dartemis

A Dart port of the Entity System Framework Artemis.

The original has been written in Java by Arni Arent and Tiago Costa and can be found here: http://gamadu.com/artemis with the source available here: https://code.google.com/p/artemis-framework/

Ports for other languages are also available:

  • C#: https://github.com/thelinuxlich/artemis_CSharp
  • Python: https://github.com/kernhanda/PyArtemis

Some useful links about what an Entity System/Entity Component System is:

  • http://piemaster.net/2011/07/entity-component-artemis/
  • http://t-machine.org/index.php/2007/09/03/entity-systems-are-the-future-of-mmog-development-part-1/

Getting started

1\. Add dartemis to your project by adding it to your pubspec.yaml 2\. Import it in your project:

import 'package:dartemis/dartemis.dart';

3\. Create a world:

World world = new World();

4\. Create entities, add components to them and finally add those entities to the world. Entities with different components will be processed by different systems:

Entity entity  = world.createEntity();
entity.addComponent(new Position(world, 0, 0));
entity.addComponent(new Velocity(world, 1, 1));
entity.addToWorld();

A Component is a pretty simple structure and should not contain any logic:

class Position extends Component {
    num x, y;

    Position._();
    factory Position(num x, num y) {
        Position position = new Component(Position, _constructor);
        position.x = x;
        position.y = y;
        return position;
    }
    static Position _constructor() => new Position._();
}

By using a factory constructor and calling the factory constructor in Component the system is able to reuse destroyed components and no garbage collection will occur as long as the world exists. For more information about why this is done you might want to read this article: Free Lists For Predictable Game Performance

5\. Define a systems that should process your entities. The Aspect defines which components an entity needs to have in order to be processed by the system:

class MovementSystem extends EntityProcessingSystem {
    ComponentMapper<Position> positionMapper;
    ComponentMapper<Velocity> velocityMapper;
  
    MovementSystem() : super(Aspect.getAspectForAllOf([Position, Velocity]));
  
    void initialize() {
      positionMapper = new ComponentMapper<Position>(Position, world);
      velocityMapper = new ComponentMapper<Velocity>(Velocity, world);
    }
  
    void processEntity(Entity entity) {
      Position position = positionMapper.get(entity);
      Velocity vel = velocityMapper.get(entity);  
      position.x += vel.x;
      position.y += vel.y;
    }
}

6\. Add your system to the world:

world.addSystem(new MovementSystem());

7\. Initialize the world:

world.initialize();

8\. In your game loop you then process your systems:

world.process();

If your game logic requires a delta you can set it by calling:

world.delta = delta;

Documentation

API

Reference Manual

Example Games using dartemis

darteroids

An very simple example included in the example folder of dartemis: Source Code Playable version

GitHub Space Off

A game originally created for the GitHub Game Off 2012 Source Code Playable version

Libraries

dartemis