diff --git a/avlivebody-mac/Sources/AVLiveBody/SceneController.swift b/avlivebody-mac/Sources/AVLiveBody/SceneController.swift
new file mode 100644
index 0000000..571601d
--- /dev/null
+++ b/avlivebody-mac/Sources/AVLiveBody/SceneController.swift
@@ -0,0 +1,106 @@
+import Foundation
+import CoreVideo
+import RealityKit
+import simd
+import AVLiveWire
+
+/// Owns the single RealityKit scene: the video quad, the body root,
+/// and an orbital camera. The app calls `updateVideo/updateSkeleton/
+/// updateMesh` from the main queue.
+@MainActor
+final class SceneController {
+    let arView = ARView(frame: .zero)
+
+    private let cameraAnchor = AnchorEntity(world: .zero)
+    private let camera = PerspectiveCamera()
+    private let worldAnchor = AnchorEntity(world: .zero)
+
+    private(set) var videoQuad: VideoQuad?
+    private(set) var skeleton: SkeletonEntity?
+    private(set) var mesh: MeshEntity?
+
+    /// Orbital camera state.
+    private var orbitYaw: Float = 0
+    private var orbitPitch: Float = 0
+    private var orbitRadius: Float = 3.0
+
+    func setUp() {
+        arView.environment.background = .color(.black)
+        arView.scene.addAnchor(worldAnchor)
+
+        camera.camera.fieldOfViewInDegrees = 55
+        cameraAnchor.addChild(camera)
+        arView.scene.addAnchor(cameraAnchor)
+        applyCamera()
+
+        let q = VideoQuad()
+        worldAnchor.addChild(q.entity)
+        videoQuad = q
+
+        let s = SkeletonEntity()
+        worldAnchor.addChild(s.root)
+        skeleton = s
+
+        let m = MeshEntity()
+        worldAnchor.addChild(m.root)
+        mesh = m
+
+        installOrbitGestures()
+    }
+
+    func updateVideo(_ pixelBuffer: CVPixelBuffer) {
+        videoQuad?.update(pixelBuffer)
+    }
+
+    func updateSkeleton(_ skeletons: [Int: SkeletonPayload]) {
+        skeleton?.update(skeletons)
+    }
+
+    func updateMesh(_ persons: [MultiHMRPerson]) {
+        mesh?.update(persons)
+    }
+
+    // MARK: - Orbital camera
+
+    private func applyCamera() {
+        let cy = cos(orbitYaw), sy = sin(orbitYaw)
+        let cp = cos(orbitPitch), sp = sin(orbitPitch)
+        let pos = SIMD3<Float>(orbitRadius * cp * sy,
+                               orbitRadius * sp,
+                               orbitRadius * cp * cy)
+        cameraAnchor.transform.translation = pos
+        camera.look(at: .zero, from: pos, relativeTo: nil)
+    }
+
+    private func installOrbitGestures() {
+        let pan = NSPanGestureRecognizer(
+            target: OrbitTarget.shared, action: #selector(
+                OrbitTarget.handlePan(_:)))
+        OrbitTarget.shared.controller = self
+        arView.addGestureRecognizer(pan)
+    }
+
+    fileprivate func orbit(dx: Float, dy: Float) {
+        orbitYaw += dx * 0.01
+        orbitPitch = max(-1.4, min(1.4, orbitPitch + dy * 0.01))
+        applyCamera()
+    }
+}
+
+/// Bridges the AppKit pan gesture to `SceneController.orbit`.
+final class OrbitTarget: NSObject {
+    static let shared = OrbitTarget()
+    weak var controller: SceneController?
+    private var last: CGPoint = .zero
+
+    @objc func handlePan(_ g: NSPanGestureRecognizer) {
+        let p = g.translation(in: g.view)
+        if g.state == .began { last = p }
+        let dx = Float(p.x - last.x)
+        let dy = Float(p.y - last.y)
+        last = p
+        Task { @MainActor in
+            self.controller?.orbit(dx: dx, dy: -dy)
+        }
+    }
+}
diff --git a/avlivebody-mac/Sources/AVLiveBody/SceneView.swift b/avlivebody-mac/Sources/AVLiveBody/SceneView.swift
new file mode 100644
index 0000000..66aaf5c
--- /dev/null
+++ b/avlivebody-mac/Sources/AVLiveBody/SceneView.swift
@@ -0,0 +1,15 @@
+import RealityKit
+import SwiftUI
+
+/// SwiftUI bridge that hands the SceneController's ARView to the
+/// window and runs `setUp()` once.
+struct SceneView: NSViewRepresentable {
+    let controller: SceneController
+
+    func makeNSView(context: Context) -> ARView {
+        controller.setUp()
+        return controller.arView
+    }
+
+    func updateNSView(_ view: ARView, context: Context) {}
+}