as3 starling using box2d
var debugSprite:Sprite = new Sprite();
addChild(debugSprite);
var debugDraw:b2DebugDraw = new b2DebugDraw();
debugDraw.SetSprite(debugSprite);
debugDraw.SetDrawScale(30);
debugDraw.SetLineThickness( 1.0);
debugDraw.SetAlpha(1);
debugDraw.SetFillAlpha(0.4);
debugDraw.SetFlags(b2DebugDraw.e_shapeBit);
PhysicsCore.World.SetDebugDraw(debugDraw);

mStarling = new Starling(Game, stage);
stage.stage3Ds[0].addEventListener(Event.CONTEXT3D_CREATE, onContextCreated);

private function onContextCreated(e:Event):void
{
   var debugSprite:Sprite=new Sprite();
   addChild(debugSprite);
   (mStarling.stage.getChildAt(0) as Game).setDebugDraw(debugSprite)
}

public function setDebugDraw(debugSprite:flash.display.Sprite):void{

   var debugDraw:b2DebugDraw = new b2DebugDraw();
   debugDraw.SetSprite(debugSprite);
   _world.SetDebugDraw(debugDraw);

}