# shader-glsl

GLSL fragment shader skill for generating animated backgrounds, image transitions, and Three.js ShaderMaterial pipelines.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 1400 installs · ★ 44
- Author: iart-ai
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/iart-ai/webgl-animation-skills/tree/HEAD/skills/shader-glsl/SKILL.md
- Updated: 2026-06-22
- HTML: https://affpapa.org/en/nevibecode/skills/shader-glsl

## What it does

The skill guides writing GPU fragment shaders running parallel pixel calculations. Each fragment shader computes color per pixel. It covers coordinate normalization, aspect correction, Inigo Quilez cosine palettes, and antialiased SDF shapes via `fwidth`. Value noise, hash functions, and multi-octave fbm are included without requiring external textures.

It details transitions between two textures using dissolve thresholds, displacement maps, and glitch effects with chromatic aberration. Integration rules show how to mount a `THREE.ShaderMaterial` onto a `PlaneGeometry(2, 2)` quad. Time passes via `u_time` using `clock.getElapsedTime()`, while vertex shaders bypass projection matrices.

Mobile optimization is a key concern here. Loops must have constant bounds in GLSL ES, and fbm octaves should stay at 5–6 or fewer. Authors advise setting `precision mediump float;` on mobile when `highp` is not required by coordinates. The repo also includes `scripts/seek-shot.sh` to grab frames using a `?t=N` parameter.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add iart-ai/webgl-animation-skills --skill shader-glsl -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/shader-glsl/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/shader-glsl/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add iart-ai/webgl-animation-skills --skill shader-glsl -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/shader-glsl/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add iart-ai/webgl-animation-skills --skill shader-glsl -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/shader-glsl/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install iart-ai/webgl-animation-skills shader-glsl
```

2. **Manually: put the files in place**
- File: `.github/skills/shader-glsl/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add iart-ai/webgl-animation-skills --skill shader-glsl -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/iart-ai/webgl-animation-skills --path skills/shader-glsl
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/shader-glsl/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add iart-ai/webgl-animation-skills --skill shader-glsl -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/iart-ai/webgl-animation-skills/tree/HEAD/skills/shader-glsl/SKILL.md

## When to use it
- write animated gradient or noise backgrounds in GLSL
- wire up a Three.js ShaderMaterial on a full-screen quad
- build texture transitions with noise dissolve or displacement
- implement chromatic aberration and row-based glitch effects
- render crisp SDF circles and boxes with screen-space antialiasing

## Example prompts
- Create an animated plasma background using Three.js ShaderMaterial
- Write a GLSL fragment shader for a noise dissolve transition between two textures
- Add a chromatic aberration glitch shader to this image

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: f9e27c9272f6e3bb.

BEGIN THIRD-PARTY FILE f9e27c9272f6e3bb
````text
---
name: shader-glsl
description: This skill should be used when the user asks to "write a fragment shader", "make a GLSL gradient/noise/plasma background", "create an image transition (dissolve, displacement, glitch)", "add distortion or chromatic aberration", "build an SDF shape shader", "wire up a Three.js ShaderMaterial with uniforms", or "do GPU post-processing". Covers GLSL fragment shaders, noise/fbm, SDFs, domain warping, transitions, and Three.js integration.
version: 0.1.0
---

# Shader / GLSL

Write GPU fragment shaders for generative motion, gradients, transitions, and post-processing. Fragment shaders run once per pixel in parallel — the most performant way to do full-screen generative motion.

## When to use

- Animated gradient, noise, plasma, or aurora backgrounds.
- Image transitions: dissolve, displacement, glitch, ripple, wipe.
- Distortion, chromatic aberration, generative patterns, SDF shapes.
- Post-processing passes over a rendered scene.

## Fragment shader skeleton

Every fragment shader computes a color for one pixel. Normalize coordinates, aspect-correct, then build color.

```glsl
precision highp float;
uniform float u_time;
uniform vec2  u_resolution;
uniform vec2  u_mouse;

void main() {
  vec2 uv = gl_FragCoord.xy / u_resolution.xy;     // 0..1
  vec2 p  = uv * 2.0 - 1.0;                         // -1..1, centered
  p.x *= u_resolution.x / u_resolution.y;           // aspect-correct
  vec3 col = 0.5 + 0.5 * cos(u_time + p.xyx + vec3(0.0, 2.0, 4.0));
  gl_FragColor = vec4(col, 1.0);
}
```

The cosine-palette line above (Inigo Quilez palettes) is the fastest route to a good-looking animated gradient: `a + b*cos(2π*(c*t + d))` with tunable `a,b,c,d` vec3s.

## Core building blocks

**smoothstep + mix** are the workhorses. `smoothstep(e0, e1, x)` gives a smooth 0→1 ramp; `mix(a, b, t)` linearly blends. Antialias an edge by the width of one pixel:
```glsl
float px = fwidth(d);                    // screen-space derivative
float mask = smoothstep(px, -px, d);     // crisp AA edge from SDF distance d
```

**Hash + value noise** (no textures needed):
```glsl
float hash(vec2 p){ return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453); }
float noise(vec2 p){
  vec2 i = floor(p), f = fract(p);
  vec2 u = f * f * (3.0 - 2.0 * f);                // smooth interpolation
  return mix(mix(hash(i), hash(i + vec2(1,0)), u.x),
             mix(hash(i + vec2(0,1)), hash(i + vec2(1,1)), u.x), u.y);
}
float fbm(vec2 p){                                  // fractal noise, organic
  float v = 0.0, a = 0.5;
  for (int i = 0; i < 5; i++){ v += a * noise(p); p *= 2.0; a *= 0.5; }
  return v;
}
```
````
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