WebGL Shaders

Compiling Shaders for the WebGL Backend

Babylon 89,603 's shaders are templates in Effect.ShadersStore, with #include<name> directives. A JavaScript preprocessor inlines includes, unrolls light loops and applies the defines; the engine converts the result to GLSL ES 3.00 and compiles it, in parallel via KHR_parallel_shader_compile where available. The walnut shader:

From Babylon's shader template to the GLSL that WebGL compilesJavaScript
BookNestStore.lightRoom(scene);                                 // Section 7.7.8's lights
engine.runRenderLoop(() => scene.render());
await scene.whenReadyAsync();
console.log(engine.getGlInfo().renderer);
const effect = scene.getMeshByName('bookcaseLeft').subMeshes[0].effect;
const gl = engine._gl;                                          // private: for learning only
const [, compiled] = gl.getAttachedShaders(effect._pipelineContext.program)
  .map((shader) => gl.getShaderSource(shader));
const lines = (text) => text.split('\n');
console.log([effect.rawFragmentSourceCode, effect.fragmentSourceCode, compiled]
  .map((text) => lines(text).length).join(' -> ') + ' lines');
console.log(lines(compiled)
  .filter((l) => /^#version|^in vec3 vP|out vec4|glFragColor=/.test(l)).join('\n'));
Output
BJS - [19:32:59]: Babylon.js v9.28.0 - WebGL2 - Parallel shader compilation
ANGLE (NVIDIA, NVIDIA GeForce GTX 1650 (0x00001F82) Direct3D11 vs_5_0 ps_5_0, D3D11)
344 -> 894 -> 956 lines
#version 300 es
in vec3 vPositionW;
layout(location = 0) out vec4 glFragColor;
glFragColor=color;

engine.getGlInfo() gives the vendor, version and renderer (Debug Extensions). Unrolled cascades and lights took the template from 344 to 894 lines, and the WebGL 2 conversion (varying to in, gl_FragColor to an out) to 956; ANGLE 2,592 then translates it into HLSL. Spector.js 1,619 (Spector.js) shows these sources for any frame.

The walnut shader's journey on WebGL: template lines, preprocessed lines, compiled GLSL ES 3.00 lines and key linesHTMLLive
<!doctype html>
<style>
  body { margin: 0; background: #f7f3ec; font: 13px system-ui, sans-serif; color: #333; }
  canvas { width: 100%; max-width: 600px; height: 250px; display: block; touch-action: none; outline: none; }
  #info { max-width: 600px; margin: 0; padding: 4px 8px; font: 11px monospace; white-space: pre-wrap; }
</style>
<canvas id="view"></canvas>
<pre id="info">Compiling…</pre>
<script src="https://cdn.jsdelivr.net/npm/babylonjs@9.28.0/babylon.js"></script>
<script>
// ---- BookNest's bookstore: the helpers the book keeps in bookstore.js ----
const ROOM = { width: 8, depth: 6, height: 3, wall: 0.15 };
const BOOKS = [
  { id: 1, title: 'The Quiet Harbor', author: 'Mara Ellison', color: '#1f5f8b', pages: 312, price: 14.99, rating: 4.6, inStock: true },
  { id: 2, title: 'Patterns of the Deep Web', author: 'Tomas Reyes', color: '#5b3f99', pages: 428, price: 32.5, rating: 4.4, inStock: true },
  { id: 3, title: 'Salt and Saffron', author: 'Priya Nair', color: '#e09a10', pages: 256, price: 24, rating: 4.8, inStock: false },
  { id: 4, title: 'Small Steps to Big Summits', author: 'Dana Whitfield', color: '#3f7d3a', pages: 198, price: 18.5, rating: 4.3, inStock: true },
  { id: 5, title: "The Clockmaker's Paradox", author: 'Julian Voss', color: '#b5452f', pages: 344, price: 16.75, rating: 4.7, inStock: true },
  { id: 6, title: 'Gardens in Glass', author: 'Lena Hart', color: '#2a9d8f', pages: 176, price: 21.3, rating: 4.5, inStock: true },
];
function createScene(engine) {
  const scene = new BABYLON.Scene(engine);
  scene.clearColor = BABYLON.Color4.FromHexString('#cfd8dcff');
  const sky = new BABYLON.HemisphericLight('sky', new BABYLON.Vector3(0.3, 1, -0.4), scene);
  sky.groundColor = new BABYLON.Color3(0.35, 0.32, 0.3);
  return scene;
}
function paint(scene, name, hex) {                  // a matte color
  const material = new BABYLON.StandardMaterial(name, scene);
  material.diffuseColor = BABYLON.Color3.FromHexString(hex);
  material.specularColor = BABYLON.Color3.Black();
  return material;
}
function createRoom(scene) {                        // floor and three walls, front open
  const room = new BABYLON.TransformNode('room', scene);
  const floor = BABYLON.MeshBuilder.CreateGround('floor', { width: ROOM.width, height: ROOM.depth }, scene);
  floor.material = paint(scene, 'oak', '#b08d6a');
  floor.parent = room;
  const plaster = paint(scene, 'plaster', '#fff3e0');
  for (const [name, width, x, z] of [['backWall', 8, 0, 3], ['leftWall', 6, -4, 0], ['rightWall', 6, 4, 0]]) {
    const wall = BABYLON.MeshBuilder.CreateBox(name, { width, height: ROOM.height, depth: ROOM.wall }, scene);
    wall.position.set(x, ROOM.height / 2, z);
    wall.rotation.y = x ? Math.PI / 2 : 0;
    wall.material = plaster;
    wall.parent = room;
  }
  return room;
}
function createBookcase(scene, name, x) {           // 8 boxes merged into 1 mesh
  const [w, h, d, t] = [3, 2.2, 0.35, 0.04];
  const parts = [[t, h, d, -w / 2, h / 2, 0], [t, h, d, w / 2, h / 2, 0], [w, h, t, 0, h / 2, d / 2 - t / 2]];
  for (let i = 0; i < 5; i++) parts.push([w, t, d, 0, 0.1 + i * 0.5, 0]);
  const bookcase = BABYLON.Mesh.MergeMeshes(parts.map(([width, height, depth, px, py, pz]) => {
    const part = BABYLON.MeshBuilder.CreateBox('part', { width, height, depth }, scene);
    part.position.set(px, py, pz);
    return part;
  }), true);
  bookcase.name = name;
  bookcase.material = paint(scene, 'walnut', '#6d4c33');
  bookcase.position.set(x, 0, ROOM.depth / 2 - ROOM.wall / 2 - d / 2);   // against the back wall
  return bookcase;
}
function drawCover(scene, book) {                   // cover art painted on a canvas
  const tex = new BABYLON.DynamicTexture('cover' + book.id, { width: 256, height: 384 }, scene);
  const c = tex.getContext();
  c.fillStyle = book.color; c.fillRect(0, 0, 256, 384);
  c.fillStyle = 'rgba(0,0,0,0.4)'; c.fillRect(0, 0, 18, 384);         // the dark left edge
  c.strokeStyle = '#fff8e1'; c.lineWidth = 3; c.strokeRect(34, 24, 202, 336);
  c.fillStyle = '#fff8e1'; c.textAlign = 'center'; c.font = 'bold 30px Georgia';
  const lines = [''];
  for (const word of book.title.split(' ')) {
    const test = (lines[lines.length - 1] + ' ' + word).trim();
    if (c.measureText(test).width > 180) lines.push(word); else lines[lines.length - 1] = test;
  }
  lines.forEach((line, i) => c.fillText(line, 135, 110 + i * 38));
  c.font = '20px Georgia'; c.fillText(book.author, 135, 330);
  tex.update();
  return tex;
}
function placeBooks(scene, bookcase, shelf = 2) {   // six books, spines out, covers on +x
  const strip = new BABYLON.Vector4(0, 0, 0.07, 1);
  const faceUV = [strip, strip, new BABYLON.Vector4(0, 0, 1, 1), strip, strip, strip];
  let x = -0.35;                                    // left end of the row, local to the bookcase
  return BOOKS.map((record) => {
    const width = record.pages / 4000 + 0.02;       // spine thickness from page count
    const book = BABYLON.MeshBuilder.CreateBox(`book${record.id}`, { width, height: 0.3, depth: 0.22, faceUV, wrap: true }, scene);
    book.parent = bookcase;
    book.position.set(x + width / 2, 0.12 + shelf * 0.5 + 0.15, -0.02);
    x += width + 0.012;
    book.material = new BABYLON.StandardMaterial(record.title, scene);
    book.material.diffuseTexture = drawCover(scene, record);
    book.material.specularColor = new BABYLON.Color3(0.15, 0.15, 0.15);
    book.metadata = record;                         // the record, for picking
    return book;
  });
}
// The book cuts the storefront with CSG2 (Manifold WebAssembly); this sandbox cannot download
// the .wasm, so the older pure-JavaScript BABYLON.CSG makes the same cuts here.
function createFrontWall(scene) {
  const box = (width, height, depth, x, y) => {
    const mesh = BABYLON.MeshBuilder.CreateBox('cut', { width, height, depth }, scene);
    mesh.position.set(x, y, -ROOM.depth / 2);
    return mesh;
  };
  const solid = box(ROOM.width, ROOM.height, ROOM.wall, 0, ROOM.height / 2);
  const windowHole = box(3.2, 1.6, 1, -1.4, 1.6), doorHole = box(1.1, 2.2, 1, 2.3, 1.1);
  const wall = BABYLON.CSG.FromMesh(solid).subtract(BABYLON.CSG.FromMesh(windowHole))
    .subtract(BABYLON.CSG.FromMesh(doorHole)).toMesh('frontWall', scene.getMaterialByName('plaster'), scene);
  [solid, windowHole, doorHole].forEach((mesh) => mesh.dispose());
  return wall;
}
// ---- end of the bookstore helpers ----

function lightRoom(scene) {                         // call after the meshes exist
  scene.getLightByName('sky').intensity = 0.5;      // the sky light becomes fill light
  const sun = new BABYLON.DirectionalLight('sun', new BABYLON.Vector3(0.2, -0.33, 1), scene);
  sun.intensity = 0.8;
  sun.diffuse = BABYLON.Color3.FromHexString('#fff1d6');   // warm afternoon sun
  const ceiling = BABYLON.MeshBuilder.CreateBox('ceiling', { width: ROOM.width, height: ROOM.wall, depth: ROOM.depth }, scene);
  ceiling.position.y = ROOM.height + ROOM.wall / 2;
  ceiling.layerMask = 0x10000000;                   // no camera draws it; it still casts
  const shadows = new BABYLON.CascadedShadowGenerator(2048, sun);
  Object.assign(shadows, { numCascades: 3, shadowMaxZ: 20, lambda: 1,
    autoCalcDepthBounds: true, bias: 0.002, normalBias: 0.01 });
  for (const mesh of scene.meshes) {
    if (mesh.name !== 'floor') shadows.addShadowCaster(mesh);
    mesh.receiveShadows = true;
  }
  const lamp = new BABYLON.PointLight('lamp', new BABYLON.Vector3(-1.2, 2.3, 1.4), scene);
  lamp.diffuse = BABYLON.Color3.FromHexString('#ffd9a0');
  Object.assign(lamp, { intensity: 0.7, range: 5 });   // a warm reading lamp
  return { sun, lamp, shadows };
}

const canvas = document.getElementById('view');
const engine = new BABYLON.Engine(canvas, true, {}, true);
const scene = createScene(engine);
createRoom(scene);
placeBooks(scene, createBookcase(scene, 'bookcaseLeft', -1.8));
lightRoom(scene);                                    // cascades and lights unroll into the shader
const camera = new BABYLON.ArcRotateCamera('browse', -1.75, 1.4, 3.5, new BABYLON.Vector3(-1.8, 1.2, 2.5), scene);
camera.minZ = 0.05;
camera.attachControl(canvas, true);
engine.runRenderLoop(() => scene.render());

scene.executeWhenReady(() => {
  const effect = scene.getMeshByName('bookcaseLeft').subMeshes[0].effect;
  const gl = engine._gl;                             // private: for learning only
  const [, compiled] = gl.getAttachedShaders(effect._pipelineContext.program).map((shader) => gl.getShaderSource(shader));
  const lines = (text) => text.split('\n');
  document.getElementById('info').textContent = `renderer: ${engine.getGlInfo().renderer}\n` +
    `fragment shader: ${[effect.rawFragmentSourceCode, effect.fragmentSourceCode, compiled].map((t) => lines(t).length).join(' -> ')} lines ` +
    `(template -> preprocessed -> compiled)\n` +
    lines(compiled).filter((l) => /^#version|^in vec3 vP|out vec4|glFragColor=/.test(l)).join('\n');
});
addEventListener('resize', () => engine.resize());
</script>