ck:shader

Guidance for writing GLSL fragment shaders, small GPU programs that calculate the color of each pixel to create graphics and effects.

In plain words
What is it for?
Use it for procedural art, WebGL or Three.js effects, custom textures, noise patterns, and animated visual effects.
Why use it?
It helps replace manually drawn images with code-generated shapes, patterns, textures, gradients, and animation.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/manhvann/codexkit/shader
Any agent
npx skills add manhvann/codexkit --skill shader
Clone the repo
git clone --depth 1 https://github.com/manhvann/codexkit

Made for: Claude Code, Codex.

Per session 65 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,133 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00065 $0.01133
Opus 5 $0.00032 $0.00566
Sonnet 5 $0.00013 $0.00227
Haiku 4.5 $0.00006 $0.00113

Measured 2d ago against content hash 5cd90f8c61f4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

ck:shader scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/skills/shader/SKILL.md · 114 lines

How it starts

The opening of the file, as written. The whole thing — 114 lines — stays where its author put it; the contents beside it link to each section on GitHub.

GLSL Fragment Shaders

Write GPU-accelerated fragment shaders for procedural graphics, textures, and visual effects.

When to Use

  • Creating procedural textures (wood, marble, clouds, terrain)
  • Drawing shapes with distance fields (SDF)
  • Generating patterns, noise, gradients
  • Building visual effects and animations
  • Writing custom shaders for Three.js, WebGL, Processing

Core Concepts

Fragment shaders execute simultaneously on every pixel. Each thread:

  • Receives pixel position via gl_FragCoord
  • Returns color via gl_FragColor (vec4: RGBA 0.0-1.0)
  • Cannot communicate with other threads (stateless)

Standard Uniforms

uniform float u_time;       // Elapsed seconds
uniform vec2 u_resolution;  // Canvas size (width, height)
uniform vec2 u_mouse;       // Mouse position in pixels

Normalize coordinates: vec2 st = gl_FragCoord.xy / u_resolution;

Essential Functions

Function Purpose Example
mix(a,b,t) Linear interpolate mix(red, blue, 0.5)
step(edge,x) Hard threshold step(0.5, st.x)
smoothstep(e0,e1,x) Smooth threshold smoothstep(0.2, 0.8, st.x)
fract(x) Fractional part fract(st * 3.0) for tiling
mod(x,y) Modulo mod(st.x, 0.25)
clamp(x,min,max) Constrain value clamp(col, 0.0, 1.0)
length(v) Vector magnitude length(st - 0.5)
distance(a,b) Euclidean distance distance(st, center)
dot(a,b) Dot product dot(normal, lightDir)
normalize(v) Unit vector normalize(direction)
atan(y,x) Angle (radians) atan(st.y-0.5, st.x-0.5)
sin/cos/pow/abs Math Hardware-accelerated

Quick Patterns

Circle:

float d = distance(st, vec2(0.5));
float circle = 1.0 - smoothstep(0.2, 0.21, d);

Rectangle:

vec2 bl = step(vec2(0.1), st);
vec2 tr = step(vec2(0.1), 1.0 - st);
float rect = bl.x * bl.y * tr.x * tr.y;

Tiling:

st = fract(st * 4.0);  // 4x4 grid

Read the full file on GitHub · 114 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 114 lines · 65 tokens per session scan A 5cd90f8c61f4

Subscribe to this mod's changes

ck:shader is a skill published in the GitHub repository manhvann/codexkit (88 stars, last pushed 4d ago), licensed MIT. It adds 65 tokens to every session and 1,133 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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