charleswiltgen/axiom-graphics

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
• 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

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

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

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? → axiom-realitykit
10. Build an AR experience? → axiom-realitykit
11. RealityView or Model3D setup? → axiom-realitykit-ref
12. 3D content not visible or not tracking? → axiom-realitykit-diag
13. Custom Metal rendering of RealityKit content? → axiom-realitykit-ref (RealityRenderer)
14. 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. axiom-realitykit covers SwiftUI integration. | | "I don't need ECS for one 3D model" | Model3D shows one model with zero ECS. RealityView scales to complex scenes. axiom-realitykit shows both paths. |

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

axiom-realitykit (non-game 3D):

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

axiom-realitykit-ref (API):

• RealityRenderer for custom Metal rendering of RealityKit content
• Complete material property reference
• RealityView gesture integration

Example Invocations

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