ios - 像测量应用程序一样在scenekit中绘制虚线圆柱体？

Question

我已经按照这个问题尝试制作破折号气缸

final class LineNode: SCNNode {

    convenience init(positionA: SCNVector3, positionB: SCNVector3) {
        self.init()

        let vector = SCNVector3(positionA.x - positionB.x, positionA.y - positionB.y, positionA.z - positionB.z)
        let distance = vector.length
        let midPosition = (positionA + positionB) / 2

        let lineGeometry = SCNCylinder()
        lineGeometry.radius = PileDrawer3D.lineWidth
        lineGeometry.height = CGFloat(distance)
        lineGeometry.radialSegmentCount = 5

        lineGeometry.firstMaterial?.diffuse.contents = dashedImage
        lineGeometry.firstMaterial?.diffuse.contentsTransform = SCNMatrix4MakeScale(distance * 10, Float(lineGeometry.radius * 10), 1)
        lineGeometry.firstMaterial?.diffuse.wrapS = .repeat
        lineGeometry.firstMaterial?.diffuse.wrapT = .repeat
        lineGeometry.firstMaterial?.isDoubleSided = true
        lineGeometry.firstMaterial?.multiply.contents = UIColor.green
        lineGeometry.firstMaterial?.lightingModel = .constant

        let rotation = SCNMatrix4MakeRotation(.pi / 2, 0, 0, 1)
        lineGeometry.firstMaterial?.diffuse.contentsTransform = SCNMatrix4Mult(rotation, lineGeometry.firstMaterial!.diffuse.contentsTransform)

        geometry = lineGeometry
        position = midPosition
        eulerAngles = SCNVector3.lineEulerAngles(vector: vector)

        name = className
    }

    lazy var dashedImage: UIImage = {

        let size = CGSize(width: 10, height: 3)
        UIGraphicsBeginImageContextWithOptions(size, true, 0)
        UIColor.white.setFill()
        UIRectFill(CGRect(x: 0, y: 0, width: 7, height: size.height))
        let img = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return img!
    }()

}

但是，管道没有虚线。

我不确定我在这里缺少什么，请帮忙。

更新T：

事实证明，清晰的颜色（在图像中）被渲染为黑色，在 SCNView 中不透明。不过，不知道为什么绿色会这样变暗。

Answer 1

Line & DashLine 的另一种方法

final class LineNode: SCNNode {

    var color: UIColor? {
        set { geometry?.firstMaterial?.diffuse.contents = newValue }
        get { geometry?.firstMaterial?.diffuse.contents as? UIColor }
    }

    convenience init(positionA: SCNVector3, positionB: SCNVector3, dash: CGFloat = 0, in scene: SCNScene? = nil) {
        self.init()
        let indices: [Int32] = [0, 1]
        let source = SCNGeometrySource(vertices: [positionA, positionB])
        let element = SCNGeometryElement(indices: indices, primitiveType: .line)
        geometry = SCNGeometry(sources: [source], elements: [element])
        geometry?.firstMaterial?.diffuse.contents = UIColor.green
        geometry?.firstMaterial?.lightingModel = .constant

        return
    }
}

final class DashLineNode: SCNNode {
    convenience init(positionA: SCNVector3, positionB: SCNVector3) {
        self.init()
        let vector = (positionB - positionA)
        let length = floor(vector.length / 1)
        let segment = vector / length

        let indices:[Int32] = Array(0..<Int32(length))
        var vertices = [positionA]
        for _ in indices {
            vertices.append(vertices.last! + segment)
        }
        let source = SCNGeometrySource(vertices: vertices)
        let element = SCNGeometryElement(indices: indices, primitiveType: .line)

        geometry = SCNGeometry(sources: [source], elements: [element])
        geometry?.firstMaterial?.lightingModel = .constant
    }
}