I am trying to use `projectPoint` to get the 2D information of the updated SCNNode in scenekit and save them.

Based on ignotusverum's suggestion, I am able to save the SCNNode in to a path in a button.

```
     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)
        }

```

---

Started saving via a start button:

```
    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()})
    }

```

---

Saved them via a stop button clicks:

```
@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")
    }
}

```

So far works fine with the points being saved. The problem is that in the saved data, I realized the data is only saving one frame of the x and y vertices. For example:

```
[(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)

```

The data is repeating with one frame rather than the period I want to save from the moment when I click start button to stop button.

**My question is how to save the updated SCNNode over time from the moment when I click start button to stop button?**

Thanks in advance!