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Three.js Shaders – Agent Skill by CloudAI-X • Craftwork
Custom GLSL in Three.js: ShaderMaterial, uniforms and common effect patterns.
$ npx skills add https://craftwork.design/skills/threejs-shaders -a claude-code -y
SKILL.md
Quick Start
import * as THREE from "three";
const material = new THREE.ShaderMaterial({
uniforms: {
time: { value: 0 },
color: { value: new THREE.Color(0xff0000) },
},
vertexShader: `
void main() {
gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
}
`,
fragmentShader: `
uniform vec3 color;
void main() {
gl_FragColor = vec4(color, 1.0);
}
`,
});
// Update in animation loop
material.uniforms.time.value = clock.getElapsedTime();
ShaderMaterial vs RawShaderMaterial
ShaderMaterial
Three.js provides built-in uniforms and attributes.
const material = new THREE.ShaderMaterial({
vertexShader: `
// Built-in uniforms available:
// uniform mat4 modelMatrix;
// uniform mat4 modelViewMatrix;
// uniform mat4 projectionMatrix;
// uniform mat4 viewMatrix;
// uniform mat3 normalMatrix;
// uniform vec3 cameraPosition;
// Built-in attributes available:
// attribute vec3 position;
// attribute vec3 normal;
// attribute vec2 uv;
void main() {
gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
}
`,
fragmentShader: `
void main() {
gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}
`,
});
RawShaderMaterial
Full control - you define everything.
const material = new THREE.RawShaderMaterial({
uniforms: {
projectionMatrix: { value: camera.projectionMatrix },
modelViewMatrix: { value: new THREE.Matrix4() },
},
vertexShader: `
precision highp float;
attribute vec3 position;
uniform mat4 projectionMatrix;
uniform mat4 modelViewMatrix;
void main() {
gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
}
`,
fragmentShader: `
precision highp float;
void main() {
gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}
`,
});
const material = new THREE.ShaderMaterial({
uniforms: {
// Numbers
floatValue: { value: 1.5 },
intValue: { value: 1 },
// Vectors
vec2Value: { value: new THREE.Vector2(1, 2) },
vec3Value: { value: new THREE.Vector3(1, 2, 3) },
vec4Value: { value: new THREE.Vector4(1, 2, 3, 4) },
// Colors (converted to vec3)
colorValue: { value: new THREE.Color(0xff0000) },
// Matrices
mat3Value: { value: new THREE.Matrix3() },
mat4Value: { value: new THREE.Matrix4() },
// Textures
textureValue: { value: texture },
cubeTextureValue: { value: cubeTexture },
// Arrays
floatArray: { value: [1.0, 2.0, 3.0] },
vec3Array: {
value: [new THREE.Vector3(1, 0, 0), new THREE.Vector3(0, 1, 0)],
},
},
});
GLSL Declarations // In shader
uniform float floatValue;
uniform int intValue;
uniform vec2 vec2Value;
uniform vec3 vec3Value;
uniform vec3 colorValue; // Color becomes vec3
uniform vec4 vec4Value;
uniform mat3 mat3Value;
uniform mat4 mat4Value;
uniform sampler2D textureValue;
uniform samplerCube cubeTextureValue;
uniform float floatArray[3];
uniform vec3 vec3Array[2];
// Direct assignment
material.uniforms.time.value = clock.getElapsedTime();
// Vector/Color updates
material.uniforms.position.value.set(x, y, z);
material.uniforms.color.value.setHSL(hue, 1, 0.5);
// Matrix updates
material.uniforms.matrix.value.copy(mesh.matrixWorld);
Varyings Pass data from vertex to fragment shader.
const material = new THREE.ShaderMaterial({
vertexShader: `
varying vec2 vUv;
varying vec3 vNormal;
varying vec3 vPosition;
void main() {
vUv = uv;
vNormal = normalize(normalMatrix * normal);
vPosition = (modelViewMatrix * vec4(position, 1.0)).xyz;
gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
}
`,
fragmentShader: `
varying vec2 vUv;
varying vec3 vNormal;
varying vec3 vPosition;
void main() {
// Use interpolated values
gl_FragColor = vec4(vNormal * 0.5 + 0.5, 1.0);
}
`,
});
Common Shader Patterns
Texture Sampling const material = new THREE.ShaderMaterial({
uniforms: {
map: { value: texture },
},
vertexShader: `
varying vec2 vUv;
void main() {
vUv = uv;
gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
}
`,
fragmentShader: `
uniform sampler2D map;
varying vec2 vUv;
void main() {
vec4 texColor = texture2D(map, vUv);
gl_FragColor = texColor;
}
`,
});
Vertex Displacement const material = new THREE.ShaderMaterial({
uniforms: {
time: { value: 0 },
amplitude: { value: 0.5 },
},
vertexShader: `
uniform float time;
uniform float amplitude;
void main() {
vec3 pos = position;
// Wave displacement
pos.z += sin(pos.x * 5.0 + time) * amplitude;
pos.z += sin(pos.y * 5.0 + time) * amplitude;
gl_Position = projectionMatrix * modelViewMatrix * vec4(pos, 1.0);
}
`,
fragmentShader: `
void main() {
gl_FragColor = vec4(0.5, 0.8, 1.0, 1.0);
}
`,
});
Fresnel Effect const material = new THREE.ShaderMaterial({
vertexShader: `
varying vec3 vNormal;
varying vec3 vWorldPosition;
void main() {
vNormal = normalize(normalMatrix * normal);
vWorldPosition = (modelMatrix * vec4(position, 1.0)).xyz;
gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
}
`,
fragmentShader: `
varying vec3 vNormal;
varying vec3 vWorldPosition;
void main() {
// cameraPosition is auto-provided by ShaderMaterial
vec3 viewDirection = normalize(cameraPosition - vWorldPosition);
float fresnel = pow(1.0 - dot(viewDirection, vNormal), 3.0);
vec3 baseColor = vec3(0.0, 0.0, 0.5);
vec3 fresnelColor = vec3(0.5, 0.8, 1.0);
gl_FragColor = vec4(mix(baseColor, fresnelColor, fresnel), 1.0);
}
`,
});
Noise-Based Effects // Simple noise function
float random(vec2 st) {
return fract(sin(dot(st.xy, vec2(12.9898, 78.233))) * 43758.5453);
}
// Value noise
float noise(vec2 st) {
vec2 i = floor(st);
vec2 f = fract(st);
float a = random(i);
float b = random(i + vec2(1.0, 0.0));
float c = random(i + vec2(0.0, 1.0));
float d = random(i + vec2(1.0, 1.0));
vec2 u = f * f * (3.0 - 2.0 * f);
return mix(a, b, u.x) + (c - a) * u.y * (1.0 - u.x) + (d - b) * u.x * u.y;
}
// Usage
float n = noise(vUv * 10.0 + time);
Gradient // Linear gradient
vec3 color = mix(colorA, colorB, vUv.y);
// Radial gradient
float dist = distance(vUv, vec2(0.5));
vec3 color = mix(centerColor, edgeColor, dist * 2.0);
// Smooth gradient with custom curve
float t = smoothstep(0.0, 1.0, vUv.y);
vec3 color = mix(colorA, colorB, t);
Rim Lighting const material = new THREE.ShaderMaterial({
vertexShader: `
varying vec3 vNormal;
varying vec3 vViewPosition;
void main() {
vNormal = normalize(normalMatrix * normal);
vec4 mvPosition = modelViewMatrix * vec4(position, 1.0);
vViewPosition = mvPosition.xyz;
gl_Position = projectionMatrix * mvPosition;
}
`,
fragmentShader: `
varying vec3 vNormal;
varying vec3 vViewPosition;
void main() {
vec3 viewDir = normalize(-vViewPosition);
float rim = 1.0 - max(0.0, dot(viewDir, vNormal));
rim = pow(rim, 4.0);
vec3 baseColor = vec3(0.2, 0.2, 0.8);
vec3 rimColor = vec3(1.0, 0.5, 0.0);
gl_FragColor = vec4(baseColor + rimColor * rim, 1.0);
}
`,
});
Dissolve Effect uniform float progress;
uniform sampler2D noiseMap;
void main() {
float noise = texture2D(noiseMap, vUv).r;
if (noise < progress) {
discard;
}
// Edge glow
float edge = smoothstep(progress, progress + 0.1, noise);
vec3 edgeColor = vec3(1.0, 0.5, 0.0);
vec3 baseColor = vec3(0.5);
gl_FragColor = vec4(mix(edgeColor, baseColor, edge), 1.0);
}
Extending Built-in Materials
onBeforeCompile Modify existing material shaders.
const material = new THREE.MeshStandardMaterial({ color: 0x00ff00 });
material.onBeforeCompile = (shader) => {
// Add custom uniform
shader.uniforms.time = { value: 0 };
// Store reference for updates
material.userData.shader = shader;
// Modify vertex shader
shader.vertexShader = shader.vertexShader.replace(
"#include <begin_vertex>",
`
#include <begin_vertex>
transformed.y += sin(position.x * 10.0 + time) * 0.1;
`,
);
// Add uniform declaration
shader.vertexShader = "uniform float time;\n" + shader.vertexShader;
};
// Update in animation loop
if (material.userData.shader) {
material.userData.shader.uniforms.time.value = clock.getElapsedTime();
}
Common Injection Points // Vertex shader chunks
"#include <begin_vertex>"; // After position is calculated
"#include <project_vertex>"; // After gl_Position
"#include <beginnormal_vertex>"; // Normal calculation start
// Fragment shader chunks
"#include <color_fragment>"; // After diffuse color
"#include <output_fragment>"; // Final output
"#include <fog_fragment>"; // After fog applied
GLSL Built-in Functions
Math Functions // Basic
abs(x), sign(x), floor(x), ceil(x), fract(x)
mod(x, y), min(x, y), max(x, y), clamp(x, min, max)
mix(a, b, t), step(edge, x), smoothstep(edge0, edge1, x)
// Trigonometry
sin(x), cos(x), tan(x)
asin(x), acos(x), atan(y, x), atan(x)
radians(degrees), degrees(radians)
// Exponential
pow(x, y), exp(x), log(x), exp2(x), log2(x)
sqrt(x), inversesqrt(x)
Vector Functions // Length and distance
length(v), distance(p0, p1), dot(x, y), cross(x, y)
// Normalization
normalize(v)
// Reflection and refraction
reflect(I, N), refract(I, N, eta)
// Component-wise
lessThan(x, y), lessThanEqual(x, y)
greaterThan(x, y), greaterThanEqual(x, y)
equal(x, y), notEqual(x, y)
any(bvec), all(bvec)
Texture Functions // GLSL 1.0 (default) - use texture2D/textureCube
texture2D(sampler, coord)
texture2D(sampler, coord, bias)
textureCube(sampler, coord)
// GLSL 3.0 (glslVersion: THREE.GLSL3) - use texture()
// texture(sampler, coord) replaces texture2D/textureCube
// Also use: out vec4 fragColor instead of gl_FragColor
// Texture size (GLSL 1.30+)
textureSize(sampler, lod)
Common Material Properties const material = new THREE.ShaderMaterial({
uniforms: {
/* ... */
},
vertexShader: "/* ... */",
fragmentShader: "/* ... */",
// Rendering
transparent: true,
opacity: 1.0,
side: THREE.DoubleSide,
depthTest: true,
depthWrite: true,
// Blending
blending: THREE.NormalBlending,
// AdditiveBlending, SubtractiveBlending, MultiplyBlending
// Wireframe
wireframe: false,
wireframeLinewidth: 1, // Note: >1 has no effect on most platforms (WebGL limitation)
// Extensions
extensions: {
derivatives: true, // For fwidth, dFdx, dFdy
fragDepth: true, // gl_FragDepth
drawBuffers: true, // Multiple render targets
shaderTextureLOD: true, // texture2DLod
},
// GLSL version
glslVersion: THREE.GLSL3, // For WebGL2 features
});
Shader Includes
Using Three.js Shader Chunks import { ShaderChunk } from "three";
const fragmentShader = `
${ShaderChunk.common}
${ShaderChunk.packing}
uniform sampler2D depthTexture;
varying vec2 vUv;
void main() {
float depth = texture2D(depthTexture, vUv).r;
float linearDepth = perspectiveDepthToViewZ(depth, 0.1, 1000.0);
gl_FragColor = vec4(vec3(-linearDepth / 100.0), 1.0);
}
`;
External Shader Files // With vite/webpack
import vertexShader from "./shaders/vertex.glsl";
import fragmentShader from "./shaders/fragment.glsl";
const material = new THREE.ShaderMaterial({
vertexShader,
fragmentShader,
});
Instanced Shaders // Instanced attribute
const offsets = new Float32Array(instanceCount * 3);
// Fill offsets...
geometry.setAttribute("offset", new THREE.InstancedBufferAttribute(offsets, 3));
const material = new THREE.ShaderMaterial({
vertexShader: `
attribute vec3 offset;
void main() {
vec3 pos = position + offset;
gl_Position = projectionMatrix * modelViewMatrix * vec4(pos, 1.0);
}
`,
fragmentShader: `
void main() {
gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}
`,
});
Debugging Shaders // Check for compile errors
material.onBeforeCompile = (shader) => {
console.log("Vertex Shader:", shader.vertexShader);
console.log("Fragment Shader:", shader.fragmentShader);
};
// Visual debugging
fragmentShader: `
void main() {
// Debug UV
gl_FragColor = vec4(vUv, 0.0, 1.0);
// Debug normals
gl_FragColor = vec4(vNormal * 0.5 + 0.5, 1.0);
// Debug position
gl_FragColor = vec4(vPosition * 0.1 + 0.5, 1.0);
}
`;
// Check WebGL errors
renderer.debug.checkShaderErrors = true;
Minimize uniforms : Group related values into vectorsAvoid conditionals : Use mix/step instead of if/elsePrecalculate : Move calculations to JS when possibleUse textures : For complex functions, use lookup tablesLimit overdraw : Avoid transparent objects when possible // Instead of:
if (value > 0.5) {
color = colorA;
} else {
color = colorB;
}
// Use:
color = mix(colorB, colorA, step(0.5, value));
See Also
threejs-materials - Built-in material typesthreejs-postprocessing - Full-screen shader effectsthreejs-textures - Texture sampling in shaders 36 ShaderToy-style GLSL techniques, including signed distance fields, ray marching, fluids, noise and post-processing, with a routing table.
