shader

Write, explain, adapt, and debug practical shader code for GLSL, WebGL, Three.js ShaderMaterial, React Three Fiber, postprocess-style full-screen effects, and ShaderToy-style fragment shaders. Use when the user wants to create an effect shader, port a shader between runtimes, fix black screens or compile errors, wire uniforms like time or resolution, troubleshoot UV, normal, or color-space mistakes, or turn a visual idea into a runnable vertex/fragment pair. Also use when pairing shader output with OpenClaw canvas demos. NOT for full rendering-engine architecture, advanced offline rendering theory, or GPU-vendor-specific optimization claims that have not been verified in the target runtime.

Use this skill to turn shader requests into runnable code and fast debugging steps.

Default target: browser-friendly GLSL. If the runtime is unclear, narrow it before writing code:

• ShaderToy fragment-only
• raw WebGL / GLSL ES
• Three.js ShaderMaterial
• React Three Fiber
• postprocess-style full-screen pass

Workflow

1. Lock the runtime and effect shape

Resolve these first:

• runtime
• fragment-only vs vertex + fragment
• screen effect vs material effect vs postprocess pass
• required inputs: uTime, uResolution, UVs, normals, textures, mouse

If the request is vague, start with the smallest visible version of the effect.

2. Build from a visible baseline

• Start with a constant color or UV gradient.
• Add one moving term at a time.
• Reintroduce uniforms, varyings, noise, lighting, and distortion step by step.

For blank output, compile failures, or “nothing shows”, read references/black-screen-checklist.md.

3. Match the host, not the idea source

Do not hand over ShaderToy code unchanged if the user asked for Three.js or R3F.

Common translations:

• iTime -> uTime
• iResolution -> uResolution
• fragCoord -> gl_FragCoord.xy
• ShaderToy fullscreen logic -> quad / plane / postprocess host setup

For live previews inside OpenClaw, pair this skill with canvas.

4. Keep answers practical

Prefer responses that include:

• runnable shader code
• required uniforms and defaults
• host-side glue code
• the first debugging step if it fails

Common Uses

• Full-screen effects: flowing gradients, ripples, ShaderToy-style animated backgrounds
• Material effects: fresnel, dissolve, edge glow, scanlines, vertex wobble
• Porting: ShaderToy -> WebGL / Three.js / R3F
• Debugging: black screen, all-white / all-black output, broken UVs, wrong varyings, missing uniforms

Commands

Intake

bash

node {baseDir}/scripts/shader.js intake "fullscreen ocean background in three.js"
node {baseDir}/scripts/shader.js intake "port this shadertoy to r3f" --json

Use this to structure an underspecified request.

Debug

bash

node {baseDir}/scripts/shader.js debug black-screen
node {baseDir}/scripts/shader.js debug uniform
node {baseDir}/scripts/shader.js debug varyings

Effects

bash

node {baseDir}/scripts/shader.js effects

Maps user phrases to likely starter techniques like gradient, noise, fresnel, dissolve, ripple, scanline, and pixelate.

Boilerplate

bash

node {baseDir}/scripts/shader.js boilerplate fresnel
node {baseDir}/scripts/shader.js boilerplate dissolve --json

Returns stage split, likely uniforms, varyings, build order, and common failure points.

Snippet

bash

node {baseDir}/scripts/shader.js snippet fresnel
node {baseDir}/scripts/shader.js snippet ripple --json

Points to the nearest bundled GLSL starter.

Demo

bash

node {baseDir}/scripts/shader.js demo webgl ripple
node {baseDir}/scripts/shader.js demo r3f fresnel --json

Chooses the best bundled runtime template for a target + effect combination.

Scaffold

bash

node {baseDir}/scripts/shader.js scaffold r3f dissolve
node {baseDir}/scripts/shader.js scaffold postprocess scanline --json

Combines the nearest demo, boilerplate, snippet, and first integration steps.

Assets

Bundled templates:

• assets/webgl-fullscreen-demo/index.html
• assets/threejs-material-demo/index.html
• assets/postprocess-demo/index.html
• assets/r3f-demo/App.jsx
• assets/r3f-demo/main.jsx
• assets/r3f-demo/index.html
• assets/r3f-demo/package.json
• assets/r3f-demo/vite.config.js

Bundled snippets:

• assets/snippets/fresnel.md
• assets/snippets/dissolve.md
• assets/snippets/ripple.md
• assets/snippets/scanline.md
• assets/snippets/pixelate.md
• assets/snippets/vertex-wobble.md

Use the postprocess template for screen-space effects. Use the Three.js or R3F templates for mesh/material effects.

References

• references/glsl-quick-reference.md
• references/black-screen-checklist.md
• references/effect-starters-zh.md
• references/snippets.md
• references/runtime-translation.md

Guardrails

• Default to the smallest working shader that proves the effect.
• Use host-friendly uniform names like uTime, uResolution, uMouse, uTexture.
• Do not assume WebGL2 unless the host clearly uses it.
• Do not invent runtime-specific macros or built-ins.
• Call out likely precision, color-space, or postprocess-order bugs explicitly.
• For performance advice, stay directional unless the actual runtime and GPU are known.