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
- •Translation layer vs native rewrite? → metal-migration
- •Porting / converting code to Metal? → metal-migration
- •API reference / shader conversion tables? → metal-migration-ref
- •MTKView / render pipeline setup? → metal-migration-ref
- •Something broken after porting (black screen, wrong colors)? → metal-migration-diag
- •Stuck at 60fps on ProMotion device? → display-performance
- •CADisplayLink / variable refresh rate? → display-performance
- •Frame rate not as expected? → display-performance
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. |
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