0
I’m using ARKit + SceneKit (Swift) with ARWorldTrackingConfiguration and detectionImages to place a 3D object (USDZ via SCNScene(named:)) when a reference image is detected. While the image is tracked, the object stays correctly aligned.
Goal: When the tracked image is no longer visible, I want the placed node to remain visible and fixed at its last known pose (no drifting) as I move the camera.
What works so far: Detect image → add node → track updates When the image disappears → keep showing the node at its last pose
Problem: After the image is no longer tracked, the node drifts as I move the device/camera. It looks like it’s still influenced by the (now unreliable) image anchor or accumulating small world-tracking errors.
Question: What’s the correct way in ARKit to “freeze” the node at its last known world transform once ARImageAnchor stops tracking, so it doesn’t drift?
Selecting any option will automatically load the page
Post
Replies
Boosts
Views
Created
We’re using the enterprise API for spatial barcode/QR code scanning in the Vision Pro app, but we often get invalid values for the barcode anchor from the API, leading to jittery barcode positions in the UI. The code we’re using is attached below.
import SwiftUI
import RealityKit
import ARKit
import Combine
struct ImmersiveView: View {
@State private var arkitSession = ARKitSession()
@State private var root = Entity()
@State private var fadeCompleteSubscriptions: Set = []
var body: some View {
RealityView { content in
content.add(root)
}
.task {
// Check if barcode detection is supported; otherwise handle this case.
guard BarcodeDetectionProvider.isSupported else { return }
// Specify the symbologies you want to detect.
let barcodeDetection = BarcodeDetectionProvider(symbologies: [.code128, .qr, .upce, .ean13, .ean8])
do {
try await arkitSession.requestAuthorization(for: [.worldSensing])
try await arkitSession.run([barcodeDetection])
print("Barcode scanning started")
for await update in barcodeDetection.anchorUpdates where update.event == .added {
let anchor = update.anchor
// Play an animation to indicate the system detected a barcode.
playAnimation(for: anchor)
// Use the anchor's decoded contents and symbology to take action.
print(
"""
Payload: \(anchor.payloadString ?? "")
Symbology: \(anchor.symbology)
""")
}
} catch {
// Handle the error.
print(error)
}
}
}
// Define this function in ImmersiveView.
func playAnimation(for anchor: BarcodeAnchor) {
guard let scene = root.scene else { return }
// Create a plane sized to match the barcode.
let extent = anchor.extent
let entity = ModelEntity(mesh: .generatePlane(width: extent.x, depth: extent.z), materials: [UnlitMaterial(color: .green)])
entity.components.set(OpacityComponent(opacity: 0))
// Position the plane over the barcode.
entity.transform = Transform(matrix: anchor.originFromAnchorTransform)
root.addChild(entity)
// Fade the plane in and out.
do {
let duration = 0.5
let fadeIn = try AnimationResource.generate(with: FromToByAnimation<Float>(
from: 0,
to: 1.0,
duration: duration,
isAdditive: true,
bindTarget: .opacity)
)
let fadeOut = try AnimationResource.generate(with: FromToByAnimation<Float>(
from: 1.0,
to: 0,
duration: duration,
isAdditive: true,
bindTarget: .opacity))
let fadeAnimation = try AnimationResource.sequence(with: [fadeIn, fadeOut])
_ = scene.subscribe(to: AnimationEvents.PlaybackCompleted.self, on: entity, { _ in
// Remove the plane after the animation completes.
entity.removeFromParent()
}).store(in: &fadeCompleteSubscriptions)
entity.playAnimation(fadeAnimation)
} catch {
print("Error")
}
}
}