Quick start

We’ll build a screen that shows the camera, the live elbow angle and the reps. By the end you’ll have the three pieces every integration uses: pose source, session and events.

Create the pose source and the session

VisionPoseProvider reads the front camera and delivers one Pose per frame. MotionSession takes those poses for one exercise and one side of the body.

import KinesiaMotion
import KinesiaMotionVision

let camera = VisionPoseProvider(camera: .front)
let session = MotionSession(exercise: ExerciseLibrary.elbowFlexion, side: .right)

Ask for permission and start

if !VisionPoseProvider.isAuthorized {
    guard await VisionPoseProvider.requestAccess() else { return }
}
session.start(with: camera)

The camera turns on when the session starts reading poses and turns itself off when you call session.stop().

Draw from the snapshot

MotionSession is @Observable: SwiftUI redraws whenever session.snapshot changes.

Text(session.snapshot.value.map { "\(Int($0))°" } ?? "—")
Text("\(session.snapshot.repCount) reps")

React to events

Events are for things that happen once: a finished rep, a form correction.

for await event in session.events() {
    switch event {
    case .repCompleted(let rep): print("✓ \(Int(rep.peak))°")
    case .formFault(let fault):  print("Fix: \(fault)")
    default: break
    }
}

The full example

import SwiftUI
import AVFoundation
import KinesiaMotion
import KinesiaMotionVision

struct ElbowView: View {
    @State private var camera = VisionPoseProvider(camera: .front)
    @State private var session = MotionSession(exercise: ExerciseLibrary.elbowFlexion, side: .right)
    @State private var message = "Stand sideways and show your whole arm"

    var body: some View {
        ZStack(alignment: .bottom) {
            CameraPreview(session: camera.captureSession)
                .ignoresSafeArea()

            VStack(spacing: 8) {
                Text(session.snapshot.value.map { "\(Int($0))°" } ?? "—")
                    .font(.system(size: 64, weight: .bold, design: .rounded))
                Text("\(session.snapshot.repCount) reps · best \(Int(session.snapshot.best))°")
                Text(message).font(.callout)
            }
            .padding()
            .background(.ultraThinMaterial, in: .rect(cornerRadius: 20))
            .padding()
        }
        .task {
            if !VisionPoseProvider.isAuthorized {
                guard await VisionPoseProvider.requestAccess() else { return }
            }
            session.start(with: camera)

            for await event in session.events() {
                switch event {
                case .repCompleted(let rep):
                    message = "Nice! \(Int(rep.peak))°"
                case .repRejected:
                    message = "That one doesn't count: watch your form"
                case .formFault(.keepUpperArmStill):
                    message = "Keep your upper arm by your side"
                case .visibilityChanged(let visibility) where !visibility.isVisible:
                    message = "I can't see your whole arm"
                default:
                    break
                }
            }
        }
        .onDisappear { session.stop() }
    }
}

/// The camera image behind everything.
struct CameraPreview: UIViewRepresentable {
    let session: AVCaptureSession

    func makeUIView(context: Context) -> PreviewView {
        let view = PreviewView()
        view.previewLayer.session = session
        view.previewLayer.videoGravity = .resizeAspectFill
        return view
    }

    func updateUIView(_ uiView: PreviewView, context: Context) {}

    final class PreviewView: UIView {
        override class var layerClass: AnyClass { AVCaptureVideoPreviewLayer.self }
        var previewLayer: AVCaptureVideoPreviewLayer { layer as! AVCaptureVideoPreviewLayer }
    }
}

Next steps

Understand how the engine works inside.
Add a baseline measurement to know where the patient starts.
Use measurement quality to guide placement in front of the camera.