Particles Speed Up When Recording A Video Using ARVideoKit - swift

Question

We have an ARKit & SceneKit app that records videos using ARVideoKit pod (link). Inside our scene we have a fire particle. Fire is playing at a slow speed. However, when you start recording a video the fire particle speeds up. I can't figure out why the fire particle is speeding up. Please see the video (here) to see the issue.
Here's a sample project which you can use to test the issue: Project
I would appreciate if anyone can explain why this is happening.
Edit 1: Below is my ViewController Code
import UIKit
import ARKit
import SceneKit
import ARVideoKit
class ViewController: UIViewController, ARSCNViewDelegate {
#IBOutlet var sceneView: ARSCNView!
#IBOutlet weak var photoButton: UIButton!
#IBOutlet weak var videoButton: UIButton!
#IBOutlet weak var takeVideoButtonPressedLabel: UILabel!
// ARVideoKit Variables
var recorder : RecordAR?
var takenImage: UIImage?
var takenVideoAtURL : URL?
let recordingQueue = DispatchQueue(label: "recordingThread", attributes: .concurrent)
var arTrackingConfig = ARWorldTrackingConfiguration()
override func viewDidLoad() {
super.viewDidLoad()
sceneView.delegate = self
sceneView.scene = SCNScene(named: "art.scnassets/fire.scn")!
self.resetTracking()
}
func resetTracking() {
arTrackingConfig = ARWorldTrackingConfiguration()
arTrackingConfig.isLightEstimationEnabled = true
sceneView.session.run(arTrackingConfig, options: [.resetTracking,
.removeExistingAnchors])
}
}
// MARK: - ARVideoKit Implementation
extension ViewController {
#IBAction func takePhoto(_ sender: UIButton) {
// Do Nothing
}
#IBAction func takeVideo(_ sender: UIButton) {
setupCamera()
startRecording()
}
func setupCamera() {
recorder = RecordAR(ARSceneKit: sceneView)
recorder?.prepare(arTrackingConfig)
}
func startRecording() {
takeVideoButtonPressedLabel.isHidden = false
recordingQueue.async {
self.recorder?.record(forDuration: 5) { path in
self.takenVideoAtURL = path
DispatchQueue.main.async {
self.takeVideoButtonPressedLabel.isHidden = true
}
}
}
}
}
Edit 2: Added sample project for testing.

Answer 1

While getting the image from SCNRenderer using snapshot method pass 0 as time , this way force rendering will not happen and animations will be smoother. In your case particles will not speed up