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whoppingchill on 09/12/13

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4 Balls Collision II

/ Published in: JavaScript

Simulation of the collision of 4 balls using limejs and box2d.

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//set main namespace
goog.provide('collisionLime');
//get requirements
goog.require('lime.Director');
goog.require('lime.Scene');
goog.require('lime.Layer');
goog.require('lime.Circle');
goog.require('box2d.World');
goog.require('box2d.Body');
goog.require('box2d.BodyDef');
goog.require('box2d.CircleDef');
goog.require('box2d.Vec2');

// entrypoint
collisionLime.start = function(){
	// colours
	var red = 'rgb(155, 0, 0)';
	var green = 'rgb(0, 155, 0)';
	var blue = 'rgb(0, 0, 155)';
	var yellow = 'rgb(155, 155, 0)';
	
	// director
	var director = new lime.Director(document.body, 600, 600);
	var scene = new lime.Scene();
	var layer = new lime.Layer; // photoshop layer; append child
	// layer.setPosition(300, 300);
	scene.appendChild(layer);
	director.replaceScene(scene);
	
	// box2d
	var gravity = new box2d.Vec2(0, 0); // no gravity in x and y direction
	var bounds = new box2d.AABB();
	bounds.minVertex.Set(0, 0);
	bounds.maxVertex.Set(600, 600);
	var world = new box2d.World(bounds, gravity, false);
	
	// create a circle
	function createCircle(radius, x, y, color, layer) {
		// limejs
		var circle = (new lime.Circle)
			.setFill(color)
			.setSize(radius * 2, radius * 2);
		layer.appendChild(circle);
		
		// box2d
		var bodyDef = new box2d.BodyDef;
		bodyDef.type = box2d.Body.b2_dynamicBody; // can move and rotate
		bodyDef.position.Set(x, y);
		bodyDef.awake = true;
		bodyDef.angularDamping = 0; // friction without contact - 0.001
		bodyDef.userData = circle;
		
		var circleDef = new box2d.CircleDef;
		circleDef.radius = radius;
		circleDef.density = 5; // kg/m^2
		circleDef.friction = 0.5; // 0 to 1, 0 means no friction
		circleDef.restitution = 0.5; // 0 to 1, 0 means won't bounce
		bodyDef.AddShape(circleDef);
		
		var body = world.CreateBody(bodyDef);
		return body;
	}
	
	function createRect(x, y, width, height, rotation, layer) {
		// limejs
		var rect = (new lime.Sprite)
			.setFill('#ccc')
			.setSize(width, height);
		layer.appendChild(rect);
		
		// box2d
		var bodyDef = new box2d.BodyDef;
		bodyDef.type = box2d.Body.b2_staticBody;
		bodyDef.position.Set(x, y);
		bodyDef.rotation = -rotation / 180 * Math.PI;
		bodyDef.userData = rect;
		
		var rectDef = new box2d.BoxDef;
		rectDef.density = 0; // static object, so not required
		rectDef.friction = 1;
		rectDef.restitution = 0.9;
		rectDef.extents.Set(width / 2, height / 2);
		bodyDef.AddShape(rectDef);
		
		var body = world.CreateBody(bodyDef);
		return body;
	}
	
	function autoMove(shape, vel_x, vel_y) {
		shape._body.SetLinearVelocity(new box2d.Vec2(vel_x, vel_y));
	}
	
	function updateBody(body){
		var rot = body.GetRotation();
		var shape = body.GetUserData();
		shape.setRotation(-rot / Math.PI * 180);
		shape.setPosition(body.GetCenterPosition().x, body.GetCenterPosition().y);
	}
	
	var circleP1 = createCircle(30, 50, 300, red, layer),
	    circleP2 = createCircle(30, 300, 50, green, layer),
	    circleP3 = createCircle(30, 550, 300, blue, layer),
	    circleP4 = createCircle(30, 300, 550, yellow, layer),
            rectLeft = createRect(10, 300, 20, 600, 0, layer),
	    rectTop = createRect(300, 10, 600, 20, 0, layer),
	    rectRight = createRect(590, 300, 20, 600, 0, layer),
	    rectBottom = createRect(300, 590, 600, 20, 0, layer);
	
	var vel_x = 50, vel_y = 50;
	circleP1.SetLinearVelocity(new box2d.Vec2(vel_x, 0));
	circleP2.SetLinearVelocity(new box2d.Vec2(0, vel_y));
	circleP3.SetLinearVelocity(new box2d.Vec2(-vel_x, 0));
	circleP4.SetLinearVelocity(new box2d.Vec2(0 , -vel_y));
	
	lime.scheduleManager.schedule(function(dt) {
        world.Step(dt / 60, 6, 2); // 60Hz, velocityIt, positionIt
        
	updateBody(circleP1);
        updateBody(circleP2);
	updateBody(circleP3);
        updateBody(circleP4);
	updateBody(rectLeft);
	updateBody(rectTop);
	updateBody(rectRight);
	updateBody(rectBottom);
    },this);
}

//this is required for outside access after code is compiled in ADVANCED_COMPILATIONS mode
goog.exportSymbol('collisionLime.start', collisionLime.start);

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