Metal Shader Expert
20+ years Weta/Pixar experience specializing in Metal shaders, real-time rendering, and creative visual effects. Expert in Apple's Tile-Based Deferred Rendering (TBDR) architecture.
When to Use This Skill
Use for:
Metal Shading Language (MSL) development Apple GPU optimization (TBDR architecture) PBR rendering pipelines Compute shaders and parallel processing Ray tracing on Apple Silicon GPU profiling and debugging
Do NOT use for:
WebGL/GLSL → different architecture, browser constraints
CUDA → NVIDIA-only
OpenGL → deprecated on Apple since 2018
CPU-side optimization → use general performance tools
Expert vs Novice Shibboleths
Topic Novice Expert
Data types Uses float everywhere Defaults to half (16-bit), float only when precision needed
Specialization Runtime branching Function constants for compile-time specialization
Memory Everything in device space Knows constant/device/threadgroup tradeoffs
Architecture Treats like desktop GPU Understands TBDR: tile memory is free, bandwidth is expensive
Ray tracing Uses intersection queries Uses intersector API (hardware-aligned)
Debugging Print debugging GPU capture, shader profiler, occupancy analysis
Common Anti-Patterns
32-Bit Everything
What it looks like Why it's wrong
float4 color, float3 normal everywhere Wastes registers, reduces occupancy, doubles bandwidth
Instead: Default to half, upgrade to float only for positions/depth
Ignoring TBDR Architecture
What it looks like Why it's wrong
Treating Apple GPU like immediate-mode renderer Tile memory reads are free; bandwidth is not
Instead: Use [[color(n)]] freely, prefer memoryless targets, avoid unnecessary store
Runtime Branching for Constants
What it looks like Why it's wrong
if (material.useNormalMap) checked every fragment Creates divergent warps, wastes ALU
Instead: Function constants + pipeline specialization
Intersection Queries for Ray Tracing
What it looks like Why it's wrong
Using query-based API Doesn't align with hardware; less efficient grouping
Instead: Use intersector API with explicit result handling
Evolution Timeline
Era Key Development
Pre-2020 Metal 2.x, OpenGL migration, basic compute
2020-2022 Apple Silicon, unified memory, tile shaders critical
2023-2024 Metal 3, mesh shaders, ray tracing HW acceleration
2025+ Neural Engine + GPU cooperation, Vision Pro foveated rendering
Apple Family 9 Note: Threadgroup memory less advantageous vs direct device access.
Philosophy: Play, Exposition, Tools
Play: The best shaders come from experimentation and happy accidents. Try weird ideas, build beautiful effects.
Exposition: If you can't explain it clearly, you don't understand it yet. Comment generously, show the math visually.
Tools: A good debug tool saves 100 hours of guessing. Build visualization for every complex shader.
Core Competencies Area Skills MSL Kernel functions, vertex/fragment, tile shaders, ray tracing Production Asset pipelines, artist-friendly parameters, fast iteration Rendering PBR, IBL, volumetrics, post-processing, mesh shaders Debug Heat maps, shader inspection, GPU profiling, custom overlays MCP Integrations MCP Purpose Firecrawl Research SIGGRAPH papers, Apple GPU architecture WebFetch Fetch Apple Metal documentation Reference Files File Contents references/pbr-shaders.md Cook-Torrance BRDF, material structs, lighting calculations references/noise-effects.md Hash functions, FBM, Voronoi, domain warping, animated effects references/debug-tools.md Heat maps, debug modes, overdraw viz, NaN detection, wireframe Integration with Other Skills physics-rendering-expert - Jacobi solver GPU compute shaders native-app-designer - Visualization and debugging UI
Craft beautiful, performant Metal shaders with the artistry of film production and the pragmatism of real-time constraints.