13 Comments

1. Brendan Lee
   Posted April 30, 2009 at 2:54 pm | Permalink

   Thanks ! I have something I quickly put together here:

   http://yourcall.ribbit.com/

   it’s kinda crummy ( my first Box2D project ) but I have a lot of love for the library!

   thanks for this…

   b

2. Zevan
   Posted April 30, 2009 at 6:10 pm | Permalink

   cool! Yeah, Box2D is just plain awesome

3. Brendan Lee
   Posted May 9, 2009 at 5:41 pm | Permalink

   Quick Question -

   I am trying to add a feature to your framework to move the “simulation boundary” boxes on stage resize firing.

   I can think of two options, the better ( in my opinion) being just physically moving them or affecting width | height on them on RESIZE ( them being the stage walls )

   How does this affect the Box2D world? It seems to not acknowledge when I move the boundaries … I guess I don’t know enough about it to know if this is breaking the simulation or not.

   It was also really hackish for me to crack into the y / x / width / height properties, if you might be able to suggest a better way, im all ears.

   *** WARNING THIS IS SUPER HACK CODE, I WAS JUST TRYING TO ACCESS THE PROPERTIES ****

   package util {

   import com.actionsnippet.qbox.*;
   import flash.display.*;

   public class DyBox2D extends QuickBox2D {

   // Constants:
   // Public Properties:
   // Private Properties:

   // Initialization:
   private var ceiling:QuickObject;
   private var rightwall:QuickObject;
   private var leftwall:QuickObject;
   private var floor:QuickObject;

   public function DyBox2D(main:MovieClip, param:Object=null)
   {
   super(main, param);

   }

   override public function createStageWalls(p:Object=null):void{
   var defaults:Object = {lineColor:0×000000, lineAlpha:1, fillColor:0xCCCCCC, fillAlpha:1};
   if (p == null){
   p = new Object();
   }

   for (var key:String in defaults){
   if (p[key] == null){
   p[key] = defaults[key];
   }
   }
   var sw:Number = main.stage.stageWidth / 30;
   var sh:Number = main.stage.stageHeight / 30;

   floor=addBox({x:sw / 2, y:sh, width:sw - 1, height:1, density:.0, lineColor: p.lineColor, lineAlpha: p.lineAlpha, fillColor: p.fillColor, fillAlpha: p.fillAllpha});
   leftwall=addBox({x:sw / 2, y:0, width:sw - 1, height:1, density:.0, lineColor: p.lineColor, lineAlpha: p.lineAlpha, fillColor: p.fillColor, fillAlpha: p.fillAllpha});
   ceiling=addBox({x:0, y:sh / 2, width:1, height:sh , density:.0, lineColor: p.lineColor, lineAlpha: p.lineAlpha, fillColor: p.fillColor, fillAlpha: p.fillAllpha});
   rightwall=addBox({x:sw, y:sh / 2, width:1, height:sh , density:.0, lineColor: p.lineColor, lineAlpha: p.lineAlpha, fillColor: p.fillColor, fillAlpha: p.fillAllpha});
   }

   public function moveStageWalls():void
   {

   var sw:Number = main.stage.stageWidth / 30;
   var sh:Number = main.stage.stageHeight / 30;

   //ceiling
   ceiling.bodyDef.position.y = sh / 2;
   ceiling.bodyDef.position.x = 0;
   ceiling.bodyDef.userData.width = 1;
   ceiling.bodyDef.userData.height = sh;

   //leftwall
   leftwall.bodyDef.position.y = 0;
   leftwall.bodyDef.position.x = sw / 2;
   leftwall.bodyDef.userData.width = sw - 1;
   leftwall.bodyDef.userData.height = 1;

   rightwall.bodyDef.position.y = sh/2;
   rightwall.bodyDef.position.x = sw;
   rightwall.bodyDef.userData.width = 1;
   rightwall.bodyDef.userData.height = sh;

   floor.bodyDef.position.y = sh;
   floor.bodyDef.position.x = sw / 2;
   floor.bodyDef.userData.width = sw - 1;
   floor.bodyDef.userData.height = 1;

   }

   // Public Methods:
   // Protected Methods:
   }

   }

   *** AND HERE IS HOW IM CALLING IT ***

   private function resizeHandler(event:Event):void {
   //trace(”resizeHandler: ” + event);
   //trace(”stageWidth: ” + stage.stageWidth + ” stageHeight: ” + stage.stageHeight);

   sim.moveStageWalls();

   }

   sorry if this seems spammy, any advice is much appreciated -

   b

4. Zevan
   Posted May 10, 2009 at 10:18 am | Permalink

   This should do the trick. Problem is that as far as I know you can’t resize rigid bodies in Box2D you need to destroy and recreate them:

   import com.actionsnippet.qbox.*;

   // setting debug:true, will use the Box2D debug rendering
   var sim:QuickBox2D = new QuickBox2D(this, {debug:true, gravityY:10});

   var box:QuickObject = sim.addBox({x:3, y:3, width:1, height:1});

   var resizing:Boolean = false;
   var walls:Array = new Array();
   stage.align=StageAlign.TOP_LEFT;
   stage.addEventListener(Event.RESIZE, onResizeStage);
   onResizeStage();
   function onResizeStage(evt:Event=null):void{
   var sw:Number = stage.stageWidth / 30;
   var sh:Number = stage.stageHeight / 30;

   // you could also stop the simulation sim.stop()
   // and only draw the walls once rather than over and over
   updateWalls();
   // you’ll need to loop through and do this to all bodies
   if (box.x > sw){
   box.x = sw - .5;
   }
   if (box.y > sh){
   box.y = sh - .5;
   }
   }

   function updateWalls():void{
   for (var i:int = 0; i if (walls[i]){
   walls[i].destroy();
   }
   }
   var sw:Number = stage.stageWidth / 30;
   var sh:Number = stage.stageHeight / 30;
   walls[0] = sim.addBox({x:sw / 2, y:sh, width:sw - 1, height:1, density:.0});
   walls[1] = sim.addBox({x:sw / 2, y:0, width:sw - 1, height:1, density:.0});
   walls[2] = sim.addBox({x:0, y:sh / 2, width:1, height:sh , density:.0});
   walls[3] = sim.addBox({x:sw, y:sh / 2, width:1, height:sh , density:.0});
   }

   // begins the simulation
   sim.start();
   sim.mouseDrag();

5. Brendan Lee
   Posted May 10, 2009 at 3:07 pm | Permalink

   Thanks Zevan !

   * as a ” further reading ” resource for anyone that happens upon this thread -

   http://www.box2d.org/wiki/index.php?title=Manual/AS3

6. brendan
   Posted May 18, 2009 at 11:42 am | Permalink

   thanks for you help, I used if for a super simple site for a very subtle effect, check out the results:

   http://brendanlee.org/

7. Zevan
   Posted May 18, 2009 at 11:51 am | Permalink

   No problem. Nice work. Cool site.

8. Mr.doob
   Posted June 8, 2009 at 4:51 pm | Permalink

   This is the kind of wrapper that you keep doing again and again every time you start a project that uses box2D. Good idea to get done with a reusable one!

   Having said that, a very interesting feature this could have would be to be able to turn the simulation in realtime mode.

   Usually the problem with box2d is that the same simulation will go faster or slower depending of the cpu power. Making it go realtime would be to keep it synchronised with the timer, doing as many world.steps as needed to catch up on the desired simulation. And interpolate the positions if needed. This will make all simulations run at the same time in any machine, but only the fps will change.

9. Zevan
   Posted June 9, 2009 at 8:33 am | Permalink

   That’s a good idea - I’ll give it a try… I think I recall seeing something about this on the Box2D forums…. (googling)

   Yeah, here it is. Thanks for the suggestion

10. Larsen
    Posted June 11, 2009 at 9:40 pm | Permalink

    Hi there,

    is it possible to scaleUp or scaleDown the created QuickObjects at runtime.

    When I start my application all QuickObjects should growUp to a bigger size.

    Thanks for any suggestions…

11. Zevan
    Posted June 12, 2009 at 3:28 pm | Permalink

    Hey Larsen,

    Unfortunately the only way to scale Box2D objects is to destroy them and re-create them…. have a look at some of the comments above and that should help..

12. Andrew
    Posted March 7, 2010 at 10:25 pm | Permalink

    This should do the trick. Problem is that as far as I know you can’t resize rigid bodies in Box2D you need to destroy and recreate them:

    import com.actionsnippet.qbox.*;

    // setting debug:true, will use the Box2D debug rendering
    var sim:QuickBox2D = new QuickBox2D(this, {debug:true, gravityY:10});

    var box:QuickObject = sim.addBox({x:3, y:3, width:1, height:1});

    var resizing:Boolean = false;
    var walls:Array = new Array();
    stage.align=StageAlign.TOP_LEFT;
    stage.addEventListener(Event.RESIZE, onResizeStage);
    onResizeStage();
    function onResizeStage(evt:Event=null):void{
    var sw:Number = stage.stageWidth / 30;
    var sh:Number = stage.stageHeight / 30;

    // you could also stop the simulation sim.stop()
    // and only draw the walls once rather than over and over
    updateWalls();
    // you’ll need to loop through and do this to all bodies
    if (box.x > sw){
    box.x = sw - .5;
    }
    if (box.y > sh){
    box.y = sh - .5;
    }
    }

    function updateWalls():void{
    for (var i:int = 0; i if (walls[i]){
    walls[i].destroy();
    }
    }
    var sw:Number = stage.stageWidth / 30;
    var sh:Number = stage.stageHeight / 30;
    walls[0] = sim.addBox({x:sw / 2, y:sh, width:sw - 1, height:1, density:.0});
    walls[1] = sim.addBox({x:sw / 2, y:0, width:sw - 1, height:1, density:.0});
    walls[2] = sim.addBox({x:0, y:sh / 2, width:1, height:sh , density:.0});
    walls[3] = sim.addBox({x:sw, y:sh / 2, width:1, height:sh , density:.0});
    }

    // begins the simulation
    sim.start();
    sim.mouseDrag();

    ……………………………………………………………………………………………
    function updateWalls():void{
    for (var i:int = 0; i if (walls[i]){
    walls[i].destroy();
    }
    }
    ……………………………………………………………………………………………
    i canot work it out.is that wrong?

13. d
    Posted October 23, 2010 at 3:09 am | Permalink

    thanks, looking forward to trying it out - appreciate it.

    d