result = hitResults[0]
        let material = result.node.geometry?.firstMaterial
        selectedNode = result.node

        SCNTransaction.begin()
        SCNTransaction.animationDuration = 0.3

        SCNTransaction.completionBlock = {
            SCNTransaction.begin()
            SCNTransaction.animationDuration = 0.3
            SCNTransaction.commit()
        }
        material?.emission.contents = UIColor.white
        SCNTransaction.commit()
    }
}

我的问题是：

我们可以在屏幕中心设置适合屏幕尺寸的3d对象模型Aspect的任何大小吗？请建议是否有办法。

任何指导或建议将不胜感激。

Answer 1

您需要使用getBoundingSphereCenter来获取边界球的大小，然后可以将其投影到屏幕上。或者，获取该半径与场景套件相机和对象位置之间的距离之比。这样，您将知道对象在屏幕上看起来有多大。要缩小比例，您只需设置对象的scale属性即可。

第二部分，您可以使用projectPoint。

Answer 2

我处理此问题的方法是确保3D模型始终具有固定大小。

例如，如果3D模型是小杯子还是大房子，我可以确保它在场景的坐标空间上始终具有25 cm的宽度（同时保持x y z之比）。

您可以像这样计算节点边界框的宽度：

let mySCN = SCNScene(named: "art.scnassets/\(self.sceneImagename).scn")!

let minX = mySCN.rootNode.boundingBox.min.x
let maxX = mySCN.rootNode.boundingBox.max.x

// change 0.25 to whatever you need
// this value is in meters
let scaleValue = 0.25 / abs(minX - maxX)

// scale all axes of the node using `scaleValue`
// this maintains ratios and does not stretch the model
mySCN.rootNode.scale = SCNVector3(scaleValue, scaleValue, scaleValue)

self.mySceneView.scene = mySCN

您还可以使用边界框的y或z值，根据高度或深度计算比例值。

ARSCNView 3d对象宽高比适合

2 个答案: