axiom-graphics

name	axiom-graphics
description	Use when working with ANY GPU rendering, Metal, OpenGL migration, shaders, 3D content, RealityKit, AR, USD/USDZ files, or display performance. Covers Metal migration, shader conversion, RealityKit ECS, RealityView, USDKit, ProMotion.
license	MIT

Graphics

You MUST use this skill for ANY GPU rendering, graphics programming, 3D content display, or display performance work.

When to Use

Use this router when:

• Porting OpenGL/OpenGL ES code to Metal
• Porting DirectX code to Metal
• Converting GLSL/HLSL shaders to Metal Shading Language
• Setting up MTKView or CAMetalLayer
• Rendering breaks or blurs when the window resizes or moves between screens
• Debugging GPU rendering issues (black screen, wrong colors, crashes)
• Evaluating translation layers (MetalANGLE, MoltenVK)
• Optimizing GPU performance or fixing thermal throttling
• App stuck at 60fps on ProMotion device
• Configuring CADisplayLink or render loops
• Variable refresh rate display issues
• Displaying 3D content in a non-game SwiftUI app
• Building AR experiences with RealityKit
• Using RealityView or Model3D in SwiftUI
• Spatial computing or visionOS 3D content
• Reading, editing, or exporting USD/USDZ files in Swift (USDKit)
• Adding ML to a render pipeline (MetalFX denoising, Metal tensors, neural rendering)
• Profiling long game sessions (metalperftrace, look-back traces)

Routing Logic

Metal Migration

Strategy decisions → See skills/metal-migration.md

• Translation layer vs native rewrite decision
• Project assessment and migration planning
• Anti-patterns and common mistakes
• Pressure scenarios for deadline resistance

API reference & conversion → See skills/metal-migration-ref.md

• GLSL → MSL shader conversion tables
• HLSL → MSL shader conversion tables
• GL/D3D API → Metal API equivalents
• MTKView setup, render pipelines, compute shaders
• Complete WWDC code examples

Diagnostics → See skills/metal-migration-diag.md

• Black screen after porting
• Shader compilation errors
• Wrong colors or coordinate systems
• Performance regressions
• Time-cost analysis per diagnostic path

Rendering Surfaces Under Window Resizing

Any rendering surface in a resizable window → See skills/resizable-rendering.md

• MTKView drawableSizeWillChange (projection + render-target reallocation, live-resize throttling)
• CAMetalLayer manual drawableSize/contentsScale ownership
• Per-surface adaptation table: video layers, maps, charts, Canvas, web views, PDF, SpriteKit/SceneKit
• displayScale-keyed cache invalidation when a scene moves between screens (Mirroring, external display)

Display Performance

Frame rate & render loops → See skills/display-performance.md

• App stuck at 60fps on ProMotion (120Hz) device
• MTKView or CADisplayLink configuration
• Variable refresh rate optimization
• System caps (Low Power Mode, Limit Frame Rate, Thermal, Adaptive Power)
• Frame budget math (8.33ms for 120Hz)
• Measuring actual vs reported frame rate

RealityKit (Non-Game 3D Content)

For 3D content in non-game SwiftUI apps, AR experiences, and spatial computing, use the RealityKit skills. For game-specific RealityKit patterns, use the axiom-games router instead.

Architecture, ECS, and best practices → See skills/realitykit.md

• Entity-Component-System architecture
• SwiftUI integration: RealityView, Model3D, attachments
• AR on iOS: AnchorEntity types, SpatialTrackingSession
• Materials, physics, interaction
• Performance optimization

API reference → See skills/realitykit-ref.md

• Complete component catalog
• RealityView and Model3D API
• Material system (PBR, Unlit, Occlusion, Custom)
• RealityRenderer (Metal integration)

Troubleshooting → See skills/realitykit-diag.md

• Entity not visible, anchor not tracking
• Gesture not responding, performance issues
• Material problems, physics issues

HDR Tone Mapping & Color

HDR drawing and color metadata → See skills/hdr-color-ref.md

• HDR images washed out, clipped, or dark when drawn into a CGContext
• Choosing a tone-mapping method (CGContentToneMappingInfo vs CGToneMapping)
• Headroom Adaptive Gain Curve metadata on ICC profiles (OS27)
• Persisting CGColor / CGColorSpace (Codable in OS27)

USD Authoring (USDKit) OS27

USD file work in Swift → See skills/usdkit.md

• Open, traverse, edit USD stages and prims
• References and composition
• Accessibility metadata for 3D assets
• USDZ export with mesh/texture compression
• Rendering a USD stage in RealityKit (USDStageComponent)

Decision Tree

1. Translation layer vs native rewrite? → metal-migration
2. Porting / converting code to Metal? → metal-migration
3. API reference / shader conversion tables? → metal-migration-ref
4. MTKView / render pipeline setup? → metal-migration-ref
5. Something broken after porting (black screen, wrong colors)? → metal-migration-diag
6. Stuck at 60fps on ProMotion device? → display-performance
7. CADisplayLink / variable refresh rate? → display-performance
8. Frame rate not as expected? → display-performance
9. Display a 3D model in SwiftUI? → realitykit
10. Build an AR experience? → realitykit
11. RealityView or Model3D setup? → realitykit-ref
12. 3D content not visible or not tracking? → realitykit-diag
13. Custom Metal rendering of RealityKit content? → realitykit-ref (RealityRenderer)
14. Pathfinding, LOD, soft shadows, splats, reverb meshes? → realitykit-ref (Part 10)
15. Read/edit/export a USD or USDZ file in Swift? → usdkit
16. ML in the render pipeline (denoising, Metal tensors)? → metal-migration-ref (Part 6)
17. Frame drops in long play sessions? → display-performance (Part 12)
18. HDR image looks washed out / clipped when drawn? → hdr-color-ref
19. Choosing a tone-mapping method, or reading HAGC metadata? → hdr-color-ref
20. Rendering stretches, blurs, or letterboxes when the window resizes or moves screens? → resizable-rendering
21. Building a 3D game? → Use axiom-games router instead

Anti-Rationalization

Thought	Reality
"I'll just translate the shaders line by line"	GLSL→MSL has type, coordinate, and precision differences. metal-migration-ref has conversion tables.
"MetalANGLE will handle everything"	Translation layers have significant limitations for production. metal-migration evaluates the trade-offs.
"It's just a black screen, probably a simple bug"	Black screen has 6 distinct causes. metal-migration-diag diagnoses in 5 min vs 30+ min.
"My app runs at 60fps, that's fine"	ProMotion devices support 120Hz. display-performance configures the correct frame rate.
"I'll just use SceneKit for the 3D model"	SceneKit is soft-deprecated. RealityView and Model3D are the modern path. skills/realitykit.md covers SwiftUI integration.
"I don't need ECS for one 3D model"	Model3D shows one model with zero ECS. RealityView scales to complex scenes. skills/realitykit.md shows both paths.
"I'll parse the USD file myself / bundle OpenUSD"	USDKit is system-provided USD on the 27 releases. skills/usdkit.md covers stages, editing, and compressed export.
"I'll write my own pathfinding over the scene graph"	RealityKit 27 ships navigation meshes with costs and off-mesh connections. skills/realitykit-ref.md Part 10.
"The frame drop only happens after an hour of play, can't trace that"	The 27 releases record Metal metrics continuously — collect after the fact with metalperftrace. skills/display-performance.md Part 12.
"I'll size my render target from the screen bounds"	Windows resize continuously at 27 and scenes move between screens with different scales. Size from the drawable/view + trait scale — skills/resizable-rendering.md.
"I'll use CGContentToneMappingInfo — it's the modern Swift enum"	It cannot express Headroom Adaptive Gain Curve; only the C-imported CGToneMapping can. Newer spelling, narrower capability. skills/hdr-color-ref.md Part 1.

Critical Patterns

metal-migration:

• Translation layer (MetalANGLE) for quick demos
• Native Metal rewrite for production
• State management differences (GL stateful → Metal explicit)
• Coordinate system gotchas (Y-flip, NDC differences)

metal-migration-ref:

• Complete shader type mappings
• API equivalent tables
• MTKView vs CAMetalLayer decision
• Render pipeline setup patterns

metal-migration-diag:

• GPU Frame Capture workflow (2-5 min vs 30+ min guessing)
• Shader debugger for variable inspection
• Metal validation layer for API misuse
• Performance regression diagnosis

display-performance:

• MTKView defaults to 60fps (must set preferredFramesPerSecond = 120)
• CADisplayLink preferredFrameRateRange for explicit rate control
• System caps: Low Power Mode, Limit Frame Rate, Thermal, Adaptive Power (iOS 26)
• 8.33ms frame budget for 120Hz
• UIScreen.maximumFramesPerSecond lies; CADisplayLink tells truth

realitykit (non-game 3D):

• RealityView make/update closure pattern
• Model3D for simple model display
• AR anchoring with AnchorEntity
• Material selection (SimpleMaterial, PBR, Occlusion)

realitykit-ref (API):

• RealityRenderer for custom Metal rendering of RealityKit content
• Complete material property reference
• RealityView gesture integration
• RealityKit 27 additions: navigation mesh, LOD, soft shadows, Gaussian splats (visionOS), reverb meshes (Part 10), cloth simulation (ClothBodyComponent), ComputeGraph framework

usdkit (USD authoring, 27 releases):

• USDStage open/traverse/edit, references and composition
• Accessibility metadata schema for 3D assets
• Compressed USDZ export (AOM meshes + AVIF textures)
• USDStageComponent / USDPlayer RealityKit bridge

Example Invocations

User: "My MTKView content stretches when the iPad window resizes" → See skills/resizable-rendering.md

User: "My cached thumbnails look blurry in iPhone Mirroring" → See skills/resizable-rendering.md

User: "Should I use MetalANGLE or rewrite in native Metal?" → See skills/metal-migration.md

User: "I'm porting projectM from OpenGL ES to iOS" → See skills/metal-migration.md

User: "How do I convert this GLSL shader to Metal?" → See skills/metal-migration-ref.md

User: "Setting up MTKView for the first time" → See skills/metal-migration-ref.md

User: "My ported app shows a black screen" → See skills/metal-migration-diag.md

User: "Performance is worse after porting to Metal" → See skills/metal-migration-diag.md

User: "My app is stuck at 60fps on iPhone Pro" → See skills/display-performance.md

User: "How do I configure CADisplayLink for 120Hz?" → See skills/display-performance.md

User: "ProMotion not working in my Metal app" → See skills/display-performance.md

User: "How do I show a 3D model in my SwiftUI app?" → See skills/realitykit.md

User: "I need to display a USDZ model" → See skills/realitykit.md

User: "How do I set up RealityView?" → See skills/realitykit-ref.md

User: "My 3D model isn't showing in RealityView" → See skills/realitykit-diag.md

User: "How do I use RealityRenderer with Metal?" → See skills/realitykit-ref.md

User: "I need AR in my app" → See skills/realitykit.md

User: "How do I read and edit a USD file in Swift?" → See skills/usdkit.md

User: "How do I shrink my USDZ assets for delivery?" → See skills/usdkit.md

User: "How do I add pathfinding to my RealityKit scene?" → See skills/realitykit-ref.md (Part 10)

User: "My game's frame rate drops after an hour of play" → See skills/display-performance.md (Part 12)

User: "How do I run a neural network inside my Metal shader?" → See skills/metal-migration-ref.md (Part 6)

User: "My HDR photo looks washed out when I draw it into a CGContext" → See skills/hdr-color-ref.md

User: "How do I check whether an image's ICC profile carries a gain curve?" → See skills/hdr-color-ref.md