The camera already has its ellipsoid, gravity and keys; openStore's next two lines put it on the sidewalk at (2.3, 1.6, -5), facing the door. The CSG wall, sidewalk, bookcases and table all check collisions. To test them without a keyboard, a page can do what a held arrow key does and feed the camera a step through cameraDirection, which passes through the collision system:
const { scene, camera } = await BookNestStore.openStore(engine, view);
engine.runRenderLoop(() => scene.render());
for (const [place, x] of [['door', 2.3], ['window', -1.4]]) {
camera.position.set(x, 1.6, -5); // on the sidewalk, facing the shop
camera.setTarget(new BABYLON.Vector3(x, 1.6, 0));
const step = scene.onBeforeRenderObservable.add(() => // "forward" held down, in code:
camera.cameraDirection.set(0, 0, 0.025)); // 2.5 cm a frame, 1.5 m/s
await new Promise((done) => setTimeout(done, 5000));
scene.onBeforeRenderObservable.remove(step);
const at = camera.position.asArray().map((v) => v.toFixed(2)).join(', ');
console.log(`toward the ${place}: stopped at (${at})`);
}Output
toward the door: stopped at (2.30, 1.61, 2.28) toward the window: stopped at (-1.40, 1.61, -3.38)
Through the door, the visitor crossed the shop and stopped 0.3 m, the ellipsoid's radius, short of the right bookcase (z 2.575); at the window the wall's outer face (z -3.075) stopped them. The window is as tall as the ellipsoid, but FreeCamera hangs the ellipsoid below the eye, from the floor to 1.6 m, so the sill blocks it.
<!doctype html>
<style>
body { margin: 0; background: #f7f3ec; font: 13px system-ui, sans-serif; color: #333; }
canvas { width: 100%; max-width: 600px; height: 320px; display: block; touch-action: none; outline: none; }
#info { max-width: 600px; margin: 0; padding: 4px 8px; font-family: monospace; white-space: pre-wrap; }
</style>
<canvas id="view"></canvas>
<pre id="info"></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 createWalkCamera(scene, canvas) { // walk at eye height
const start = new BABYLON.Vector3(0, 1.6, -2.2); // eye height, near the open front
const camera = new BABYLON.UniversalCamera('walk', start, scene);
camera.setTarget(new BABYLON.Vector3(0, 1.4, 3));
Object.assign(camera, {
minZ: 0.05, // the default 1 m clips nearby shelves
speed: 0.05, angularSensibility: 4000, // about 1.6 m/s, slower mouse look
ellipsoid: new BABYLON.Vector3(0.3, 0.8, 0.3), // a visitor 1.6 m tall, 0.6 m wide
checkCollisions: true, applyGravity: true,
needMoveForGravity: true, // fall even while no key is held
});
camera.keysUp.push(87); camera.keysDown.push(83); // W and S beside the arrows
camera.keysLeft.push(65); camera.keysRight.push(68); // A and D
scene.gravity = new BABYLON.Vector3(0, -9.81 / 60, 0); // units per frame, not m/s^2
scene.collisionsEnabled = true;
const size = { width: ROOM.width, height: ROOM.height, depth: ROOM.wall };
const glass = BABYLON.MeshBuilder.CreateBox('frontCollider', size, scene);
glass.position.set(0, ROOM.height / 2, -ROOM.depth / 2);
glass.isVisible = false; // the open front still stops you
for (const name of ['floor', 'backWall', 'leftWall', 'rightWall', 'frontCollider']) {
scene.getMeshByName(name).checkCollisions = true;
}
if (canvas) camera.attachControl(canvas, true);
scene.activeCamera = camera;
return camera;
}
// ---- A tiny stand-in for Havok ----
// Havok's WebAssembly module has to be downloaded, which this sandboxed preview cannot do, so
// these pages simulate with a few lines of their own: axis-aligned boxes that fall, bounce,
// slide with friction, stack and sleep (no rotation), stepped at a fixed 1/60 s like
// new BABYLON.HavokPlugin(false, havok). Comments name the Havok call each part stands for.
class MiniWorld {
constructor(gravity = -9.81) {
this.gravity = gravity;
this.bodies = [];
this.contacts = new Set(); // pairs touching in the last step
this.onCollision = null; // ({ a, b, impulse }) on first contact
this.onTrigger = null; // ({ trigger, body }) when a body enters
}
// Like new PhysicsAggregate(mesh, PhysicsShapeType.BOX, { mass, restitution, friction })
addBox(mesh, { mass = 0, restitution = 0.2, friction = 0.6, isTrigger = false, half = null, center = null } = {}) {
mesh.computeWorldMatrix(true);
const box = mesh.getBoundingInfo().boundingBox;
const body = { mesh, mass, restitution, friction, isTrigger, sleeping: false, still: 0,
half: half ?? box.extendSizeWorld.clone(), center: (center ?? box.centerWorld).clone(),
velocity: BABYLON.Vector3.Zero() };
body.offset = mesh.getAbsolutePosition().subtract(body.center);
this.bodies.push(body);
return body;
}
// A static collider with no mesh of its own, like one child shape of a PhysicsShapeContainer
addStaticBox(center, half) {
const body = { mesh: { uniqueId: `static${this.bodies.length}`, parent: true }, mass: 0, restitution: 0.2,
friction: 0.6, isTrigger: false, sleeping: false, half, center, velocity: BABYLON.Vector3.Zero() };
this.bodies.push(body);
return body;
}
step(dt = 1 / 60) {
for (const b of this.bodies) { // integrate: gravity, then velocity
if (!b.mass || b.sleeping) continue;
b.velocity.y += this.gravity * dt;
b.center.addInPlace(b.velocity.scale(dt));
}
const touching = new Set();
for (let iteration = 0; iteration < 6; iteration++) { // relax the contacts a few times
for (let i = 0; i < this.bodies.length; i++) for (let j = i + 1; j < this.bodies.length; j++) {
const pair = this.resolve(this.bodies[i], this.bodies[j], iteration === 0);
if (pair) touching.add(pair);
}
}
this.contacts = touching;
for (const b of this.bodies) { // sleep bodies that have come to rest
if (!b.mass) continue;
b.still = b.velocity.length() < 0.05 ? b.still + 1 : 0;
if (b.still > 20) { b.sleeping = true; b.velocity.setAll(0); }
if (!b.mesh.parent) b.mesh.position.copyFrom(b.center.add(b.offset));
}
}
resolve(a, b, firstPass) {
if ((!a.mass || a.sleeping) && (!b.mass || b.sleeping)) return null;
const d = a.center.subtract(b.center);
const ox = a.half.x + b.half.x - Math.abs(d.x), oy = a.half.y + b.half.y - Math.abs(d.y),
oz = a.half.z + b.half.z - Math.abs(d.z);
if (ox <= 0 || oy <= 0 || oz <= 0) return null; // no overlap on some axis: no contact
const key = a.mesh.uniqueId + ':' + b.mesh.uniqueId;
if (a.isTrigger || b.isTrigger) { // triggers report, never push
if (firstPass && !this.contacts.has(key) && this.onTrigger) {
this.onTrigger(a.isTrigger ? { trigger: a, body: b } : { trigger: b, body: a });
}
return key;
}
const n = new BABYLON.Vector3(); // push apart along the shallowest axis
const depth = Math.min(ox, oy, oz);
if (depth === oy) n.y = Math.sign(d.y) || 1; else if (depth === ox) n.x = Math.sign(d.x) || 1; else n.z = Math.sign(d.z) || 1;
const ia = a.mass && !a.sleeping ? 1 / a.mass : 0, ib = b.mass && !b.sleeping ? 1 / b.mass : 0;
a.center.addInPlace(n.scale(depth * ia / (ia + ib)));
b.center.subtractInPlace(n.scale(depth * ib / (ia + ib)));
const vn = BABYLON.Vector3.Dot(a.velocity.subtract(b.velocity), n);
if (vn < 0) { // approaching: bounce with restitution
const e = vn < -0.5 ? Math.min(a.restitution, b.restitution) : 0;
const impulse = -(1 + e) * vn / (ia + ib);
a.velocity.addInPlace(n.scale(impulse * ia));
b.velocity.subtractInPlace(n.scale(impulse * ib));
const mu = Math.sqrt(a.friction * b.friction); // friction slows the sliding part
for (const body of [a, b]) {
const tangent = body.velocity.subtract(n.scale(BABYLON.Vector3.Dot(body.velocity, n)));
body.velocity.subtractInPlace(tangent.scale(Math.min(mu * 0.5, 1)));
}
for (const body of [a, b]) { // a hard hit wakes a sleeping body
if (impulse > 0.5 && body.mass && body.sleeping) { body.sleeping = false; body.still = 0; }
}
if (firstPass && !this.contacts.has(key) && this.onCollision) this.onCollision({ a, b, impulse });
}
return key;
}
// Like physicsEngine.raycastToRef(from, to, result): the nearest box a segment enters
raycast(from, to) {
const ray = BABYLON.Ray.CreateNewFromTo(from, to);
let best = null;
for (const body of this.bodies) {
if (body.isTrigger) continue;
const min = body.center.subtract(body.half), max = body.center.add(body.half);
if (!ray.intersectsBoxMinMax(min, max)) continue;
let distance = 0; // slab test: where the ray enters the box
for (const axis of ['x', 'y', 'z']) {
const inv = 1 / (ray.direction[axis] || 1e-9);
const t1 = (min[axis] - ray.origin[axis]) * inv, t2 = (max[axis] - ray.origin[axis]) * inv;
distance = Math.max(distance, Math.min(t1, t2));
}
if (distance <= ray.length && (!best || distance < best.distance)) {
best = { body, distance, point: from.add(ray.direction.scale(distance)) };
}
}
return best;
}
}
// ---- end of the stand-in ----
function createDisplayTable(scene, world, x, z) { // a top and four legs, one render mesh
const parts = [[1.2, 0.05, 0.8, 0, 0.725, 0]]; // width, height, depth, offset
for (const [lx, lz] of [[-0.55, -0.35], [0.55, -0.35], [-0.55, 0.35], [0.55, 0.35]]) parts.push([0.06, 0.7, 0.06, lx, 0.35, lz]);
const meshes = parts.map(([w, h, d, px, py, pz]) => {
const part = BABYLON.MeshBuilder.CreateBox('part', { width: w, height: h, depth: d }, scene);
part.position.set(x + px, py, z + pz);
return part;
});
// one static collider per part, like the child shapes of a PhysicsShapeContainer
const colliders = meshes.map((part) => world.addBox(part, { mass: 0 }));
const table = BABYLON.Mesh.MergeMeshes(meshes, true);
table.name = 'displayTable';
table.material = paint(scene, 'tableWood', '#8d6e4f');
colliders.forEach((body) => { body.mesh = table; }); // the merged mesh stands for them all
return { table, colliders };
}
function dropBooks(scene, world, shelved, x, z) { // copies of the shelved books, tipped in
return shelved.map((original, i) => {
const book = original.clone(original.name + 'Copy'); // keeps metadata and material
book.parent = null;
book.position.set(x - 0.25 + (i % 3) * 0.22, 1 + i * 0.2, z - 0.1 + (i % 2) * 0.2);
if (i % 3 !== 1) book.rotation.z = Math.PI / 2; // most land flat, some stand up
if (i % 2) book.rotation.y = Math.PI / 2;
book.computeWorldMatrix(true);
const pages = book.metadata.pages;
world.addBox(book, { mass: pages * 0.002, friction: 0.6, restitution: 0.1 }); // 2 g a page
return book;
});
}
function fillShelves(scene, bookcase, shelves = [0, 1, 3]) {
const stock = BABYLON.MeshBuilder.CreateBox(`${bookcase.name}Stock`, { depth: 0.2 }, scene);
Object.assign(stock, { parent: bookcase, material: paint(scene, 'stock', '#ffffff') });
let seed = 7; // a repeatable pseudo-random sequence
const random = () => (seed = (seed * 16807) % 2147483647) / 2147483647;
const matrices = [], colors = [];
for (const shelf of shelves) {
for (let x = -1.44; x < 1.36;) { // left to right along the board
const width = 0.025 + 0.045 * random(), height = 0.22 + 0.1 * random();
const at = new BABYLON.Vector3(x + width / 2, 0.12 + shelf * 0.5 + height / 2, -0.02);
matrices.push(...BABYLON.Matrix.Compose(new BABYLON.Vector3(width, height, 1),
BABYLON.Quaternion.Identity(), at).m); // scale the unit box, then place it
const color = BABYLON.Color3.FromHexString(BOOKS[Math.floor(random() * 6)].color);
colors.push(...color.scale(0.6 + 0.5 * random()).asArray(), 1); // palette, shaded
x += width + 0.004;
}
}
stock.thinInstanceSetBuffer('matrix', new Float32Array(matrices), 16); // one draw call
stock.thinInstanceSetBuffer('color', new Float32Array(colors), 4); // per-book tint
stock.freezeWorldMatrix(); // the stock never moves
return stock;
}
class SoldOutPlugin extends BABYLON.MaterialPluginBase {
constructor(material) { super(material, 'SoldOut', 200, { SOLD_OUT: false }); this._enable(true); }
prepareDefines(defines) { defines.SOLD_OUT = true; }
getClassName() { return 'SoldOutPlugin'; }
isCompatible() { return true; }
getCustomCode(shaderType, language) {
if (shaderType !== 'fragment') return null;
const code = language === BABYLON.ShaderLanguage.WGSL
? `{ let luma = dot(fragmentOutputs.color.rgb, vec3f(0.299, 0.587, 0.114));
fragmentOutputs.color = vec4f(mix(vec3f(luma), vec3f(0.93), 0.35), fragmentOutputs.color.a); }`
: `{ float luma = dot(gl_FragColor.rgb, vec3(0.299, 0.587, 0.114));
gl_FragColor.rgb = mix(vec3(luma), vec3(0.93), 0.35); }`;
return { CUSTOM_FRAGMENT_MAIN_END: `#ifdef SOLD_OUT\n${code}\n#endif` };
}
}
// ---- openStore: the whole bookstore, assembled step by step (stage limits how far it goes) ----
async function openStore(engine, canvas, stage = 7) {
const scene = createScene(engine);
createRoom(scene); // 1: room, walls, sidewalk, cases
const camera = createWalkCamera(scene, canvas); // before the wall replaces its collider
const wall = createFrontWall(scene);
wall.checkCollisions = true;
scene.getMeshByName('frontCollider')?.dispose();
const sidewalk = BABYLON.MeshBuilder.CreateGround('sidewalk', { width: ROOM.width, height: 3 }, scene);
Object.assign(sidewalk, { material: paint(scene, 'paving', '#9e9e9e'), checkCollisions: true });
sidewalk.position.z = -ROOM.depth / 2 - 1.5; // 3 m of pavement outside the front
const cases = [['bookcaseLeft', -1.8], ['bookcaseRight', 1.8]].map(([name, x]) => createBookcase(scene, name, x));
cases.forEach((bookcase) => { bookcase.checkCollisions = true; });
const store = { scene, camera, cases };
if (stage < 2) return store;
const books = placeBooks(scene, cases[0]); // 2: spine widths from page counts
books.forEach((book) => book.metadata.inStock || new SoldOutPlugin(book.material)); // the catalog's flags
fillShelves(scene, cases[0]); // stock around the six
fillShelves(scene, cases[1], [0, 1, 2, 3]);
const world = new MiniWorld(); // new arrivals tipped onto a table in the window
world.addStaticBox(new BABYLON.Vector3(0, -0.05, 0), new BABYLON.Vector3(4, 0.05, 3));
const { table } = createDisplayTable(scene, world, -1.4, -2.3);
table.checkCollisions = true;
dropBooks(scene, world, books, -1.4, -2.3);
let steps = 0;
scene.onBeforeRenderObservable.add(() => { if (steps++ < 150) world.step(1 / 60); }); // then it sleeps
Object.assign(store, { books, world });
camera.position.set(2.3, 1.6, -5); // 3: on the sidewalk, facing the door
camera.setTarget(new BABYLON.Vector3(2.3, 1.6, 0));
if (stage < 4) return store;
const details = createDetailsPanel(scene); // 4: a tap opens the panel
const { select } = enableBookPicking(scene, books, details.show);
const cards = createShelfCards(scene, cases[0], books, select); // so does a card
Object.assign(store, { details, select, cards });
if (stage < 5) return store;
store.lights = lightRoom(scene); // 5: everything above casts
scene.getMeshByName('ceiling').layerMask = camera.layerMask; // walkers see a ceiling
useEnvironment(scene);
if (stage < 6) return store;
store.dust = addDust(scene); // 6: motes, and sound after the first click
store.ambience = await createAmbience(scene, camera).catch(() => null);
if (stage < 7) return store;
const look = createStorefrontLook(scene, camera); // 7: sign, glow, color grade
details.layer.applyPostProcess = false; // draw the GUI after the color grade
let outside = true;
scene.onBeforeRenderObservable.add(() => { // the look follows the visitor
outside = camera.position.z < -ROOM.depth / 2; // in front of the front wall
look.pipeline.imageProcessing.exposure = outside ? 1 : 1.8; // eyes adapt indoors
});
look.sheen.onApply = (effect) => effect.setFloat('strength', outside ? 0.15 : 0);
store.look = look;
return store;
}
const canvas = document.getElementById('view');
const engine = new BABYLON.Engine(canvas, true, {}, true);
openStore(engine, canvas, 3).then(({ scene, camera }) => {
camera.detachControl();
const overview = new BABYLON.ArcRotateCamera('overview', -2.1, 0.75, 13, new BABYLON.Vector3(0.3, 0.5, -1), scene);
overview.attachControl(canvas, true);
scene.activeCamera = overview; // watch the walker from above
const body = BABYLON.MeshBuilder.CreateSphere('body', { diameterX: 0.6, diameterY: 1.6, diameterZ: 0.6 }, scene);
body.material = paint(scene, 'bodyMat', '#2a9d8f');
body.isPickable = false;
const trail = [];
let line = null;
const info = document.getElementById('info');
const results = [];
const WALKS = [['door', 2.3], ['window', -1.4]];
let walk = 0, frames = 0;
const start = () => {
const [, x] = WALKS[walk];
camera.position.set(x, 1.6, -5); // on the sidewalk, facing the shop
camera.setTarget(new BABYLON.Vector3(x, 1.6, 0));
trail.length = 0;
frames = 0;
};
start();
scene.onBeforeRenderObservable.add(() => {
camera.cameraDirection.set(0, 0, 0.025); // "forward" held down: 2.5 cm a frame
camera.update(); // the move passes through the collisions
body.position.copyFrom(camera.position).y -= 0.8;
if (frames++ % 5 === 0) {
trail.push(new BABYLON.Vector3(camera.position.x, 0.03, camera.position.z));
line?.dispose();
if (trail.length > 1) {
line = BABYLON.MeshBuilder.CreateLines('trail', { points: trail }, scene);
line.color = BABYLON.Color3.FromHexString('#b5452f');
}
}
if (frames === 300) { // five seconds per walk
const at = camera.position.asArray().map((v) => v.toFixed(2)).join(', ');
results[walk] = `toward the ${WALKS[walk][0]}: stopped at (${at})`;
info.textContent = results.join('\n');
walk = (walk + 1) % WALKS.length;
start();
}
});
engine.runRenderLoop(() => scene.render());
});
addEventListener('resize', () => engine.resize());
</script>