I'm placing sphere at finger tip and updating its position as hand move.
Finger joint tracking functions correctly, but I’ve observed noticeable latency in hand tracking updates whenever a UITextView becomes active. This lag happens intermittently during app usage, lasting about 5–10 seconds, after which the latency disappears and the sphere starts following the finger joints immediately.
When I open the immersive space for the first time, the profiler shows a large performance spike upto 328%. After that, it stabilizes and runs smoothly.
Note: I don’t observe any lag when CPU usage spikes to 300% (upon immersive view load)
yet the lag still occurs even when CPU usage remains below 100%.
I’m using the following code for hand tracking:
private func processHandTrackingUpdates() async {
for await update in handTracking.anchorUpdates {
let handAnchor = update.anchor
if handAnchor.isTracked {
switch handAnchor.chirality {
case .left:
leftHandAnchor = handAnchor
updateHandJoints(for: handAnchor, with: leftHandJointEntities)
case .right:
rightHandAnchor = handAnchor
updateHandJoints(for: handAnchor, with: rightHandJointEntities)
}
} else {
switch handAnchor.chirality {
case .left:
leftHandAnchor = nil
hideAllJoints(in: leftHandJointEntities)
case .right:
rightHandAnchor = nil
hideAllJoints(in: rightHandJointEntities)
}
}
await MainActor.run {
handTrackingData.processNewHandAnchors(
leftHand: self.leftHandAnchor,
rightHand: self.rightHandAnchor
)
}
}
}
And here’s the function I’m using to update the joint positions:
private func updateHandJoints(
for handAnchor: HandAnchor,
with jointEntities: [HandSkeleton.JointName: Entity]
) {
guard handAnchor.isTracked else {
hideAllJoints(in: jointEntities)
return
}
// Check if the little finger tip and intermediate base are both tracked.
if let tipJoint = handAnchor.handSkeleton?.joint(.littleFingerTip),
let intermediateBaseJoint = handAnchor.handSkeleton?.joint(.littleFingerIntermediateTip),
tipJoint.isTracked,
intermediateBaseJoint.isTracked,
let pinkySphere = jointEntities[.littleFingerTip] {
// Convert joint transforms to world space.
let tipTransform = handAnchor.originFromAnchorTransform * tipJoint.anchorFromJointTransform
let intermediateBaseTransform = handAnchor.originFromAnchorTransform * intermediateBaseJoint.anchorFromJointTransform
// Extract positions from the transforms.
let tipPosition = SIMD3<Float>(tipTransform.columns.3.x,
tipTransform.columns.3.y,
tipTransform.columns.3.z)
let intermediateBasePosition = SIMD3<Float>(intermediateBaseTransform.columns.3.x,
intermediateBaseTransform.columns.3.y,
intermediateBaseTransform.columns.3.z)
// Calculate the midpoint.
let midpointPosition = (tipPosition + intermediateBasePosition) / 2.0
// Position the sphere at the midpoint and make it visible.
pinkySphere.isEnabled = true
pinkySphere.transform.translation = midpointPosition
} else {
// If either joint is not tracked, hide the sphere.
jointEntities[.littleFingerTip]?.isEnabled = false
}
// Update the positions of all other hand joint spheres.
for (jointName, entity) in jointEntities {
if jointName == .littleFingerTip {
// Already handled the pinky above.
continue
}
guard let joint = handAnchor.handSkeleton?.joint(jointName),
joint.isTracked else {
entity.isEnabled = false
continue
}
entity.isEnabled = true
let jointTransform = handAnchor.originFromAnchorTransform * joint.anchorFromJointTransform
entity.transform.translation = SIMD3<Float>(jointTransform.columns.3.x,
jointTransform.columns.3.y,
jointTransform.columns.3.z)
}
}
I’ve attached both a profiler trace and a video recording from Vision Pro that clearly demonstrate the issue.
Profiler: https://drive.google.com/file/d/1fDWyGj_fgxud2ngkGH_IVmuH_kO-z0XZ
Vision Pro Recordings:
https://drive.google.com/file/d/17qo3U9ivwYBsbaSm26fjaOokkJApbkz-
https://drive.google.com/file/d/1LxTxgudMvWDhOqKVuhc3QaHfY_1x8iA0
Has anyone else experienced this behavior? My thought is that there might be some background calculations happening at the OS level causing this latency. Any guidance would be greatly appreciated.
Thanks!
