我如何检测 ARAnchor 当前是否在相机中可见，我需要在相机 View 发生变化时进行测试。 当不在屏幕上时，我想在屏幕边缘放置指向 anchor 方向的箭头。我需要知道节点是位于视锥体的左侧还是右侧。

我现在正在这样做，但它说 pin 是可见的，而实际上它不可见，而且 X 值似乎不正确？也许渲染器截锥体与屏幕相机不匹配？

 var deltaTime = TimeInterval()

 public func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
        deltaTime = time - lastUpdateTime
        if deltaTime>1{

            if let annotation = annotationsByNode.first {

                let node = annotation.key.childNodes[0]

                if !renderer.isNode(node, insideFrustumOf: renderer.pointOfView!)
                {
                    print("Pin is not visible");
                }else {
                    print("Pin is visible");
                }
                let pnt = renderer.projectPoint(node.position)

                print("pos ", pnt.x, " ", renderer.pointOfView!.position)


            }
            lastUpdateTime = time
        }

    }

更新:代码用于显示节点是否可见，我如何判断节点相对于相机平截头体是向左还是向右？

更新2!正如 Bhanu Birani 建议的答案

let screenWidth = UIScreen.main.bounds.width
let screenHeight = UIScreen.main.bounds.height
let leftPoint = CGPoint(x: 0, y: screenHeight/2)
let rightPoint = CGPoint(x: screenWidth,y: screenHeight/2)

let leftWorldPos = renderer.unprojectPoint(SCNVector3(leftPoint.x,leftPoint.y,0))
let rightWorldPos = renderer.unprojectPoint(SCNVector3(rightPoint.x,rightPoint.y,0))
let distanceLeft = node.position - leftWorldPos
let distanceRight = node.position - rightWorldPos
let dir = (isVisible) ? "visible" : ( (distanceLeft.x<distanceRight.x) ? "left" : "right")

我终于让它工作了，它使用了屏幕左右两侧的 Bhanu Birani 的想法，但我得到了不同的世界位置，unProjectPoint 并且还得到了距离的标量值，我比较它以获得左/右方向.也许有更好的方法，但它对我有用

public func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
        deltaTime = time - lastUpdateTime
        if deltaTime>0.25{

            if let annotation = annotationsByNode.first {
                guard let pointOfView = renderer.pointOfView else {return}
                let node = annotation.key.childNodes[0]
                let isVisible = renderer.isNode(node, insideFrustumOf: pointOfView)

                let screenWidth = UIScreen.main.bounds.width
                let screenHeight = UIScreen.main.bounds.height
                let leftPoint = CGPoint(x: 0, y: screenHeight/2)
                let rightPoint = CGPoint(x: screenWidth,y: screenHeight/2)

                let leftWorldPos = renderer.unprojectPoint(SCNVector3(leftPoint.x, leftPoint.y,0))
                let rightWorldPos =  renderer.unprojectPoint(SCNVector3(rightPoint.x, rightPoint.y,0))
                let distanceLeft = node.worldPosition.distance(vector: leftWorldPos)
                let distanceRight = node.worldPosition.distance(vector: rightWorldPos)

                //let pnt = renderer.projectPoint(node.worldPosition)
                //guard let pnt = renderer.pointOfView!.convertPosition(node.position, to: nil) else {return}

                let dir = (isVisible) ? "visible" : ( (distanceLeft<distanceRight) ? "left" : "right")
                print("dir" , dir, " ", leftWorldPos , " ", rightWorldPos)
                lastDir=dir
                delegate?.nodePosition?(node:node, pos: dir)
            }else {
               delegate?.nodePosition?(node:nil, pos: lastDir )
            }
            lastUpdateTime = time
        }

extension SCNVector3
{

    /**
     * Returns the length (magnitude) of the vector described by the SCNVector3
     */
    func length() -> Float {
        return sqrtf(x*x + y*y + z*z)
    }

    /**
     * Calculates the distance between two SCNVector3. Pythagoras!
     */
    func distance(vector: SCNVector3) -> Float {
        return (self - vector).length()
    }


}

最佳答案

从以下屏幕位置转换光线:

• leftPoint = CGPoint(0, screenHeight/2)(屏幕左中)
• rightPoint = CGPoint(screenWidth, screenHeight/2)(屏幕右中)

将 CGPoint 转换为世界位置:

• leftWorldPos = convertCGPointToWorldPosition(leftPoint)
• rightWorldPos = convertCGPointToWorldPosition(rightPoint)

计算节点到两个世界位置的距离:

• distanceLeft = node.position - leftWorldPos
• distanceRight = node.position - rightWorldPos

比较距离以找到到节点的最短距离。用最短距离向量为物体定位方向箭头。

这是来自 tsukimi 的代码，用于检查对象是在屏幕的右侧还是左侧:

public func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) {
        deltaTime = time - lastUpdateTime
        if deltaTime>0.25{

            if let annotation = annotationsByNode.first {
                guard let pointOfView = renderer.pointOfView else {return}
                let node = annotation.key.childNodes[0]
                let isVisible = renderer.isNode(node, insideFrustumOf: pointOfView)

                let screenWidth = UIScreen.main.bounds.width
                let screenHeight = UIScreen.main.bounds.height
                let leftPoint = CGPoint(x: 0, y: screenHeight/2)
                let rightPoint = CGPoint(x: screenWidth,y: screenHeight/2)

                let leftWorldPos = renderer.unprojectPoint(SCNVector3(leftPoint.x, leftPoint.y,0))
                let rightWorldPos =  renderer.unprojectPoint(SCNVector3(rightPoint.x, rightPoint.y,0))
                let distanceLeft = node.worldPosition.distance(vector: leftWorldPos)
                let distanceRight = node.worldPosition.distance(vector: rightWorldPos)

                //let pnt = renderer.projectPoint(node.worldPosition)
                //guard let pnt = renderer.pointOfView!.convertPosition(node.position, to: nil) else {return}

                let dir = (isVisible) ? "visible" : ( (distanceLeft<distanceRight) ? "left" : "right")
                print("dir" , dir, " ", leftWorldPos , " ", rightWorldPos)
                lastDir=dir
                delegate?.nodePosition?(node:node, pos: dir)
            }else {
               delegate?.nodePosition?(node:nil, pos: lastDir )
            }
            lastUpdateTime = time
        }

下面是帮助对vector进行操作的类

extension SCNVector3 {

    init(_ vec: vector_float3) {
        self.x = vec.x
        self.y = vec.y
        self.z = vec.z
    }

    func length() -> Float {
        return sqrtf(x * x + y * y + z * z)
    }

    mutating func setLength(_ length: Float) {
        self.normalize()
        self *= length
    }

    mutating func setMaximumLength(_ maxLength: Float) {
        if self.length() <= maxLength {
            return
        } else {
            self.normalize()
            self *= maxLength
        }
    }

    mutating func normalize() {
        self = self.normalized()
    }

    func normalized() -> SCNVector3 {
        if self.length() == 0 {
            return self
        }

        return self / self.length()
    }

    static func positionFromTransform(_ transform: matrix_float4x4) -> SCNVector3 {
        return SCNVector3Make(transform.columns.3.x, transform.columns.3.y, transform.columns.3.z)
    }

    func friendlyString() -> String {
        return "(\(String(format: "%.2f", x)), \(String(format: "%.2f", y)), \(String(format: "%.2f", z)))"
    }

    func dot(_ vec: SCNVector3) -> Float {
        return (self.x * vec.x) + (self.y * vec.y) + (self.z * vec.z)
    }

    func cross(_ vec: SCNVector3) -> SCNVector3 {
        return SCNVector3(self.y * vec.z - self.z * vec.y, self.z * vec.x - self.x * vec.z, self.x * vec.y - self.y * vec.x)
    }
}




extension SCNVector3{
    func distance(receiver:SCNVector3) -> Float{
        let xd = receiver.x - self.x
        let yd = receiver.y - self.y
        let zd = receiver.z - self.z
        let distance = Float(sqrt(xd * xd + yd * yd + zd * zd))

        if (distance < 0){
            return (distance * -1)
        } else {
            return (distance)
        }
    }
}

这里是将点击位置或任何 CGPoint 转换为世界转换的代码片段。

@objc func handleTap(_ sender: UITapGestureRecognizer) {

    // Take the screen space tap coordinates and pass them to the hitTest method on the ARSCNView instance
    let tapPoint = sender.location(in: sceneView)
    let result = sceneView.hitTest(tapPoint, types: ARHitTestResult.ResultType.existingPlaneUsingExtent)

    // If the intersection ray passes through any plane geometry they will be returned, with the planes
    // ordered by distance from the camera
    if (result.count > 0) {

        // If there are multiple hits, just pick the closest plane
        if let hitResult = result.first {
            let finalPosition = SCNVector3Make(hitResult.worldTransform.columns.3.x + insertionXOffset,
                                                       hitResult.worldTransform.columns.3.y + insertionYOffset,
                                                       hitResult.worldTransform.columns.3.z + insertionZOffset
                    );
        }
    }
}

以下是在没有找到平面的情况下获取 HitTest 结果的代码。

// check what nodes are tapped
let p = gestureRecognize.location(in: scnView)
let hitResults = scnView.hitTest(p, options: [:])
// check that we clicked on at least one object
if hitResults.count > 0 {
    // retrieved the first clicked object
    let result = hitResults[0] 
}

关于swift - arkit anchor 或节点在相机中可见，位于截锥体的左侧或右侧，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/46539121/