Impact Box2D Sugar

This plugin aims to make Box2D development with ImpactJS as easy as possible.

Installation

Copy the contents of this repo into lib/plugins/joncom/box2d/.

Example Game

ig.module('game.main')
.requires(
    'plugins.joncom.box2d.game',
    'plugins.joncom.box2d.debug' // Optional, draws body shapes.
)
.defines(function(){
    MyGame = ig.Game.extend({
        /* your game code here */
    });
    ig.main( '#canvas', MyGame, 60, 320, 240, 2 );
});

Example Entity

ig.module('game.entities.player')
.requires('plugins.joncom.box2d.entity')
.defines(function(){
    EntityPlayer = ig.Entity.extend({
        /* your entity code here */
    });
});

New Entity Properties

.isBullet

Setting true enables continuous collision. This prevents fast moving entities from "tunneling" through walls and other entities, but requires more CPU. Default is false.

.isFixedRotation

Setting true prevents body from rotating. Default is false.

.isSensor

Setting true prevents the entity from physically interacting with other entities or the world. .touches still works. .check and .collideWith still fire. Default is false.

.mass

Mass of entity in kilograms. Calculated automatically during init if null. Default is null.

.density

Used to calculate mass during init if mass is not null. Mass is recalculated if this value changes. Default is 1.

.maySleep

Allow or disallow the entity to sleep when inactive. When sleeping Box2D does not calculate physics for this entity, thus saving CPU. Default is false.

Restored Entity Properties

######.pos######

// Shift the entity to the right 100 pixels.
entity.pos.x += 100;

######.vel######

// Make the entity jump upward.
entity.vel.x -= 300;

######.standing######

if(entity.standing) {
	entity.jump();
}

######.touches######

if(enemy.touches(player)) {
    player.kill();
}

######.gravityFactor######

EntityPlayer = ig.Entity.extend({
    // Increases the effect gravity has on the individual entity.
    gravityFactor: 3,
});

######.last######

/* your-entity.js */
update: function () {
    if(this.last.x !== this.pos.x) {
        console.log("Entity moved horizontally.");
    }

    // Make sure you get your this.last reading
    // before calling this.parent()...
    this.parent();
}

######.friction######

// Box2D does not distinguish between X and Y
// frictions. Therefore set friction like this:
entity.friction.x = 3;
// or like this:
entity.friction.y = 3;
// They both do the exact same thing.

######.maxVel######

// Cap the vertical speed of an entity.
entity.maxVel.y = 300;

######.bounciness######

EntityExample = ig.Entity.extend({
    bounciness: 1 // Full bounce.
}
// You can change the value at any time.
entity.bounciness = 0.5;

######.type, .checkAgainst, .check, and .collideWith######

EntityPlayer = ig.Entity.extend({
    type: ig.Entity.TYPE.A,
    checkAgainst: ig.Entity.TYPE.B,
    check: function(entity) {
        console.log('Player is touching ' + entity.name);
    },
    collideWidth: function(entity, axis) {
        console.log('Player just collided with ' +
            entity.name + ' on the ' + axis + ' axis.');
    }
});

FAQ

Q: What version of Box2D is this? A: Box2D 2.1a via Box2DWeb.

Q: Are Weltmeister slope tiles supported? A: Yes. (Thanks Collin Hover)

Q: Where is some good documentation on this version of Box2D? A: Here.