How to capture AR frames as UIImages at 30FPS in ARKit.

For a full tutorial on how to capture video — click here.

In any case, here’s how to do it:

Step One: Add these variables to your system

var isRecording:Bool = false
var snapshotArray:[[String:Any]] = [[String:Any]]()
var lastTime:TimeInterval = 0

Step Two: Add the functionality

In your func renderer(_ renderer: SCNSceneRenderer, updateAtTime time: TimeInterval) call the following function — and yes, it does have to be coded this way, else your system freezes or crashes.

public func didUpdateAtTime(time: TimeInterval) {
if self.isRecording {
if self.lastTime == 0 || (self.lastTime + 1/31) < time {
DispatchQueue.main.async { [weak self] () -> Void in
guard self != nil else { return }
self!.lastTime = time;
let snapshot:UIImage = self!.sceneView.snapshot()
let scale = CMTimeScale(NSEC_PER_SEC)
self!.snapshotArray.append([
"image":snapshot,
"time": CMTime(value: CMTimeValue((self?.sceneView.session.currentFrame!.timestamp)! * Double(scale)), timescale: scale)
]);
}
}

You now have a functionality that can be triggered by a button which creates an array with snapshots as UIImages and timestamps in seconds.

Step Three: Camera Button Functionality

Start Recording:

func startRecording() {
self.lastTime = 0;
self.isRecording = true;
}

End Recording:

func stopRecording() {
self.isRecording = false;
print("ARRAY COUNT : \(self.snapshotArray.count) ")
self.snapshotArray.removeAll();
Filemanager.default.clearTmpFiles();
}

That it for now folks.

O