ios - Swift:使用scenekit 中的projectPoint 随时间获取并保存更新的SCNNode

Question

我正在尝试使用 projectPoint在scenekit中获取更新后的SCNNode的二维信息并保存。
根据 ignotusverum 的建议，我可以将 SCNNode 保存到按钮中的路径中。

     var lastPosition: CGPoint?
     func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
            guard anchor == currentFaceAnchor,
                let contentNode = selectedContentController.contentNode,
                contentNode.parent == node
                else { return }
            for (index, vertex) in vertices.enumerated() {
            let vertex = sceneView.projectPoint(node.convertPosition(SCNVector3(vertex), to: nil))
            let xVertex = CGFloat(vertex.x)
            let yVertex = CGFloat(vertex.y)
            Position = CGPoint(x: xVertex, y: yVertex)
           }
            selectedContentController.session = sceneView?.session
            selectedContentController.sceneView = sceneView
            selectedContentController.renderer(renderer, didUpdate: contentNode, for: anchor)
        }

通过开始按钮开始保存:

    private var fpsTimer = Timer()
    private var currentCaptureFrame = 0
    @IBAction private func startPressed() {
        currentCaptureFrame = 0 //inital capture frame
        fpsTimer = Timer.scheduledTimer(withTimeInterval: 1/fps, repeats: true, block: {(timer) -> Void in self.recordData()})
    }

通过单击停止按钮保存它们:

@IBAction private func stopPressed() {
    do {
        fpsTimer.invalidate() //turn off the timer
        let capturedData = captureData.map{$0.stringRepresentation}.joined(separator:"\(lastPosition)>")
        let dir: URL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).last! as URL
        let url = dir.appendingPathComponent("testing.txt")
        try capturedData.appendLineToURL(fileURL: url as URL)
    }
    catch {
        print("Could not write to file")
    }
}

到目前为止，保存点的效果很好。问题是在保存的数据中，我意识到数据只保存了 x 和 y 顶点的一帧。例如:

[(411.0618591308594, 534.4215087890625), (410.7286071777344, 544.9381713867188), (411.5425720214844, 522.1063232421875), (412.0340881347656, 512.1854248046875),... 

[(411.0618591308594, 534.4215087890625), (410.7286071777344, 544.9381713867188), (411.5425720214844, 522.1063232421875), (412.0340881347656, 512.1854248046875)

数据以一帧重复，而不是从我单击开始按钮到停止按钮的那一刻起保存的时间段。
我的问题是如何从我单击开始按钮到停止按钮的那一刻起随时间保存更新的 SCNNode？
提前致谢!

Answer 1

如果我正确理解您的问题，您希望在每次更新顶点位置时保存它们，跟踪所有以前的更新以及最近的更新。为此，您只需将新的顶点位置数组附加到具有保存数据的全局数组中。

 var savedPositions = [CGPoint]()
 var beginSaving = false

 func renderer(_ renderer: SCNSceneRenderer, didUpdate node: SCNNode, for anchor: ARAnchor) {
        guard anchor == currentFaceAnchor,
            let contentNode = selectedContentController.contentNode,
            contentNode.parent == node
            else { return }
        for vertex in vertices {
            let projectedPoint = sceneView.projectPoint(node.convertPosition(SCNVector3(vertex), to: nil))
            if beginSaving {
               savedPositions.append(CGPoint(x: projectedPoint.x, y: projectedPoint.y))
            }
        }
        selectedContentController.session = sceneView?.session
        selectedContentController.sceneView = sceneView
        selectedContentController.renderer(renderer, didUpdate: contentNode, for: anchor)
}

@IBAction private func startPressed() {
    beginSaving = true
}

@IBAction private func stopPressed() {
    beginSaving = false
    ....//do whatever with your array of saved positions
}