ecsy
ECSY (pronounced as "eck-see") is an highly experimental Entity Component System framework implemented in javascript, aiming to be lightweight, easy to use and with good performance.
For detailed information on the architecture and API please visit the documentation page
- discourse forum: https://discourse.mozilla.org/c/mixed-reality/ecsy
- discord: https://discord.gg/cFnrQ2v
Features
- Framework agnostic
- Focused on providing a simple but yet efficient API
- Designed to avoid garbage collection as possible
- Systems, entities and components are scoped in a
worldinstance - Multiple queries per system
- Reactive support:
- Support for reactive behaviour on systems (React to changes on entities and components)
- System can query mutable or immutable components
- Predictable:
- Systems will run on the order they were registered or based on the priority defined when registering them
- Reactive events will not generate a random callback when emited but queued and be processed in order
- Modern Javascript: ES6, classes, modules,...
- Pool for components and entities
Goals
Our goal is for ECSY to be a lightweight, simple, and performant ECS library that can be easily extended and encoruages open source collaboration.
ECSY will not ship with features that bind it to a rendering engine or framework. Instead, we encourage the community to build framework specific projects like ecsy-three, ecsy-babylon, and ecsy-two.
ECSY does not adhere strictly to "pure ECS design". We focus on APIs that push users towards good ECS design like putting their logic in systems and data in components. However, we will sometimes break the rules for API ergonomics, performance in a JS context, or integration with non-ECS frameworks.
ECSY is designed for a community driven ecosystem. We encourage users to come up with modular components and systems that can be composed into larger games, apps, and engines.
Examples
- Ball example:
- 2D Canvas https://ecsyjs.github.io/ecsy/examples/canvas
- Factory pattern with
Notoperator: https://ecsyjs.github.io/ecsy/examples/factory - System state component example: https://ecsyjs.github.io/ecsy/examples/systemstatecomponents
Usage
Installing the package via npm:
npm install --save ecsy<!DOCTYPE html>
<html lang="en">
<head>
<title>Hello!</title>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>
html, body: {
margin: 0;
padding: 0;
}
</style>
<script type="module">
import { World, System, Component, TagComponent, Types } from "https://ecsyjs.github.io/ecsy/build/ecsy.module.js";
const NUM_ELEMENTS = 50;
const SPEED_MULTIPLIER = 0.3;
const SHAPE_SIZE = 50;
const SHAPE_HALF_SIZE = SHAPE_SIZE / 2;
// Initialize canvas
let canvas = document.querySelector("canvas");
let canvasWidth = canvas.width = window.innerWidth;
let canvasHeight = canvas.height = window.innerHeight;
let ctx = canvas.getContext("2d");
//----------------------
// Components
//----------------------
// Velocity component
class Velocity extends Component {}
Velocity.schema = {
x: { type: Types.Number },
y: { type: Types.Number }
};
// Position component
class Position extends Component {}
Position.schema = {
x: { type: Types.Number },
y: { type: Types.Number }
};
// Shape component
class Shape extends Component {}
Shape.schema = {
primitive: { type: Types.String, default: 'box' }
};
// Renderable component
class Renderable extends TagComponent {}
//----------------------
// Systems
//----------------------
// MovableSystem
class MovableSystem extends System {
// This method will get called on every frame by default
execute(delta, time) {
// Iterate through all the entities on the query
this.queries.moving.results.forEach(entity => {
var velocity = entity.getComponent(Velocity);
var position = entity.getMutableComponent(Position);
position.x += velocity.x * delta;
position.y += velocity.y * delta;
if (position.x > canvasWidth + SHAPE_HALF_SIZE) position.x = - SHAPE_HALF_SIZE;
if (position.x < - SHAPE_HALF_SIZE) position.x = canvasWidth + SHAPE_HALF_SIZE;
if (position.y > canvasHeight + SHAPE_HALF_SIZE) position.y = - SHAPE_HALF_SIZE;
if (position.y < - SHAPE_HALF_SIZE) position.y = canvasHeight + SHAPE_HALF_SIZE;
});
}
}
// Define a query of entities that have "Velocity" and "Position" components
MovableSystem.queries = {
moving: {
components: [Velocity, Position]
}
}
// RendererSystem
class RendererSystem extends System {
// This method will get called on every frame by default
execute(delta, time) {
ctx.fillStyle = "#d4d4d4";
ctx.fillRect(0, 0, canvasWidth, canvasHeight);
// Iterate through all the entities on the query
this.queries.renderables.results.forEach(entity => {
var shape = entity.getComponent(Shape);
var position = entity.getComponent(Position);
if (shape.primitive === 'box') {
this.drawBox(position);
} else {
this.drawCircle(position);
}
});
}
drawCircle(position) {
ctx.beginPath();
ctx.arc(position.x, position.y, SHAPE_HALF_SIZE, 0, 2 * Math.PI, false);
ctx.fillStyle= "#39c495";
ctx.fill();
ctx.lineWidth = 2;
ctx.strokeStyle = "#0b845b";
ctx.stroke();
}
drawBox(position) {
ctx.beginPath();
ctx.rect(position.x - SHAPE_HALF_SIZE, position.y - SHAPE_HALF_SIZE, SHAPE_SIZE, SHAPE_SIZE);
ctx.fillStyle= "#e2736e";
ctx.fill();
ctx.lineWidth = 2;
ctx.strokeStyle = "#b74843";
ctx.stroke();
}
}
// Define a query of entities that have "Renderable" and "Shape" components
RendererSystem.queries = {
renderables: { components: [Renderable, Shape] }
}
// Create world and register the components and systems on it
var world = new World();
world
.registerComponent(Velocity)
.registerComponent(Position)
.registerComponent(Shape)
.registerComponent(Renderable)
.registerSystem(MovableSystem)
.registerSystem(RendererSystem);
// Some helper functions when creating the components
function getRandomVelocity() {
return {
x: SPEED_MULTIPLIER * (2 * Math.random() - 1),
y: SPEED_MULTIPLIER * (2 * Math.random() - 1)
};
}
function getRandomPosition() {
return {
x: Math.random() * canvasWidth,
y: Math.random() * canvasHeight
};
}
function getRandomShape() {
return {
primitive: Math.random() >= 0.5 ? 'circle' : 'box'
};
}
for (let i = 0; i < NUM_ELEMENTS; i++) {
world
.createEntity()
.addComponent(Velocity, getRandomVelocity())
.addComponent(Shape, getRandomShape())
.addComponent(Position, getRandomPosition())
.addComponent(Renderable)
}
// Run!
function run() {
// Compute delta and elapsed time
var time = performance.now();
var delta = time - lastTime;
// Run all the systems
world.execute(delta, time);
lastTime = time;
requestAnimationFrame(run);
}
var lastTime = performance.now();
run();
</script>
</head>
<body>
<canvas width="500" height="500"></canvas>
</body>
</html>You can also include the hosted javascript directly on your HTML:
<!-- Using UMD (It will expose a global ECSY namespace) -->
<script src="https://ecsyjs.github.io/ecsy/build/ecsy.js"></script>
<!-- Using ES6 modules -->
<script src="https://ecsyjs.github.io/ecsy/build/ecsy.module.js"></script>