SceneKit - 在3D對象上繪圖

Question

我創建了在3d對象上繪制的示例應用程序，輸出圖形不平滑（如圖所示）。 我花了將近一天的時間來弄清楚仍然無法解決的問題。 可能是什么問題？

我正在創建如下的自定義繪圖幾何

//I am creating self.drawingNode touches begin and adding to the rootnode
//points are nothing but 2d points from touches

func createGeometryForPoints(points:[CGPoint]) -> SCNGeometry {

    var all_3d_points:[SCNVector3] = []

    for point in points {

        let result = self.get3dPoint(point)

        if result.1 == true {
            all_3d_points.append(result.0)
        } else {
            print("INVALID POINT")
        }
    }

    var indices: [Int32] = []
    var index:Int32 = 0

    var previousIndex:Int32 = -1

    for _ in all_3d_points {

        if(previousIndex != -1) {

            indices.append(previousIndex)
        }
        indices.append(index)
        index = index + 1
        previousIndex = index
    }

    if indices.count > 0 {
        indices.removeLast();
    }

    let indexData = NSData(bytes: indices, length: sizeof(Int32) * indices.count)

    let source = SCNGeometrySource.init(vertices: all_3d_points, count: all_3d_points.count)
    let element = SCNGeometryElement.init(data: indexData, primitiveType: .Line, primitiveCount: indices.count/2, bytesPerIndex: sizeof(Int32))

    let line = SCNGeometry(sources: [source], elements: [element])
    line.materials.first?.diffuse.contents = UIColor.redColor()
    line.materials.first?.doubleSided = true

    return line
}

func get3dPoint(point:CGPoint) -> (SCNVector3,Bool) {

    var canAdd = false
    let scnView = self.view as! SCNView
    var unprojectedStartPoint = SCNVector3.init(x:Float(point.x), y:Float(point.y), z:0)

    let hitResults = scnView.hitTest(point, options: nil)
    if hitResults.count > 0 {

        let result: AnyObject! = hitResults[0]
        if hitResults.count > 1 {
            print("SOME PROBLEM")
        }
        unprojectedStartPoint = result.localCoordinates
        unprojectedStartPoint = result.node.convertPosition(unprojectedStartPoint, toNode: self.drawingNode!)

        canAdd = true
    }

    return (unprojectedStartPoint,canAdd)
}

編輯

我正在考慮找到偏移以及相機方向或正常，因為我是scenekit的新手，我沒有得到如何將這個偏移添加到繪圖節點，在這個方向尋找幫助

 func createMarkup() -> Void { let drawingNode = SCNNode() drawingNode.renderingOrder = 1000 self.parentNode!.addChildNode(drawingNode) let geometry = self.createGeometryForPoints(allPoints,node: drawingNode) drawingNode.geometry = geometry drawingNode.geometry?.materials.first?.doubleSided = true } 

編輯：2

通過在命中測試的正常情況下添加次要偏移來解決問題

let offsetToAvoidFlickering: Float = 0.05
unprojectedStartPoint = unprojectedStartPoint + result.localNormal.normalized() * offsetToAvoidFlickering

Answer 1

我懷疑你有深度精度問題; 看起來你的部分線被剪裁了，因為它們是球體的相交部分。 嘗試繪制禁用深度測試的線。

Answer 2

SceneKit狀態的Union演示示例代碼顯示了類似的效果，您可以在圓環上繪制。 它的功能更強大，因為你可以畫任何東西（不僅僅是線，但是從質地等飛濺），並更有效，因為它不依賴於創造新的幾何體。