GLSL ShaderMaterial

Writing a ShaderMaterial in GLSL

A ShaderMaterial compiles your vertex and fragment shaders as GLSL ES 3.00 (Statements and Built-ins), after a prefix that declares position, normal, uv, modelViewMatrix, projectionMatrix and friends, and maps GLSL 1 names such as texture2D and gl_FragColor to their 3.00 forms. Your own values go in uniforms, each a { value } object. BookNest's featured cover gets a foil sheen, a bright diagonal band that sweeps across it:

bookshelf.js: foilMaterial(), an unlit GLSL cover with a moving sheenJavaScript
export function foilMaterial(map) {
  return new THREE.ShaderMaterial({
    uniforms: { map: { value: map }, time: { value: 0 } },
    vertexShader: /* glsl */ `
      varying vec2 vUv;
      void main() {                                   // uv, position and both matrices
        vUv = uv;                                     // are declared by Three.js
        gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
      }`,
    fragmentShader: /* glsl */ `
      uniform sampler2D map;
      uniform float time;
      varying vec2 vUv;
      void main() {
        vec3 art = texture2D(map, vUv).rgb;           // sRGB texture, decoded to linear
        float sweep = vUv.x + vUv.y - fract(time * 0.25) * 2.5 + 0.2;
        float band = smoothstep(0.12, 0.0, abs(sweep));
        gl_FragColor = vec4(art + band * vec3(0.9, 0.8, 0.5), 1.0);
        #include <tonemapping_fragment>
        #include <colorspace_fragment>
      }`,
  });
}

The two #include chunks, from the THREE.ShaderChunk library the built-in materials are assembled from, matter: textures decode to linear values, so without colorspace_fragment the cover reaches the sRGB canvas too dark. RawShaderMaterial injects nothing at all.

A GLSL ShaderMaterial sweeps a foil sheen across Salt and Saffron's coverHTMLLive
<!doctype html>
<style>
  body { margin: 0; background: #f5f1e8; font: 13px system-ui, sans-serif; color: #263238; }
  canvas { display: block; max-width: 100%; }
  .ui { padding: 4px 8px; }
</style>
<script type="importmap">
{ "imports": {
  "three": "https://cdn.jsdelivr.net/npm/three@0.186.1/build/three.module.js",
  "three/addons/": "https://cdn.jsdelivr.net/npm/three@0.186.1/examples/jsm/" } }
</script>
<div class="ui"><label><input type="checkbox" id="chunks" checked> include colorspace_fragment</label> (off: the cover reaches the sRGB canvas too dark)</div>
<script type="module">
import * as THREE from 'three';
import { mergeGeometries } from 'three/addons/utils/BufferGeometryUtils.js';

const BOOKS = [
  { title: 'The Quiet Harbor', author: 'Elena Marsh', color: '#1f5f8b', rating: 4.6, pages: 312 },
  { title: 'Patterns of the Deep Web', author: 'Ravi Menon', color: '#5b3f99', rating: 4.3, pages: 428 },
  { title: 'Salt and Saffron', author: 'Leila Haddad', color: '#e09a10', rating: 4.8, pages: 256 },
  { title: 'Small Steps to Big Summits', author: 'Tom Okafor', color: '#3f7d3a', rating: 4.1, pages: 198 },
  { title: "The Clockmaker's Paradox", author: 'Iris Vale', color: '#b5452f', rating: 4.5, pages: 344 },
  { title: 'Gardens in Glass', author: 'June Park', color: '#2a9d8f', rating: 4.4, pages: 176 },
];

// --- Book model: pages, two boards and a curved spine, merged with one group per part ---
const thickness = (book) => 0.05 + book.pages * 0.0003;          // metres, from the page count
function bookGeometry(book, height, depth = 0.62) {
  const t = thickness(book), b = 0.012, y = height / 2, z = -depth / 2;
  const box = (w, h, d, x, zz = z) => new THREE.BoxGeometry(w, h, d).translate(x, y, zz);
  const spine = new THREE.CylinderGeometry(t / 2, t / 2, height, 24, 1, true, -Math.PI / 2, Math.PI)
    .scale(1, 1, 0.5).translate(0, y, 0);
  return mergeGeometries([box(t - 2 * b, height - 0.03, depth - 0.02, 0, z + 0.01),
    box(b, height, depth, (b - t) / 2), box(b, height, depth, (t - b) / 2), spine], true);
}
function paint(book, width, height, draw) {
  const canvas = Object.assign(document.createElement('canvas'), { width, height });
  const g = canvas.getContext('2d');
  g.fillStyle = book.color;  g.fillRect(0, 0, width, height);
  g.fillStyle = '#ffffff';
  draw(g);
  const texture = new THREE.CanvasTexture(canvas);
  texture.colorSpace = THREE.SRGBColorSpace;
  return texture;
}
const coverArt = (book) => paint(book, 360, 520, (g) => {
  g.font = 'bold 50px Georgia, serif';
  book.title.split(' ').forEach((word, i) => g.fillText(word, 28, 84 + i * 56, 304));
  g.font = 'italic 28px Georgia, serif';
  g.fillText(`${book.author}, ${book.rating} / 5`, 28, 460);
});
const spineArt = (book) => paint(book, 128, 640, (g) => {
  g.rotate(Math.PI / 2);
  g.textBaseline = 'middle';
  g.font = 'bold 44px Georgia, serif';
  g.fillText(book.title, 24, -64, 440);
  g.font = '28px Georgia, serif';
  g.fillText(book.author.split(' ').at(-1), 490, -64, 130);
});
function createSpineBook(book, height = 0.9) {
  const material = (options) => new THREE.MeshStandardMaterial({ roughness: 0.6, ...options });
  const mesh = new THREE.Mesh(bookGeometry(book, height), [material({ color: '#f3ecdc' }),
    material({ color: book.color }), material({ map: coverArt(book) }), material({ map: spineArt(book) })]);
  return Object.assign(mesh, { name: book.title, userData: { book } });
}

// --- The arrangement ---
function createBookcase() {
  const bookcase = new THREE.Group();
  const plank = new THREE.Mesh(new THREE.BoxGeometry(3.5, 0.06, 0.8), new THREE.MeshStandardMaterial({ color: '#8d6e63' }));
  plank.name = 'plank';
  plank.position.set(0, -0.52, 0);
  bookcase.add(plank);
  const top = BOOKS.reduce((best, book) => (book.rating > best.rating ? book : best));
  let x = -0.85;
  BOOKS.forEach((book, i) => {
    const mesh = createSpineBook(book, 0.84 + 0.05 * (i % 3));   // three trim heights
    if (book === top) {
      mesh.position.set(0.3, -0.49, 0.05);
      mesh.rotation.y = -Math.PI / 2 + 0.35;                     // cover forward, turned a little
    } else {
      mesh.position.set(x + thickness(book) / 2, -0.49, 0.3);    // running x plus half a thickness
      x += thickness(book) + 0.005;
    }
    bookcase.add(mesh);
  });
  return bookcase;
}

// uv, position and both matrices are declared by Three.js in front of your code
function foilMaterial(map, withColorSpace = true) {
  return new THREE.ShaderMaterial({
    uniforms: { map: { value: map }, time: { value: 0 } },
    vertexShader: /* glsl */ `
      varying vec2 vUv;
      void main() {
        vUv = uv;
        gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
      }`,
    fragmentShader: /* glsl */ `
      uniform sampler2D map;
      uniform float time;
      varying vec2 vUv;
      void main() {
        vec3 art = texture2D(map, vUv).rgb;           // sRGB texture, decoded to linear
        float sweep = vUv.x + vUv.y - fract(time * 0.25) * 2.5 + 0.2;
        float band = smoothstep(0.12, 0.0, abs(sweep));
        gl_FragColor = vec4(art + band * vec3(0.9, 0.8, 0.5), 1.0);
        #include <tonemapping_fragment>
        ${withColorSpace ? '#include <colorspace_fragment>' : ''}
      }`,
  });
}

const renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setPixelRatio(Math.min(devicePixelRatio, 2));
renderer.setSize(600, 280);
document.body.prepend(renderer.domElement);
const scene = new THREE.Scene();
scene.background = new THREE.Color('#fbf8f2');
const camera = new THREE.PerspectiveCamera(35, 600 / 280, 0.1, 50);
camera.position.set(0, 0.45, 1.9);
camera.lookAt(0, 0.42, 0);
scene.add(new THREE.HemisphereLight('#ffffff', '#8d6e63', 1.4));
const sun = new THREE.DirectionalLight('#ffffff', 2);
sun.position.set(1, 2, 3);
scene.add(sun);

// Two copies of the book: plain (left) and foil (right)
const plain = createSpineBook(BOOKS[2], 0.9);
const foiled = createSpineBook(BOOKS[2], 0.9);
const map = foiled.material[2].map;
const materials = { on: foilMaterial(map, true), off: foilMaterial(map, false) };
foiled.material[2] = materials.on;                   // group 2: the front board
[plain, foiled].forEach((book, i) => {
  book.position.x = i ? 0.35 : -0.5;
  book.rotation.y = -Math.PI / 2 + 0.25;             // cover toward the camera
  scene.add(book);
});
document.getElementById('chunks').addEventListener('change', (e) => {
  foiled.material[2] = e.target.checked ? materials.on : materials.off;
});

renderer.setAnimationLoop((time) => {
  materials.on.uniforms.time.value = materials.off.uniforms.time.value = time / 1000;   // seconds
  renderer.render(scene, camera);
});
</script>