artbox

A physics and game entity engine for Android.

Introduction

The artbox engine is the integration of jbox2d (used to handle the physics interactions) and an overarching artemis framework. The artemis framework defines three types of objects:

Components hold data such as position or velocity or an bitmap image.
Entities are bags that hold Components and encapsulate the notion of a game object.
Systems perform operations on Entities that have particular Components - this is what evolves the game state.

For example, a player Entity may have three Components: PositionComponent, VelocityComponent, and BitmapComponent. A PositionUpdateSystem may define itself to operate on Entities with a PositionComponent and a VelocityComponent. With some pseudocode, this operation could look like this:

public void process(Entity e) {
    PositionComponent position = e.getPositionComponent();
    VelocityComponent velocity = e.getVelocityComponent();
    
    position.setX(position.getX() + timeStep * velocity.getVx());
    position.setY(position.getY() + timeStep * velocity.getVy());
}

This process method is then performed on every Entity with a PositionComponent and VelocityComponent and in this way, the positions for each Entity is evolved according to clearly defined logical rules.

A key point here is that the PositionUpdateSystem does not care that our player Entity has a BitmapComponent. Data that is not within the scope of the System is not operated on. This allows us to define other Systems that operate on different sets of Components with full knowledge of what types of Systems are using the same data. For instance, a BitmapRenderSystem could operate on Entities with a PositionComponent and BitmapComponent by drawing the bitmap at the position given by PositionComponent.

Features

Fully integrated artemis and jbox2d frameworks to provide quick and easy development of 2D Android games.
API for injecting new Components, Entities, and Systems into the base engine to define new objects and behaviors.
JSON-backed Entities allow for designing game objects without touching the source code.

Installing

You can either download the .jar (when it is released), or import this project as a library project in Eclipse.

License

Acknowledgments

This project draws heavily from the Artemis Component Entity System framework for maintaining and processing game state, and the Java port of box2d, a 2D physics engine.

Contributing

Please fork this repository and contribute back using pull requests. Features can be requested using issues. All code, comments, and critiques are greatly appreciated.

whoshuu / artbox