无法为某些情况创建圆柱体 - Arkit

Question

我有两个向量作为输入，我试图在它们之间创建一个圆柱体。但这失败了，当我的点的 x 和 z 坐标相同而 y 坐标不同时

我有以下功能：

func buildLineInTwoPointsWithRotation(from startPoint: SCNVector3,
                                          to endPoint: SCNVector3,
                                          radius: CGFloat,
                                          color: UIColor) -> SCNNode {
        let w = SCNVector3(x: endPoint.x-startPoint.x,
                           y: endPoint.y-startPoint.y,
                           z: endPoint.z-startPoint.z)
        let l = CGFloat(sqrt(w.x * w.x + w.y * w.y + w.z * w.z))

        if l == 0.0 {
            // two points together.
            let sphere = SCNSphere(radius: radius)
            sphere.firstMaterial?.diffuse.contents = color
            self.geometry = sphere
            self.position = startPoint
            return self

        }

        let cyl = SCNCylinder(radius: radius, height: l)
        cyl.firstMaterial?.diffuse.contents = color

        self.geometry = cyl

        //original vector of cylinder above 0,0,0
        let ov = SCNVector3(0, l/2.0,0)
        //target vector, in new coordination
        let nv = SCNVector3((endPoint.x - startPoint.x)/2.0, (endPoint.y - startPoint.y)/2.0,
                            (endPoint.z-startPoint.z)/2.0)

        // axis between two vector
        let av = SCNVector3( (ov.x + nv.x)/2.0, (ov.y+nv.y)/2.0, (ov.z+nv.z)/2.0)

        //normalized axis vector
        let av_normalized = normalizeVector(av)
        let q0 = Float(0.0) //cos(angel/2), angle is always 180 or M_PI
        let q1 = Float(av_normalized.x) // x' * sin(angle/2)
        let q2 = Float(av_normalized.y) // y' * sin(angle/2)
        let q3 = Float(av_normalized.z) // z' * sin(angle/2)

        let r_m11 = q0 * q0 + q1 * q1 - q2 * q2 - q3 * q3
        let r_m12 = 2 * q1 * q2 + 2 * q0 * q3
        let r_m13 = 2 * q1 * q3 - 2 * q0 * q2
        let r_m21 = 2 * q1 * q2 - 2 * q0 * q3
        let r_m22 = q0 * q0 - q1 * q1 + q2 * q2 - q3 * q3
        let r_m23 = 2 * q2 * q3 + 2 * q0 * q1
        let r_m31 = 2 * q1 * q3 + 2 * q0 * q2
        let r_m32 = 2 * q2 * q3 - 2 * q0 * q1
        let r_m33 = q0 * q0 - q1 * q1 - q2 * q2 + q3 * q3

        self.transform.m11 = r_m11
        self.transform.m12 = r_m12
        self.transform.m13 = r_m13
        self.transform.m14 = 0.0

        self.transform.m21 = r_m21
        self.transform.m22 = r_m22
        self.transform.m23 = r_m23
        self.transform.m24 = 0.0

        self.transform.m31 = r_m31
        self.transform.m32 = r_m32
        self.transform.m33 = r_m33
        self.transform.m34 = 0.0

        self.transform.m41 = (startPoint.x + endPoint.x) / 2.0
        self.transform.m42 = (startPoint.y + endPoint.y) / 2.0
        self.transform.m43 = (startPoint.z + endPoint.z) / 2.0
        self.transform.m44 = 1.0
        return self
    }


func normalizeVector(_ iv: SCNVector3) -> SCNVector3 {
    let length = sqrt(iv.x * iv.x + iv.y * iv.y + iv.z * iv.z)
    if length == 0 {
        return SCNVector3(0.0, 0.0, 0.0)
    }

    return SCNVector3( iv.x / length, iv.y / length, iv.z / length)

}

我仍然不确定为什么会失败，当两个点的 x,z 坐标相同，但 y 坐标完全不同时。

如果有人能向我解释，我将非常高兴。

提前致谢。

Answer 1

看看你的代码，对于一些可以用更少的代码实现的东西来说，它看起来非常复杂。

此代码可以与 SCNBox 或 SCNCylinder 几何一起使用。

class MeasuringLineNode: SCNNode{

init(startingVector vectorA: GLKVector3, endingVector vectorB: GLKVector3) {
    super.init()

    //1. Create The Height Our Box Which Is The Distance Between Our 2 Vectors
    let height = CGFloat(GLKVector3Distance(vectorA, vectorB))

    //2. Set The Nodes Position At The Same Position As The Starting Vector
    self.position = SCNVector3(vectorA.x, vectorA.y, vectorA.z)

    //3. Create A Second Node Which Is Placed At The Ending Vectors Posirions
    let nodeVectorTwo = SCNNode()
    nodeVectorTwo.position = SCNVector3(vectorB.x, vectorB.y, vectorB.z)

    //4. Create An SCNNode For Alignment Purposes At 90 Degrees
    let nodeZAlign = SCNNode()
    nodeZAlign.eulerAngles.x = Float.pi/2

    //5. Create An SCNCyclinder Geometry To Act As Our Line
    let cylinder = SCNCylinder(radius: 0.001, height: height)
    let material = SCNMaterial()
    material.diffuse.contents = UIColor.white
    cylinder.materials = [material]

    /*
     If you want to use an SCNBox then use the following:

     let box = SCNBox(width: 0.001, height: height, length: 0.001, chamferRadius: 0)
     let material = SCNMaterial()
     material.diffuse.contents = UIColor.white
     box.materials = [material]

    */

    //6. Create The LineNode Centering On The Alignment Node
    let nodeLine = SCNNode(geometry: cylinder)
    nodeLine.position.y = Float(-height/2)
    nodeZAlign.addChildNode(nodeLine)

    self.addChildNode(nodeZAlign)

    //7. Force The Node To Look At Our End Vector
    self.constraints = [SCNLookAtConstraint(target: nodeVectorTwo)]
}

required init?(coder aDecoder: NSCoder) { fatalError("init(coder:) has not been implemented") }
}

假设您有 2 个 SCNNodes（在我的示例中，我将简单地称为 nodeA 和 nodeB），您可以像这样创建一个连接线：

//1. Convert The Nodes SCNVector3 to GLVector3
let nodeAVector3 = GLKVector3Make(nodeA.position.x, nodeA.position.y, nodeA.position.z)
let nodeBVector3 = GLKVector3Make(nodeB.position.x, nodeB.position.y, nodeB.position.z)

//2. Draw A Line Between The Nodes
let line = MeasuringLineNode(startingVector: nodeAVector3 , endingVector: nodeBVector3)
self.augmentedRealityView.scene.rootNode.addChildNode(line)

希望这对您有所帮助...

无法为某些情况创建圆柱体 - Arkit

Unable to create Cylinder for certain situations - Arkit

ios

swift

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