visionOS Object Tracking Enhancements

import ARKit
import RealityKit
import UIKit

class ObjectTrackingViewController: UIViewController, ARSessionDelegate {
    var arView: ARView!
    var session: ARSession!

    override func viewDidLoad() {
        super.viewDidLoad()
        arView = ARView(frame: view.bounds)
        arView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        view.addSubview(arView)

        session = arView.session
        session.delegate = self

        guard let referenceObjectURL = Bundle.main.url(
            forResource: "flashlight",
            withExtension: "referenceobject"
        ) else {
            print("Reference object not found in bundle")
            return
        }

        ARReferenceObject.referenceObjects(
            inGroupNamed: nil,
            bundle: Bundle.main
        )

        let referenceObject = try! ARReferenceObject(archiveURL: referenceObjectURL)

        let configuration = ARWorldTrackingConfiguration()
        // Use trackingObjects for high frame rate tracking of moving/handheld objects
        configuration.trackingObjects = [referenceObject]
        // Use detectionObjects for mostly stationary objects
        // configuration.detectionObjects = [referenceObject]

        session.run(configuration, options: [.resetTracking, .removeExistingAnchors])
    }

    // MARK: - ARSessionDelegate

    func session(_ session: ARSession, didAdd anchors: [ARAnchor]) {
        for anchor in anchors.compactMap({ $0 as? ARObjectAnchor }) {
            print("Object detected: \(anchor.referenceObject.name ?? "unknown")")
            attachVirtualContent(to: anchor, in: arView)
        }
    }

    func session(_ session: ARSession, didUpdate anchors: [ARAnchor]) {
        for anchor in anchors.compactMap({ $0 as? ARObjectAnchor }) {
            // iOS 27: obtain pose in metric space without display corrections
            // Use .none for measurement tasks; .rendered for visual alignment
            let metricTransform = anchor.transform(for: .none)
            let renderedTransform = anchor.transform(for: .rendered)

            let position = SIMD3<Float>(
                metricTransform.columns.3.x,
                metricTransform.columns.3.y,
                metricTransform.columns.3.z
            )
            print("Metric position (meters): \(position)")
        }
    }

    func session(_ session: ARSession, didRemove anchors: [ARAnchor]) {
        for anchor in anchors.compactMap({ $0 as? ARObjectAnchor }) {
            print("Object removed: \(anchor.referenceObject.name ?? "unknown")")
            // Remove any entities tied to this anchor
        }
    }

    private func attachVirtualContent(to anchor: ARObjectAnchor, in arView: ARView) {
        let anchorEntity = AnchorEntity(anchor: anchor)
        let mesh = MeshResource.generateBox(size: 0.02)
        let material = SimpleMaterial(color: .systemBlue, isMetallic: true)
        let modelEntity = ModelEntity(mesh: mesh, materials: [material])
        anchorEntity.addChild(modelEntity)
        arView.scene.addAnchor(anchorEntity)
    }
}