Culling occluded geometry using the visibility result buffer

At a glance

Project structure

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

Structure observations

• The entry/composition boundary and renderer or operation boundary are separate in the source; AAPLRenderer is the principal feature coordinator.
• GPU-specific logic stays in Metal shader files; shared headers bridge host/shader layouts where present.
• The tree above is intentionally pruned to composition, resource, and shader files.

Overall architecture

flowchart LR
    N1["AAPLViewController"]
    N2["AAPLRenderer"]
    N3["visibility-query buffer management"]
    N4["occlusion-tested draw calls"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

Renderer/AAPLRenderer.m:568 — per-object visibility query encoding

    for (size_t i = 0; i < AAPLNumObjectsXYZ; ++i)
    {
        [_renderEncoder setVisibilityResultMode:MTLVisibilityResultModeBoolean
                                         offset:i * sizeof(uint64_t)];
        [self renderMeshWithIndex:(uint32_t)i];
    }

Interpretation

This is the dominant control/data path: platform code composes AAPLRenderer; that object controls visibility-query buffer management; GPU-visible work ends in occlusion-tested draw calls. The arrows summarize responsibility transfer, not a claim that every node directly calls the next.

Ownership and state

classDiagram
    AAPLViewController *-- AAPLRenderer : _renderer

Ownership evidence

Application/AAPLViewController.m:57 — AAPLViewController creates and stores _renderer

    _renderer = [[AAPLRenderer alloc] initWithMetalKitView:_view];
    NSAssert(_renderer, @"Renderer failed initialization");

    [_renderer drawableSizeWillChange:_view.bounds.size];

    // The view controller needs to update state for the renderer, so use this class's `MTKView` methods first.
    _view.delegate = self;

Class and protocol design

Framework delegate conformance is a callback seam; the source does not justify calling the whole app protocol-oriented.

Access control

This sample does not use Swift private, fileprivate, or public for its native boundary. Objective-C/Objective-C++ use header versus implementation placement, C++ uses access specifiers/linkage, Python uses module conventions, and Metal entry points cross a compiled-library boundary; these are not Swift access levels.

Logic ownership and placement

Shader boundary reference

Renderer/AAPLShaders.metal:37 — representative GPU entry/helper

vertex RasterizerData vertexShader(const device vector_float4* positions [[buffer(AAPLBufferIndexPositions)]],
                                   constant AAPLFrameData& frameData [[buffer(AAPLBufferIndexFrameData)]],
                                   constant MeshIndexData& meshIndex [[buffer(AAPLBufferIndexMeshIndex)]],
                                   uint vertexID [[vertex_id]])
{
    // ...
}

Design patterns

Naming conventions

• Role suffixes make ownership visible: AAPLViewController, AAPLRenderer, AAPLAppDelegate, WindowSceneDelegate.
• Method names describe setup or encoding actions: application, viewDidLoad, optionChanged, modeChanged, toggleMode, drawInMTKView, mtkView.
• Shader entry points use stage/operation names: vertexShader, fragmentShader.
• AAPL is a sample namespace prefix, not a recommendation for production module naming; retain semantic suffixes such as Renderer, Manager, Scene, or Adapter.

Architecture takeaways

• Keep AAPLViewController focused on composition; AAPLRenderer is the owner of visibility-query buffer management.
• Treat occlusion-tested draw calls as a separate execution/compilation boundary with explicit resource and data-layout contracts.
• The verified ownership edge is AAPLViewController → _renderer; broader exclusive ownership is not inferred.
• Access-control rationale follows concrete language boundaries rather than translating every header or shader symbol into Swift terms.

Source map

• Official Apple documentation