name: axiom-ios-graphics description: Use when working with ANY GPU rendering, Metal, OpenGL migration, shaders, frame rate, or display performance. Covers Metal migration, shader conversion, variable refresh rate, ProMotion, render loops.

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