Dispatch queue to animate SCNNode in ARKit - swift

Question

I'm facing an issue when trying to periodically animate my nodes on an ARSession. I'm fetching data from Internet every 5 seconds and then with that data I update this nodes (shrink or enlarge).
My code looks something like this:
Timer.scheduledTimer(withTimeInterval: 5, repeats: true) { timer in
fetchDataFromServer() {
let fetchedData = $0
DispatchQueue.main.async {
node1.update(fetchedData)
node2.update(fetchedData)
node3.update(fetchedData)
}
if stopCondition { timer.invalidate() }
}
}
Problem is that when calling the updates I'm seeing a glitch in which the camera seems to freeze for a fraction of second and I see the following message in the console: [Technique] World tracking performance is being affected by resource constraints [1]
Update happens correctly, but the UX is really clumpsy if every 5 seconds I get these "short freezes"
I've tried creating a concurrent queue too:
let animationQueue = DispatchQueue(label: "animationQueue", attributes: DispatchQueue.Attributes.concurrent)
and call animationQueue.async instead of main queue but problem persists.
I'd appreciate any suggestions.
EDIT: Each of the subnodes on it's update method looks like this
private func growingGeometryAnimation(newHeight height: Float) -> CAAnimation{
// Change height
let grow = CABasicAnimation(keyPath: "geometry.height")
grow.toValue = height
grow.fromValue = prevValue
// .... and the position
let move = CABasicAnimation(keyPath: "position.y")
let newPosition = getNewPosition(height: height)
move.toValue = newPosition.y + (yOffset ?? 0)
let growGroup = CAAnimationGroup()
growGroup.animations = [grow, move]
growGroup.duration = 0.5
growGroup.beginTime = CACurrentMediaTime()
growGroup.timingFunction = CAMediaTimingFunction(
name: kCAMediaTimingFunctionEaseInEaseOut)
growGroup.fillMode = kCAFillModeForwards
growGroup.isRemovedOnCompletion = false
growGroup.delegate = self
return growGroup
}
self.addAnimation(growingGeometryAnimation(newHeight: self.value), forKey: "bar_grow_animation")

Answer 1

To make any updates to the scene use SCNTransaction, it makes sure all of the changes are made on the appropriate thread.
Timer.scheduledTimer(withTimeInterval: 5, repeats: true) { timer in
fetchDataFromServer() {
let fetchedData = $0
SCNTransaction.begin()
node1.update(fetchedData)
node2.update(fetchedData)
node3.update(fetchedData)
SCNTransaction.commit()
if stopCondition { timer.invalidate() }
}
}