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