Capturing Body Motion in 3D

At a glance

Project structure

Source bundle/
├── BodyDetection/
│   ├── AppDelegate.swift
│   ├── ViewController.swift
│   ├── Base.lproj/
│   │   ├── LaunchScreen.storyboard
│   │   └── Main.storyboard
│   └── Info.plist
├── BodyDetection.xcodeproj/
│   ├── .xcodesamplecode.plist
│   └── project.pbxproj
└── Configuration/
    └── SampleCode.xcconfig

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: Swift.
• The verified tree contains 6 project/configuration file(s) and 2 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["ViewController"]
    N3["ARKit APIs"]
    N1 --> N2
    N2 --> N3

Reference code

BodyDetection/AppDelegate.swift:10 — architecture anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
}

Interpretation

The arrows summarize the source-visible entry, role-named types or folders, and framework direction; when nodes come from structural folders, the sequence is a high-level interpretation rather than proof that every adjacent node calls the next. Ownership is claimed only where the next section cites a stored property or assignment. The diagram is intentionally limited to the dominant path into ARKit.

Ownership and state

classDiagram
    AppDelegate o-- UIWindow : window
    ViewController o-- ARView : arView
    ViewController o-- BodyTrackedEntity : character
    ViewController *-- SIMD3 : characterOffset

Ownership evidence

BodyDetection/AppDelegate.swift:13 — stored dependency or nearest verified ownership anchor

    var window: UIWindow?

    func application(_ application: UIApplication,
                     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?)
        -> Bool {
        return true
    }

Composition arrows indicate a source-visible construction expression or locally owned value state; aggregation means the owner stores or receives a dependency without proving exclusive lifetime ownership.

Class and protocol design

BodyDetection/AppDelegate.swift:11 — representative type boundary

class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
}

No local protocol conformance is claimed as protocol-oriented design; external framework conformances are listed only as dependencies.

Access control

Reference code

BodyDetection/AppDelegate.swift:11 — representative boundary

class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
}

Swift declarations without a modifier are internal; explicit private, fileprivate, private(set), public, or open entries above are interpreted by language semantics. Objective-C/C samples instead rely on header and implementation boundaries, which are not equivalent to Swift lexical privacy.

Logic ownership and placement

Design patterns

Naming conventions

• Types: Controller: ViewController; Delegate: AppDelegate.
• Protocols: no local protocol declaration in the scanned source.
• Methods: application, applicationWillResignActive, applicationDidEnterBackground, applicationWillEnterForeground, applicationDidBecomeActive, applicationWillTerminate, viewDidAppear, session.
• Files: BodyDetection/AppDelegate.swift, BodyDetection/ViewController.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches UIKit, ARKit, RealityKit through a deliberately small high-level chain; the detailed API graph remains inside the cited implementation files.
• Stored-property evidence identifies lifecycle collaboration; it does not by itself prove exclusive object ownership.
• Access-control conclusions separate verified language visibility from the likely design rationale.
• The source does not justify labeling the design protocol-oriented.

Source map

• Official Apple documentation