Elixr is a lightweight and flexible framework for building WebXR experiences. Built on top of the popular three.js library and integrated with the highly performant Rapier physics engine, Elixr aims to provide an easy-to-use and customizable solution for creating XR experiences on the web.

Table of contents

Key features | Installation | Usage | API | License

Key features

• 🚀 Easy-to-use WebXR scene setup: Intuitive APIs for setting up WebXR scenes.
• 🎮 Powerful ECS architecture: Efficient game logic with a flexible entity-component system.
• 🏗️ Rapier physics integration: Realistic physics simulations with the highly performant Rapier physics engine.
• 🕹️ Pre-built, customizable interaction systems: Easily add pre-built interaction systems like snap-turn and teleportation.
• 🌐 Compatibility with three.js plugins: Build on top of an established three.js ecosystem with compatibility for plugins.

Installation

To install and set up the library, run:

$ npm install elixr

Or if you prefer using Yarn:

$ yarn add elixr

Usage

To import elixr and set up your new world with a cube:

import { Core, GameObject, PrimitiveType, THREE, VRButton } from 'elixr';

// create a Core objects automatically sets up the base scene and the render loop
Core.init(document.getElementById('scene-container')).then((core) => {
    const cubeObject = new GameObject();
    cubeObject.addComponent(MeshRenderer, {
        meshRef: new THREE.Mesh(
            new THREE.BoxGeometry(1, 1, 1),
            new THREE.MeshStandardMaterial({ color: 0xff0000 }),
        ),
    });
    cubeObject.position.set(0, 1, -2);

    // add some lighting
    core.scene.add(new THREE.AmbientLight(0xffffff, 0.5));
    core.scene.add(new THREE.DirectionalLight(0xffffff, 1));

    // convert a button to the Enter VR button
    const vrButton = document.getElementById('vr-button');
    VRButton.convertToVRButton(vrButton, core.renderer);
});

Use ECS to add a spin behavior to that cube:

import { GameComponent, GameSystem } from 'elixr';

class Spin extends GameComponent {}

class SpinSystem extends GameSystem {
    // update(delta, time) is run every frame, define the game loop behavior here
    update(delta) {
        // query game objects as defined in SpinSystem.queries
        this.queryGameObjects('cubes').forEach((cubeObject) => {
            // GameObjects extends THREE.Object3D
            cubeObject.rotateY(Math.PI * delta);
        });
    }
}

SpinSystem.queries = {
    cubes: { components: [Spin] },
};

core.registerGameComponent(Spin);
core.registerGameSystem(SpinSystem);

// GameObjects also function as entities that can be queried in systems
cubeObject.addComponent(Spin);

Make the world and the cube have physics:

import { Core, GameObject, PrimitiveType, THREE, VRButton } from 'elixr';

// set gravity
core.physics.gravity.set(0, -9.8, 0);

// primitive objects come with rigidbodies and colliders
const cubeObject = GameObject.createPrimitive(PrimitiveType.Cube);
cubeObject.position.set(0, 10, -2);
const floor = GameObject.createPrimitive(PrimitiveType.Plane);
floor.position.set(0, 0, 0);

To implement naive joystick movement:

import { AXES, Vector3, XRGameSystem } from 'elixr';

const MAX_MOVEMENT_SPEED = 1;

export class JoystickMovementSystem extends XRGameSystem {
    update(delta, _time) {
        // "left" and "right" controllers are stored in core.controllers
        // they are only available after entering XR
        if (!this.core.controllers['left']) return;
        const gamepad = this.core.controllers['left'].gamepad;
        const xValue = gamepad.getAxis(AXES.XR_STANDARD.THUMBSTICK_X);
        const zValue = gamepad.getAxis(AXES.XR_STANDARD.THUMBSTICK_Y);
        // core.playerSpace is a THREE.Group that contains the camera and both controllers
        this.core.playerSpace.position.x += xValue * delta * MAX_MOVEMENT_SPEED;
        this.core.playerSpace.position.z += zValue * delta * MAX_MOVEMENT_SPEED;
    }
}

API

Please refer to elixrjs.io for full API documentation.

License

Apache-2.0 License © 2023 Felix Zhang