Culling occluded geometry using the visibility result buffer

At a glance

Project structure

Source bundle/
├── Application/
│   ├── main.m
│   ├── AAPLAppDelegate.h
│   ├── AAPLAppDelegate.m
│   ├── AAPLViewController.h
│   ├── AAPLViewController.m
│   ├── WindowSceneDelegate.h
│   ├── WindowSceneDelegate.m
│   └── iOS/
│       └── Base.lproj/
│           └── Main.storyboard
└── Renderer/
    ├── AAPLRenderer.h
    ├── AAPLRenderer.m
    ├── AAPLShaders.metal
    └── AAPLShaderTypes.h

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: C/Objective-C header, Metal, Objective-C.
• The verified tree contains 9 project/configuration file(s) and 6 source declaration(s).

Overall architecture

flowchart LR
    N1["main"]
    N2["AAPLViewController"]
    N3["AAPLRenderer"]
    N4["metal_stdlib APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

Application/main.m:12 — architecture anchor

#if defined(TARGET_MACOS)
int main(int argc, const char * argv[])
{
    @autoreleasepool {
        return NSApplicationMain(argc, argv);
    }
}
#endif

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 Metal.

Ownership and state

classDiagram
    AAPLAppDelegate o-- PlatformWindow : window
    WindowSceneDelegate o-- UIWindow : window
    AAPLRenderer o-- size_t : numVisibleFragments
    AAPLRenderer o-- size_t : numSpheresDrawn

Ownership evidence

Application/AAPLAppDelegate.h:27 — stored dependency or nearest verified ownership anchor

#if defined(TARGET_MACOS)
@property (strong, nonatomic) PlatformWindow *window;
#endif

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.

Concurrency, scheduling, and thread safety

Evidence limit: actor isolation, async/await, or Task creation does not by itself prove background-thread execution; Sendable conformance alone does not prove thread-safe mutation.

No source-visible execution, scheduling, or synchronization boundary was found in the indexed source.

@MainActor/MainActor.run, DispatchQueue.main, and RunLoop.main are reported as distinct isolation, queue, and event-loop mechanisms. A plain Task is kept separate from Task.detached; neither is labeled as a background thread.

State propagation, frameworks, and dependencies

Evidence limit: an import proves a source-level compilation dependency at the cited line; it does not prove runtime use, architectural adoption, or whether a Swift package is a direct application dependency.

receive(on:) describes downstream delivery scheduling, while subscribe(on:) describes upstream subscription/request/cancel scheduling. An import Combine alone establishes neither behavior nor a Store, reducer, Redux, or other application architecture.

Class and protocol design

Application/AAPLAppDelegate.h:24 — representative type boundary

@interface AAPLAppDelegate : PlatformAppDelegate

#if defined(TARGET_MACOS)
@property (strong, nonatomic) PlatformWindow *window;
#endif

@end

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

Access control

Reference code

Application/AAPLAppDelegate.h:27 — representative boundary

#if defined(TARGET_MACOS)
@property (strong, nonatomic) PlatformWindow *window;
#endif

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

Main application flow

sequenceDiagram
    participant AAPLViewController
    participant _renderer
    participant NSString
    participant _modeDisplay
    participant _numDisplay
    AAPLViewController->>_renderer: drawInMTKView()
    AAPLViewController->>NSString: initWithFormat()
    AAPLViewController->>NSString: initWithFormat()
    AAPLViewController->>_modeDisplay: setStringValue()
    AAPLViewController->>_numDisplay: setStringValue()
    AAPLViewController->>_modeDisplay: setText()
    AAPLViewController->>_numDisplay: setText()

Reference code

Application/AAPLViewController.m:121 — drawInMTKView()

- (void) drawInMTKView:(nonnull MTKView*) view
{
#if defined(TARGET_TVOS)
    // The sample animates the position variable for lack of a slider control.
    _renderer.position = sin(CACurrentMediaTime() / 5.0);
#endif
    [_renderer drawInMTKView:view];

    // Set the label and value depending on the mode of the app.
    NSString* label = @"";
    NSString* value = @"";
    if(_renderer.visibilityTestingMode == AAPLFragmentCountingMode)
    {
        label = @"Fragment count:";
        value = [[NSString alloc] initWithFormat:@"%lu", _renderer.numVisibleFragments];
    }
    else if(_renderer.visibilityTestingMode == AAPLOcclusionCullingMode)
    {
        label = @"Spheres drawn:";
        value = [[NSString alloc] initWithFormat:@"%lu / %u", _renderer.numSpheresDrawn, AAPLNumObjectsXYZ];
    }

#if defined(TARGET_MACOS)
    [_modeDisplay setStringValue:label];
    [_numDisplay setStringValue:value];
#elif defined(TARGET_IOS) || defined(TARGET_TVOS)
    [_modeDisplay setText:label];
    [_numDisplay setText:value];
#endif
}

Naming conventions

• Types: Controller: AAPLViewController; Delegate: AAPLAppDelegate, WindowSceneDelegate; Renderer: AAPLRenderer.
• Protocols: no local protocol declaration in the scanned source.
• Methods: application, viewDidLoad, optionChanged, modeChanged, toggleMode, drawInMTKView, mtkView, scene.
• Files: Application/AAPLAppDelegate.h, Application/AAPLAppDelegate.m, Application/AAPLViewController.h, Application/AAPLViewController.m, Application/WindowSceneDelegate.h, Application/WindowSceneDelegate.m.

Architecture takeaways

• main is the main source-visible entry or composition anchor for this sample.
• Framework work reaches metal_stdlib, simd 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