[Box2D]四.添加皮肤

点这看效果

1.绘制皮肤

用flash cs新建fla文件，注意在绘制它们的时候要将注册点设置在中心，然后发布成swc，这里我提供我的皮肤，

主要用到了里面的两个元件FloorAsset和IconAsset，分别是地面和头像的皮肤．

下载skin.swc

2.引入皮肤

先上代码

package 
{	
	import Box2D.Collision.Shapes.b2PolygonShape;
	import Box2D.Common.Math.b2Vec2;
	import Box2D.Dynamics.b2Body;
	import Box2D.Dynamics.b2BodyDef;
	import Box2D.Dynamics.b2FixtureDef;
	import Box2D.Dynamics.b2World;
	
	import flash.display.DisplayObject;
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.events.MouseEvent;
	import flash.text.TextField;
	import flash.text.TextFieldAutoSize;
	import flash.text.TextFormat;
	
	[SWF(width="410",height="480")]
	public class Skin extends Sprite {
		
		private var stageWidth:Number = 410;			//舞台宽度
		private var stageHeight:Number = 480;			//舞台高度
		private var backgroundColor:uint = 0x333333;	//背景色
		
		private var world:b2World;                //Box2D世界
		private var worldScale:Number = 30;        //一米等于30像素
		private var timeStep:Number = 1 / 30;    //时间步,世界将在每一个时间步被更新
		
		//只是定义了时间步还不够。在每一步，每一个物理实体（physic entity）根据作用
		//于自身的作用力来更新（不包括睡眠状态）。处理这项任务的算法叫约束解算器
		//（constraint solver）。它是基于循环每一个约束然后解算来进行的，一次一个。
		private var velIterations:int = 10;        //速率约束解算器
		private var posIterations:int = 10;        //位置约束解算器
		
		public function Skin() {
			drawBackground();
			initWorld();
			createTip();
			createFloor();
			addEventListener(Event.ENTER_FRAME,onUpdate);
			stage.addEventListener(MouseEvent.CLICK,onStageClick);
		}
		
		private function onStageClick(event:MouseEvent):void {
			createIcon(mouseX,mouseY);
		}
		
		private function createTip():void {
			var tip:TextField = new TextField();
			var format:TextFormat = new TextFormat();
			format.color = 0xFFFFFF;
			tip.autoSize = TextFieldAutoSize.LEFT;
			tip.defaultTextFormat = format;
			tip.text = "点击，创建头像";
			addChild(tip);
			tip.x = (stageWidth - tip.width) / 2;
		}
		
		private function createIcon(x:Number,y:Number):void {
			var iconAsset:DisplayObject = new IconAsset();
			var bodyDef:b2BodyDef = new b2BodyDef();   //刚体定义
			bodyDef.type = b2Body.b2_dynamicBody;	   //动态刚体
			//设置刚体坐标,Box2D坐标用米来表示,注册点是中心点 
			bodyDef.position.Set(x/worldScale,y/worldScale);
			bodyDef.userData = new Object();
			bodyDef.userData.asset = iconAsset;
			addChild(iconAsset);
			
			var polygonShape:b2PolygonShape = new b2PolygonShape(); //创建多边形
			polygonShape.SetAsBox(iconAsset.width/2/worldScale,iconAsset.height/2/worldScale); //轴对称的矩形,半宽长和半高长
			
			var fixtureDef:b2FixtureDef = new b2FixtureDef(); //夹具(fixture)用于将形状绑定到刚体上
			fixtureDef.density = 1;			//密度
			fixtureDef.restitution = 0.1;	//弹性系数
			fixtureDef.friction = 0.1;		//摩擦系数
			fixtureDef.shape = polygonShape;
			
			var theRect:b2Body = world.CreateBody(bodyDef);
			theRect.CreateFixture(fixtureDef);	
			iconAsset.x = theRect.GetPosition().x * worldScale;
			iconAsset.y = theRect.GetPosition().y * worldScale;
		}
		
		private function initWorld():void {
			var gravity:b2Vec2 = new b2Vec2(0,9.81);    //重力
			//世界中的刚体静止时，可以允许他们进入睡眠状态,睡眠的刚体无需模拟
			var sleep:Boolean = true;
			world = new b2World(gravity,sleep);
		}
		
		//创建地面
		private function createFloor():void {
			var floorAsset:DisplayObject = new FloorAsset();	//地面皮肤
			var bodyDef:b2BodyDef = new b2BodyDef();	//刚体定义
			bodyDef.type = b2Body.b2_staticBody;   //刚体类型为静态
			bodyDef.userData = new Object();
			bodyDef.userData.asset = floorAsset; 
			//设置刚体坐标,Box2D坐标用米来表示，注册点是中心
			bodyDef.position.Set(floorAsset.width/2/worldScale,(stageHeight - floorAsset.height/2)/worldScale);	
			
			var polygonShape:b2PolygonShape = new b2PolygonShape(); //创建多边形
			polygonShape.SetAsBox(floorAsset.width/2/worldScale,floorAsset.height/2/worldScale);//轴对称的矩形,半宽长和半高长
			
			var fixtureDef:b2FixtureDef = new b2FixtureDef(); //夹具(fixture)用于将形状绑定到刚体上
			fixtureDef.density = 1;			//密度
			fixtureDef.restitution = 0.3;	//弹性系数
			fixtureDef.friction = 0.1;		//摩擦系数
			fixtureDef.shape = polygonShape;
			
			var theFloorBody:b2Body = world.CreateBody(bodyDef); //创建刚体
			theFloorBody.CreateFixture(fixtureDef);
			
			addChild(floorAsset);
			floorAsset.x = theFloorBody.GetPosition().x * worldScale;
			floorAsset.y = theFloorBody.GetPosition().y * worldScale;
		}
		
		private function onUpdate(e:Event):void {
			world.Step(timeStep,velIterations,posIterations);
			world.ClearForces();
			for (var body:b2Body = world.GetBodyList(); body; body = body.GetNext()) {
				if(body.GetUserData()) {
					body.GetUserData().asset.x = body.GetPosition().x * worldScale;
					body.GetUserData().asset.y = body.GetPosition().y * worldScale;
					body.GetUserData().asset.rotation = body.GetAngle() * 180 / Math.PI; //弧度转为度
				}
			}
		}
		
		private function drawBackground():void {
			graphics.beginFill(backgroundColor);
			graphics.drawRect(0,stageWidth,stageHeight);
			graphics.endFill();
		}
		
	}
}

引入skin.swc，然后运行

3.关键代码

为刚体添加皮肤，主要是bodyDef.userData

var iconAsset:DisplayObject = new IconAsset();

bodyDef.userData = new Object();

bodyDef.userData.asset = iconAsset;

addChild(iconAsset);

同步皮肤元件与刚体的位置和旋转角度

for (var body:b2Body = world.GetBodyList(); body; body = body.GetNext()) {

? ? if(body.GetUserData()) {

? ? ? ? body.GetUserData().asset.x = body.GetPosition().x * worldScale;

? ? ? ? body.GetUserData().asset.y = body.GetPosition().y * worldScale;

? ? ? ? body.GetUserData().asset.rotation = body.GetAngle() * 180 / Math.PI;

? ? }

}