Draft of Example 018 - Using handAnchors(at:) for predicted hand positions

Example018.swift

struct Example018: View {
    let arSession = ARKitSession()
    let handTrackingProvider = HandTrackingProvider()
    let leftCollection = Entity()
    let rightCollection = Entity()

    let tipJoints: [HandSkeleton.JointName] = [
        .thumbTip, .indexFingerTip, .middleFingerTip, .ringFingerTip, .littleFingerTip
    ]

    var body: some View {
        RealityView { content in
            content.add(leftCollection)
            content.add(rightCollection)

            if let scene = try? await Entity(named: "HandTrackingLabs", in: realityKitContentBundle) {
                content.add(scene)

                if let leftHandSphere = scene.findEntity(named: "StepSphereBlue") {
                    // Create clones of the left hand sphere for each joint
                    for jointName in tipJoints {
                        let sphere = leftHandSphere.clone(recursive: true)
                        sphere.name = jointName.description
                        leftCollection.addChild(sphere)
                    }
                    leftHandSphere.isEnabled = false
                }

                if let rightHandSphere = scene.findEntity(named: "StepSphereGreen") {
                    // Create clones of the right hand sphere for each joint
                    for jointName in tipJoints {
                        let sphere = rightHandSphere.clone(recursive: true)
                        sphere.name = jointName.description
                        rightCollection.addChild(sphere)
                    }
                    rightHandSphere.isEnabled = false
                }
            }
        }
        .persistentSystemOverlays(.hidden)

        .task { try! await arSession.run([handTrackingProvider]) }

        // Left Hand: Receive updates from the provider and process them over time
        .task {
            for await update in handTrackingProvider.anchorUpdates where update.anchor.chirality == .left {
                let handAnchor = update.anchor
                for jointName in tipJoints {
                    if let joint = handAnchor.handSkeleton?.joint(jointName),
                       let sphere = leftCollection.findEntity(named: jointName.description) {
                        let transform = handAnchor.originFromAnchorTransform
                        let jointTransform = joint.anchorFromJointTransform
                        sphere.setTransformMatrix(transform * jointTransform, relativeTo: nil)
                    }
                }
            }
        }
        // Right Hand: Using handAnchors(at:) for predicted hand positions
        .task {
            while true {
                let predictionTime = Date.now.timeIntervalSinceNow
                // let predictionTime = Date.now.timeIntervalSinceNow + (1.0/15.0)
                // let predictionTime = Date.now.timeIntervalSinceNow + (1.0/30.0)
                if let handAnchor = handTrackingProvider.handAnchors(at: predictionTime).rightHand {
                    for jointName in tipJoints {
                        if let joint = handAnchor.handSkeleton?.joint(jointName),
                           let sphere = rightCollection.findEntity(named: jointName.description) {
                            let transform = handAnchor.originFromAnchorTransform
                            let jointTransform = joint.anchorFromJointTransform
                            sphere.setTransformMatrix(transform * jointTransform, relativeTo: nil)
                        }
                    }
                }
                 try? await Task.sleep(for: .seconds(1/30))
                // try? await Task.sleep(for: .seconds(1/60))
//                try? await Task.sleep(for: .seconds(1/120))
            }
        }


    }
}