Skip to main content
Shader Dev – Agent Skill by MiniMax • Craftwork
36 ShaderToy-style GLSL techniques, including signed distance fields, ray marching, fluids, noise and post-processing, with a routing table.
$ npx skills add https://craftwork.design/skills/shader-dev -a claude-code -y
SKILL.md Shader Craft
A unified skill covering 36 GLSL shader techniques (ShaderToy-compatible) for real-time visual effects.
Invocation
/shader-dev <request>
$ARGUMENTS contains the user's request (e.g. "create a raymarched SDF scene with soft shadows").
Skill Structure
shader-dev/
├── SKILL.md # Core skill (this file)
├── techniques/ # Implementation guides (read per routing table)
│ ├── ray-marching.md # Sphere tracing with SDF
│ ├── sdf-3d.md # 3D signed distance functions
│ ├── lighting-model.md # PBR, Phong, toon shading
│ ├── procedural-noise.md # Perlin, Simplex, FBM
│ └── ... # 34 more technique files
└── reference/ # Detailed guides (read as needed)
├── ray-marching.md # Math derivations & advanced patterns
├── sdf-3d.md # Extended SDF theory
├── lighting-model.md # Lighting math deep-dive
├── procedural-noise.md # Noise function theory
└── ... # 34 more reference files
How to Use
Read the Technique Routing Table below to identify which technique(s) match the user's request
Read the relevant file(s) from techniques/ — each file contains core principles, implementation steps, and complete code templates
If you need deeper understanding (math derivations, advanced patterns), follow the reference link at the bottom of each technique file to reference/
Apply the WebGL2 Adaptation Rules below when generating standalone HTML pages
Technique Routing Table User wants to create... Primary technique Combine with 3D objects / scenes from math ray-marching + sdf-3d lighting-model, shadow-techniques Complex 3D shapes (booleans, blends) csg-boolean-operations sdf-3d, ray-marching Infinite repeating patterns in 3D domain-repetition sdf-3d, ray-marching Organic / warped shapes domain-warping procedural-noise Fluid / smoke / ink effects fluid-simulation multipass-buffer Particle effects (fire, sparks, snow) particle-system procedural-noise, color-palette Physically-based simulations simulation-physics multipass-buffer Game of Life / reaction-diffusion cellular-automata multipass-buffer, color-palette Ocean / water surface water-ocean atmospheric-scattering, lighting-model Terrain / landscape terrain-rendering atmospheric-scattering, procedural-noise Clouds / fog / volumetric fire volumetric-rendering procedural-noise, atmospheric-scattering Sky / sunset / atmosphere atmospheric-scattering volumetric-rendering Realistic lighting (PBR, Phong) lighting-model shadow-techniques, ambient-occlusion Shadows (soft / hard) shadow-techniques lighting-model Ambient occlusion ambient-occlusion lighting-model, normal-estimation Path tracing / global illumination path-tracing-gi analytic-ray-tracing, multipass-buffer Precise ray-geometry intersections analytic-ray-tracing lighting-model Voxel worlds (Minecraft-style) voxel-rendering lighting-model, shadow-techniques Noise / FBM textures procedural-noise domain-warping Tiled 2D patterns procedural-2d-pattern polar-uv-manipulation Voronoi / cell patterns voronoi-cellular-noise color-palette Fractals (Mandelbrot, Julia, 3D) fractal-rendering color-palette, polar-uv-manipulation Color grading / palettes color-palette — Bloom / tone mapping / glitch post-processing multipass-buffer Multi-pass ping-pong buffers multipass-buffer — Texture / sampling techniques texture-sampling — Camera / matrix transforms matrix-transform — Surface normals normal-estimation — Polar coords / kaleidoscope polar-uv-manipulation procedural-2d-pattern 2D shapes / UI from SDF sdf-2d color-palette Procedural audio / music sound-synthesis — SDF tricks / optimization sdf-tricks sdf-3d, ray-marching Anti-aliased rendering anti-aliasing sdf-2d, post-processing Depth of field / motion blur / lens effects camera-effects post-processing, multipass-buffer Advanced texture mapping / no-tile textures texture-mapping-advanced terrain-rendering, texture-sampling WebGL2 shader errors / debugging webgl-pitfalls —
Technique Index
Geometry & SDF
sdf-2d — 2D signed distance functions for shapes, UI, anti-aliased renderingsdf-3d — 3D signed distance functions for real-time implicit surface modelingcsg-boolean-operations — Constructive solid geometry: union, subtraction, intersection with smooth blendingdomain-repetition — Infinite space repetition, folding, and limited tilingdomain-warping — Distort domains with noise for organic, flowing shapessdf-tricks — SDF optimization, bounding volumes, binary search refinement, hollowing, layered edges, debug visualization
Ray Casting & Lighting
ray-marching — Sphere tracing with SDF for 3D scene renderinganalytic-ray-tracing — Closed-form ray-primitive intersections (sphere, plane, box, torus)path-tracing-gi — Monte Carlo path tracing for photorealistic global illuminationlighting-model — Phong, Blinn-Phong, PBR (Cook-Torrance), and toon shadingshadow-techniques — Hard shadows, soft shadows (penumbra estimation), cascade shadowsambient-occlusion — SDF-based AO, screen-space AO approximationnormal-estimation — Finite-difference normals, tetrahedron technique
Simulation & Physics
fluid-simulation — Navier-Stokes fluid solver with advection, diffusion, pressure projectionsimulation-physics — GPU-based physics: springs, cloth, N-body gravity, collisionparticle-system — Stateless and stateful particle systems (fire, rain, sparks, galaxies)cellular-automata — Game of Life, reaction-diffusion (Turing patterns), sand simulation
Natural Phenomena
water-ocean — Gerstner waves, FFT ocean, caustics, underwater fogterrain-rendering — Heightfield ray marching, FBM terrain, erosionatmospheric-scattering — Rayleigh/Mie scattering, god rays, SSS approximationvolumetric-rendering — Volume ray marching for clouds, fog, fire, explosions
Procedural Generation
procedural-noise — Value noise, Perlin, Simplex, Worley, FBM, ridged noiseprocedural-2d-pattern — Brick, hexagon, truchet, Islamic geometric patternsvoronoi-cellular-noise — Voronoi diagrams, Worley noise, cracked earth, crystalfractal-rendering — Mandelbrot, Julia sets, 3D fractals (Mandelbox, Mandelbulb)color-palette — Cosine palettes, HSL/HSV/Oklab, dynamic color mapping
Post-Processing & Infrastructure
post-processing — Bloom, tone mapping (ACES, Reinhard), vignette, chromatic aberration, glitchmultipass-buffer — Ping-pong FBO setup, state persistence across framestexture-sampling — Bilinear, bicubic, mipmap, procedural texture lookupmatrix-transform — Camera look-at, projection, rotation, orbit controlspolar-uv-manipulation — Polar/log-polar coordinates, kaleidoscope, spiral mappinganti-aliasing — SSAA, SDF analytical AA, temporal anti-aliasing (TAA), FXAA post-processcamera-effects — Depth of field (thin lens), motion blur, lens distortion, film grain, vignettetexture-mapping-advanced — Biplanar mapping, texture repetition avoidance, ray differential filtering
Audio
sound-synthesis — Procedural audio in GLSL: oscillators, envelopes, filters, FM synthesis
Debugging & Validation
webgl-pitfalls — Common WebGL2/GLSL errors: fragCoord, main() wrapper, function order, macro limitations, uniform null
WebGL2 Adaptation Rules All technique files use ShaderToy GLSL style. When generating standalone HTML pages, apply these adaptations:
Shader Version & Output
Use canvas.getContext("webgl2")
Shader first line: #version 300 es, fragment shader adds precision highp float;
Fragment shader must declare: out vec4 fragColor;
Vertex shader: attribute → in, varying → out
Fragment shader: varying → in, gl_FragColor → fragColor, texture2D() → texture()
Fragment Coordinate
Use gl_FragCoord.xy instead of fragCoord (WebGL2 does not have fragCoord built-in) // WRONG
vec2 uv = (2.0 * fragCoord - iResolution.xy) / iResolution.y;
// CORRECT
vec2 uv = (2.0 * gl_FragCoord.xy - iResolution.xy) / iResolution.y;
main() Wrapper for ShaderToy Templates
ShaderToy uses void mainImage(out vec4 fragColor, in vec2 fragCoord)
WebGL2 requires standard void main() entry point — always wrap mainImage:
void mainImage(out vec4 fragColor, in vec2 fragCoord) {
// shader code...
fragColor = vec4(col, 1.0);
}
void main() {
mainImage(fragColor, gl_FragCoord.xy);
}
Function Declaration Order
GLSL requires functions to be declared before use — either declare before use or reorder:
// WRONG — getAtmosphere() calls getSunDirection() before it's defined
vec3 getAtmosphere(vec3 dir) { return getSunDirection(); } // Error!
vec3 getSunDirection() { return normalize(vec3(1.0)); }
// CORRECT — define callee first
vec3 getSunDirection() { return normalize(vec3(1.0)); }
vec3 getAtmosphere(vec3 dir) { return getSunDirection(); } // Works
Macro Limitations
#define cannot use function calls — use const instead: // WRONG
#define SUN_DIR normalize(vec3(0.8, 0.4, -0.6))
// CORRECT
const vec3 SUN_DIR = vec3(0.756, 0.378, -0.567); // Pre-computed normalized value
When extracting shader source from <script> tags, ensure #version is the first character — use .trim():
const fs = document.getElementById('fs').text.trim();
Common Pitfalls
Unused uniforms : Compiler may optimize away unused uniforms, causing gl.getUniformLocation() to return null — always use uniforms in a way the compiler cannot optimize outLoop indices : Use runtime constants in loops, not #define macros in some ES versionsTerrain functions : Functions like terrainM(vec2) need XZ components — use terrainM(pos.xz + offset) not terrainM(pos + offset)
HTML Page Setup When generating a standalone HTML page:
Canvas fills the entire viewport, auto-resizes on window resize
Page background black, no scrollbars: body { margin: 0; overflow: hidden; background: #000; }
Implement ShaderToy-compatible uniforms: iTime, iResolution, iMouse, iFrame
For multi-pass effects (Buffer A/B), use WebGL2 framebuffer + ping-pong (see multipass-buffer technique)
Common Pitfalls
JS Variable Declaration Order (TDZ — causes white screen crash) let/const variables must be declared at the top of the <script> block, before any function that references them:
// 1. State variables FIRST
let frameCount = 0;
let startTime = Date.now();
// 2. Canvas/GL init, shader compile, FBO creation
const canvas = document.getElementById('canvas');
const gl = canvas.getContext('webgl2');
// ...
// 3. Functions and event bindings LAST
function resize() { /* can now safely reference frameCount */ }
function render() { /* ... */ }
window.addEventListener('resize', resize);
Reason: let/const have a Temporal Dead Zone — referencing them before declaration throws ReferenceError, causing a white screen.
GLSL Compilation Errors (self-check after writing shaders)
Function signature mismatch : Call must exactly match definition in parameter count and types. If defined as float fbm(vec3 p), cannot call fbm(uv) with a vec2Reserved words as variable names : Do not use: patch, cast, sample, filter, input, output, common, partition, activeStrict type matching : vec3 x = 1.0 is illegal — use vec3 x = vec3(1.0); cannot use .z to access a vec2No ternary on structs : ESSL does not allow ternary operator on struct types — use if/else instead
Deployment environments may use headless software rendering with limited GPU power. Stay within these limits:
Ray marching main loop: ≤ 128 steps
Volume sampling / lighting inner loops: ≤ 32 steps
FBM octaves: ≤ 6 layers
Total nested loop iterations per pixel: ≤ 1000 (exceeding this freezes the browser)
Quick Recipes Common effect combinations — complete rendering pipelines assembled from technique modules.
Photorealistic SDF Scene
Geometry : sdf-3d (extended primitives) + csg-boolean-operations (cubic/quartic smin)Rendering : ray-marching + normal-estimation (tetrahedron method)Lighting : lighting-model (outdoor three-light model) + shadow-techniques (improved soft shadow) + ambient-occlusionAtmosphere : atmospheric-scattering (height-based fog with sun tint)Post : post-processing (ACES tone mapping) + anti-aliasing (2x SSAA) + camera-effects (vignette)
Geometry : sdf-3d (extended primitives + deformation operators: twist, bend) + csg-boolean (gradient-aware smin for material blending)Detail : procedural-noise (FBM with derivatives) + domain-warpingSurface : lighting-model (subsurface scattering approximation via half-Lambert)
Procedural Landscape
Terrain : terrain-rendering + procedural-noise (erosion FBM with derivatives)Texturing : texture-mapping-advanced (biplanar mapping + no-tile)Sky : atmospheric-scattering (Rayleigh/Mie + height fog)Water : water-ocean (Gerstner waves) + lighting-model (Fresnel reflections)
Stylized 2D Art
Shapes : sdf-2d (extended library) + sdf-tricks (layered edges, hollowing)Color : color-palette (cosine palettes) + polar-uv-manipulation (kaleidoscope)Polish : anti-aliasing (SDF analytical AA) + post-processing (bloom, chromatic aberration)
Shader Debugging Techniques Visual debugging methods — temporarily replace your output to diagnose issues.
What to check Code What to look for Surface normals col = nor * 0.5 + 0.5;Smooth gradients = correct normals; banding = epsilon too large Ray march step count col = vec3(float(steps) / float(MAX_STEPS));Red hotspots = performance bottleneck; uniform = wasted iterations Depth / distance col = vec3(t / MAX_DIST);Verify correct hit distances UV coordinates col = vec3(uv, 0.0);Check coordinate mapping SDF distance field col = (d > 0.0 ? vec3(0.9,0.6,0.3) : vec3(0.4,0.7,0.85)) * (0.8 + 0.2*cos(150.0*d));Visualize SDF bands and zero-crossing Checker pattern (UV) col = vec3(mod(floor(uv.x*10.)+floor(uv.y*10.), 2.0));Verify UV distortion, seams Lighting only col = vec3(shadow); or col = vec3(ao);Isolate shadow/AO contributions Material ID col = palette(matId / maxMatId);Verify material assignment
CloudAI-X
3D & shaders
19 KB
