Box2DFlash 基本示例程序

package{
	import Box2D.Collision.Shapes.b2PolygonShape;
	import Box2D.Common.Math.b2Vec2;
	import Box2D.Dynamics.b2Body;
	import Box2D.Dynamics.b2BodyDef;
	import Box2D.Dynamics.b2DebugDraw;
	import Box2D.Dynamics.b2FixtureDef;
	import Box2D.Dynamics.b2World;

	import flash.display.Sprite;
	import flash.events.Event;
	import flash.events.TimerEvent;
	import flash.utils.Timer;

	[SWF(width="800",height="600",frameRate="32",backgroundColor="0x000000")]
	public class First extends Sprite{
		private var world:b2World;
		private var timeStep:Number;
		private var iterations:uint;
		private var pixelsPerMeter:Number = 30;

		public function First(){
			createWorld();
			makeDebugDraw();
			createGround();
			addEventListener(Event.ENTER_FRAME,onEnterframe);
			var timer:Timer = new Timer(1000);
			timer.addEventListener(TimerEvent.TIMER,onTimer);
			timer.start();
		}

		private function createWorld():void{
			var gravity:b2Vec2 = new b2Vec2(0.0,9.8);
			var doSleep:Boolean = true;
			world = new b2World(gravity,doSleep);
			world.SetWarmStarting(true);
			timeStep = 1.0/30.0;
			iterations = 10;
		}

		private function makeDebugDraw():void{
			var debugDraw:b2DebugDraw = new b2DebugDraw();
			var debugSprite:Sprite = new Sprite();
			addChild(debugSprite);
			debugDraw.SetSprite(debugSprite);
			debugDraw.SetDrawScale(30.0);
			debugDraw.SetFillAlpha(0.5);
			debugDraw.SetLineThickness(1.0);
			debugDraw.SetFlags(b2DebugDraw.e_shapeBit | b2DebugDraw.e_jointBit);
			world.SetDebugDraw(debugDraw);
		}

		private function createGround():void{
			var bodyDef:b2BodyDef = new b2BodyDef();
			// Body的中心点
			bodyDef.position.Set(400/pixelsPerMeter,595/pixelsPerMeter);
			var body:b2Body = world.CreateBody(bodyDef);
			var shape:b2PolygonShape = new b2PolygonShape();
			// 几何体的半宽和半高
			shape.SetAsBox(400/pixelsPerMeter,5/pixelsPerMeter);
			body.CreateFixture2(shape);
		}

		private function onTimer(e:TimerEvent):void{
			var bodyDef:b2BodyDef = new b2BodyDef();
			bodyDef.type = b2Body.b2_dynamicBody;
			bodyDef.position.Set((Math.random()*400+120)/pixelsPerMeter,0);
			bodyDef.angle = Math.random()*Math.PI;
			var shape:b2PolygonShape = new b2PolygonShape();
			shape.SetAsBox((Math.random()*10+10)/pixelsPerMeter,(Math.random()*10+10)/pixelsPerMeter);
			var fixtureDef:b2FixtureDef = new b2FixtureDef();
			fixtureDef.shape = shape;
			fixtureDef.density = 1.0;
			fixtureDef.friction = 0.3;
			fixtureDef.restitution = 0.1;
			var body:b2Body = world.CreateBody(bodyDef);
			body.CreateFixture(fixtureDef);
		}

		private function onEnterframe(e:Event):void{
			world.Step(timeStep,iterations,iterations);
			world.ClearForces();
			world.DrawDebugData();
		}
	}
}
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