An ActionManager on a mesh runs actions (ExecuteCodeAction, SetValueAction, InterpolateValueAction, PlayAnimationAction...) on triggers (OnPickTrigger, OnPointerOverTrigger, OnPointerOutTrigger, OnLongPressTrigger, OnIntersectionEnterTrigger, and scene-level key triggers). Here a spine grows on hover and reports a pick, scene.simulatePointer* standing in for a mouse; the next three listings reuse this shelf and camera:
const books = BookNestStore.placeBooks(scene, BookNestStore.createBookcase(scene, 'case', 0));
const target = new BABYLON.Vector3(0, 1.3, 2.6);
const camera = new BABYLON.ArcRotateCamera('browse', -Math.PI / 2, 1.5, 2.5, target, scene);
engine.runRenderLoop(() => scene.render());
await scene.whenReadyAsync();
const { OnPointerOverTrigger, OnPickTrigger } = BABYLON.ActionManager;
const book = books[2];
book.actionManager = new BABYLON.ActionManager(scene);
book.actionManager.registerAction(new BABYLON.InterpolateValueAction(OnPointerOverTrigger,
book, 'scaling', new BABYLON.Vector3(1.15, 1.15, 1.15), 200)); // 200 ms tween
book.actionManager.registerAction(new BABYLON.ExecuteCodeAction(OnPickTrigger,
(event) => console.log(`picked ${event.source.metadata.title}`)));
const hit = scene.pick(view.clientWidth / 2, view.clientHeight / 2); // the canvas center
scene.simulatePointerMove(hit); // hover: starts the tween
scene.simulatePointerDown(hit);
scene.simulatePointerUp(hit); // a click: OnPickTriggerOutput
picked Salt and Saffron
Actions serialize, which suits editors, but most applications handle pointer events in code.
<!doctype html>
<style>
body { margin: 0; background: #f7f3ec; font: 13px system-ui, sans-serif; color: #333; }
canvas { width: 100%; max-width: 600px; height: 300px; display: block; touch-action: none; outline: none; }
#log { max-width: 600px; padding: 4px 8px; font-size: 14px; }
</style>
<canvas id="view"></canvas>
<div id="log">Hover over a spine, then click it.</div>
<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 ----
const canvas = document.getElementById('view');
const engine = new BABYLON.Engine(canvas, true, {}, true);
const scene = createScene(engine);
const books = placeBooks(scene, createBookcase(scene, 'case', 0));
const target = new BABYLON.Vector3(0, 1.3, 2.6);
const camera = new BABYLON.ArcRotateCamera('browse', -Math.PI / 2, 1.5, 1.6, target, scene);
camera.minZ = 0.05;
camera.attachControl(canvas, true);
engine.runRenderLoop(() => scene.render());
const log = document.getElementById('log');
const { OnPointerOverTrigger, OnPointerOutTrigger, OnPickTrigger } = BABYLON.ActionManager;
for (const book of books) {
book.actionManager = new BABYLON.ActionManager(scene);
book.actionManager.registerAction(new BABYLON.InterpolateValueAction(OnPointerOverTrigger,
book, 'scaling', new BABYLON.Vector3(1.15, 1.15, 1.15), 200)); // 200 ms tween
book.actionManager.registerAction(new BABYLON.InterpolateValueAction(OnPointerOutTrigger,
book, 'scaling', new BABYLON.Vector3(1, 1, 1), 200));
book.actionManager.registerAction(new BABYLON.ExecuteCodeAction(OnPickTrigger,
(event) => { log.textContent = `picked ${event.source.metadata.title}`; }));
}
// Stand in for a mouse once, so the preview shows the actions firing
scene.executeWhenReady(() => {
scene.render();
const center = books[2].getBoundingInfo().boundingBox.centerWorld;
const aim = center.subtract(camera.position).normalize();
const hit = scene.pickWithRay(new BABYLON.Ray(camera.position, aim));
scene.simulatePointerMove(hit); // hover: starts the tween
scene.simulatePointerDown(hit);
scene.simulatePointerUp(hit); // a click: OnPickTrigger
});
addEventListener('resize', () => engine.resize());
</script>