iOS Graphics Router

You MUST use this skill for ANY GPU rendering, graphics programming, 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

Routing Logic

Metal Migration

Strategy decisions → /skill axiom-metal-migration - Translation layer vs native rewrite decision - Project assessment and migration planning - Anti-patterns and common mistakes - Pressure scenarios for deadline resistance

API reference & conversion → /skill axiom-metal-migration-ref - 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 → /skill axiom-metal-migration-diag - 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 → /skill axiom-display-performance - App stuck at 60fps on ProMotion (120Hz) device - MTKView or CADisplayLink configuration - Variable refresh rate optimization - System caps (Low Power Mode, Limit Frame Rate, Adaptive Power) - Frame budget math (8.33ms for 120Hz) - Measuring actual vs reported frame rate

Decision Tree

User asks about GPU/graphics/Metal/display
  ├─ "Should I use translation layer or native?" → metal-migration
  ├─ "How do I migrate/port/convert?" → metal-migration
  ├─ "Show me the API/code/example" → metal-migration-ref
  ├─ "How do I set up MTKView?" → metal-migration-ref
  ├─ "Something's broken/wrong/slow" → metal-migration-diag
  ├─ "Stuck at 60fps on ProMotion" → display-performance
  ├─ "CADisplayLink setup/configuration" → display-performance
  ├─ "Variable refresh rate issues" → display-performance
  └─ "Frame rate not what I expect" → display-performance

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

Example Invocations

User: "Should I use MetalANGLE or rewrite in native Metal?" → Invoke: /skill axiom-metal-migration

User: "I'm porting projectM from OpenGL ES to iOS" → Invoke: /skill axiom-metal-migration

User: "How do I convert this GLSL shader to Metal?" → Invoke: /skill axiom-metal-migration-ref

User: "Setting up MTKView for the first time" → Invoke: /skill axiom-metal-migration-ref

User: "My ported app shows a black screen" → Invoke: /skill axiom-metal-migration-diag

User: "Performance is worse after porting to Metal" → Invoke: /skill axiom-metal-migration-diag

User: "My app is stuck at 60fps on iPhone Pro" → Invoke: /skill axiom-display-performance

User: "How do I configure CADisplayLink for 120Hz?" → Invoke: /skill axiom-display-performance

User: "ProMotion not working in my Metal app" → Invoke: /skill axiom-display-performance