Babylon.js multiplayer

Babylon.js multiplayer, hosted

Babylon's render loop and observables map naturally onto the SDK's events. Remote meshes are created on members, updated on peer, and your HUD reacts to state.watch. Nothing runs on a server you own.

A complete Babylon.js integration

import { Multiplayer } from 'https://multiplayerapi.com/sdk/mp.esm.min.js';

const mp = new Multiplayer({ key: 'mp_pk_...' });
await mp.login();
const room = await mp.quickmatch({ mode: 'coop', max_players: 6 });

const avatars = {};
room.on('peer', (p, from) => {
  const a = avatars[from] ??= BABYLON.MeshBuilder.CreateCapsule('p_' + from, { height: 1.8 }, scene);
  a.metadata = { target: new BABYLON.Vector3(p.x, p.y, p.z), yaw: p.yaw };
});
room.on('members', (list) => {
  const alive = new Set(list.map((m) => m.account_id));
  for (const id in avatars) if (!alive.has(id)) { avatars[id].dispose(); delete avatars[id]; }
});

scene.onBeforeRenderObservable.add(() => {
  for (const a of Object.values(avatars)) if (a.metadata) {
    a.position = BABYLON.Vector3.Lerp(a.position, a.metadata.target, 0.25);
    a.rotation.y = a.metadata.yaw;
  }
});

setInterval(() => {
  const p = player.position;
  room.send({ x: p.x, y: p.y, z: p.z, yaw: player.rotation.y });
}, 50);

// Co-op world: everyone may write, at a bounded rate
room.inc('world.resources.wood', -10);
room.state.watch('world.resources.*', (v, path) => ui.update(path, v));

What goes where

• Use preset coop for shared worlds: rules such as "world.**": {"write":"any","rate":10} let everyone build while capping spam.
• For Babylon XR, send head and hand poses on the direct channel exactly like the player transform.

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