{"id":771,"date":"2009-01-13T09:00:29","date_gmt":"2009-01-13T08:00:29","guid":{"rendered":"http:\/\/www.matthijskamstra.nl\/blog\/?p=771"},"modified":"2009-01-12T13:06:44","modified_gmt":"2009-01-12T12:06:44","slug":"hello-box2d-part-3","status":"publish","type":"post","link":"https:\/\/www.matthijskamstra.nl\/blog\/2009\/01\/13\/hello-box2d-part-3\/","title":{"rendered":"Hello box2D – part 3"},"content":{"rendered":"

In my previous post<\/a> I update the “Hello world” for box2D so that you can see something visual happening.
\nYou can find the original here: AS3: Hello Box2D<\/a>.<\/p>\n

Today I will make it a little bit more attractive (remove trace).<\/p>\n

First we change some settings to make it more fun to watch at!<\/p>\n

The groundBodeDef<\/code> (strange name for something that is the ceiling) is moved more down so you can see where the bodyDef<\/code> is bouncing off.
\n[as]
\n\/\/groundBodyDef.position.Set(0.0, -10.0); \/\/ [mck]: old code
\ngroundBodyDef.position.Set(0.0, -9.0);
\n[\/as]<\/p>\n

The bodyDef<\/code> is moved to the center and dropped a little higher
\n[as]
\n\/\/bodyDef.position.Set(0.0, 4.0); \t\/\/ [mck]: old code
\nbodyDef.position.Set(10.0, 10.0);
\n[\/as]<\/p>\n

And the shapeDef<\/code> is bouncy so that you can see what box2D can do:
\n[as]
\nshapeDef.restitution = 0.8; \/\/ [mck]: extra new code
\n[\/as]<\/p>\n

And delete the trace:
\n[as]
\nvar position:b2Vec2 = body.GetPosition();
\nvar angle:Number = body.GetAngle();
\ntrace(position.x +’,’+ position.y +’,’+ angle);
\n[\/as]<\/p>\n

End result<\/h3>\n

The document class (HelloWorld.as<\/code>) will look like this:<\/p>\n

[as]
\npackage {<\/p>\n

\timport flash.display.*;
\n\timport flash.events.*;
\n\t\/\/ Box2D Classes used in this “Hello world”
\n\timport Box2D.Dynamics.*;
\n\timport Box2D.Collision.*;
\n\timport Box2D.Collision.Shapes.*;
\n\timport Box2D.Common.Math.*;<\/p>\n

\t\/\/ [SWF(width=”640″, height=”480″, backgroundColor=”#000000″, frameRate=”60″)]
\n\tpublic class HelloWorld extends Sprite {<\/p>\n

\t\tprivate var body:b2Body;
\n\t\tprivate var world:b2World;<\/p>\n

\t\t\/\/ constructor
\n\t\tpublic function HelloWorld() {
\n\t\t\ttrace( “HelloWorld.HelloWorld” );<\/p>\n

\t\t\t\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
\n\t\t\t\/\/ http:\/\/www.box2d.org\/wiki\/index.php?title=Manual\/AS3#Creating_a_World
\n\t\t\t\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
\n\t\t\t\/\/ Create world AABB
\n\t\t\tvar worldAABB:b2AABB = new b2AABB();
\n\t\t\tworldAABB.lowerBound.Set(-100.0, -100.0);
\n\t\t\tworldAABB.upperBound.Set(100.0, 100.0);<\/p>\n

\t\t\t\/\/ Define the gravity vector
\n\t\t\tvar gravity:b2Vec2 = new b2Vec2 (0.0, -10.0); <\/p>\n

\t\t\t\/\/ Allow bodies to sleep
\n\t\t\tvar doSleep:Boolean = true;<\/p>\n

\t\t\t\/\/ Construct a world object
\n\t\t\t\/\/ var world:b2World = new b2World(worldAABB, gravity, doSleep); \/\/ [mck]: old code
\n\t\t\tworld = new b2World(worldAABB, gravity, doSleep);<\/p>\n

\t\t\t\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
\n\t\t\t\/\/ http:\/\/www.box2d.org\/wiki\/index.php?title=Manual\/AS3#Creating_a_Ground_Box
\n\t\t\t\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
\n\t\t\tvar groundBodyDef:b2BodyDef = new b2BodyDef();
\n\t\t\tgroundBodyDef.position.Set(0.0, -10.0);<\/p>\n

\t\t\tvar groundBody:b2Body = world.CreateBody(groundBodyDef);<\/p>\n

\t\t\tvar groundShapeDef:b2PolygonDef = new b2PolygonDef();
\n\t\t\tgroundShapeDef.SetAsBox(50.0, 10.0);<\/p>\n

\t\t\tgroundBody.CreateShape(groundShapeDef);<\/p>\n

\t\t\t\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
\n\t\t\t\/\/ http:\/\/www.box2d.org\/wiki\/index.php?title=Manual\/AS3#Creating_a_Dynamic_Body
\n\t\t\t\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
\n\t\t\tvar bodyDef:b2BodyDef = new b2BodyDef();
\n\t\t\tbodyDef.position.Set(0.0, 4.0);
\n\t\t\t\/\/ var body:b2Body = world.CreateBody(bodyDef); \/\/ [mck]: old code
\n\t\t\tbody = world.CreateBody(bodyDef);<\/p>\n

\t\t\tvar shapeDef:b2PolygonDef = new b2PolygonDef();
\n\t\t\tshapeDef.SetAsBox(1.0, 1.0);
\n\t\t\tshapeDef.density = 1.0;
\n\t\t\tshapeDef.friction = 0.3;
\n\t\t\tbody.CreateShape(shapeDef);
\n\t\t\tbody.SetMassFromShapes();<\/p>\n

\t\t\t\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
\n\t\t\t\/\/ http:\/\/www.box2d.org\/wiki\/index.php?title=Manual\/AS3#Debug_Drawing
\n\t\t\t\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
\n\t\t\tvar debugDraw:b2DebugDraw = new b2DebugDraw();
\n\t\t\tdebugDraw.m_sprite = new Sprite();<\/p>\n

\t\t\taddChild(debugDraw.m_sprite);<\/p>\n

\t\t\tdebugDraw.m_drawScale = 30;
\n\t\t\tdebugDraw.m_fillAlpha = .25;
\n\t\t\tdebugDraw.m_lineThickness = 1;
\n\t\t\tdebugDraw.m_drawFlags = b2DebugDraw.e_shapeBit | b2DebugDraw.e_jointBit ;
\n\t\t\tworld.SetDebugDraw (debugDraw);<\/p>\n

\t\t\t\/\/
\n\t\t\taddEventListener(Event.ENTER_FRAME, onUpdateHandler, false, 0, true);
\n\t\t}<\/p>\n

\t\t\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
\n\t\t\/\/ http:\/\/www.box2d.org\/wiki\/index.php?title=Manual\/AS3#Simulating_the_World_.28of_Box2D.29
\n\t\t\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
\n\t\tpublic function onUpdateHandler(e:Event):void{<\/p>\n

\t\t\tvar timeStep:Number = 1.0 \/ 60.0;
\n\t\t\tvar iterations:Number = 10;<\/p>\n

\t\t\tworld.Step(timeStep, iterations);<\/p>\n

\t\t}<\/p>\n

\t} \/\/ end class<\/p>\n

} \/\/ end package<\/p>\n

[\/as]<\/p>\n

So all you need to do is CTRL+ENTER.<\/p>\n

And you will have something like this:<\/p>\n

[swf]http:\/\/www.matthijskamstra.nl\/blog\/wp-content\/uploads\/helloworldbox2d_nice.swf,520, 390[\/swf]<\/div>\n

Is this it? No, lets make it better.
\nTomorrow more<\/p>\n","protected":false},"excerpt":{"rendered":"

In my previous post I update the “Hello world” for box2D so that you can see something visual happening. You can find the original here: AS3: Hello Box2D. Today I will make it a little bit more attractive (remove trace). First we change some settings to make it more fun to watch at! The groundBodeDef […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22,3],"tags":[408,230,231,398,159],"class_list":["post-771","post","type-post","status-publish","format-standard","hentry","category-as3","category-flash","tag-as3","tag-box2d","tag-box2dflash","tag-flash","tag-flashdevelop"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t