【9RIA—ladeng6666】—【Box2D系列教程 4】创建静止不动的刚体

9RIA-ladeng6666

转载：9RIA游戏开发者社区（天地会）
作者：ladeng6666（拉登大叔）
作者博客：http://www.ladeng6666.com/blog/


【Box2D系列教程-导航帖】—拉登大叔出品（总贴）



在"掉落的苹果——b2Body"中，有一个地面，它是静止不动的，不随刚体下落(废话，地面掉落那是地震！)。我想特别说明一下静止固定刚体的创建方法。
在Box2D中，刚体是否为静止不动，由"形状需求"b2ShapeDef决定。具体的讲，质量density为0的刚体就是静止不动的。注意：我用的是Box2D 2.0.1

[Actionscript3] 纯文本查看 复制代码

var shapeRequest:b2PolygonDef = new b2PolygonDef();
//详细说明我们的需求
//---------------------------------
//设置密度density为0，即表示该刚体是静止不动的
shapeRequest.density = 0;
//---------------------------------
shapeRequest.friction = 0.3;
shapeRequest.restitution = 0.2;
shapeRequest.SetAsBox(w/30, h/30);

下面的例子中，掉落的小球会被固定的挡板挡住，然后一个个掉进下面的小槽内(你可以在"创建圆形刚体"一章回顾一下小球的创建方法)

[Actionscript3] 纯文本查看 复制代码

package  
{
    import Box2D.Collision.b2AABB;
    import Box2D.Collision.Shapes.b2CircleDef;
    import Box2D.Collision.Shapes.b2PolygonDef;
    import Box2D.Common.Math.b2Vec2;
    import Box2D.Dynamics.b2Body;
    import Box2D.Dynamics.b2BodyDef;
    import Box2D.Dynamics.b2DebugDraw;
    import Box2D.Dynamics.b2World;
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.events.MouseEvent;

    /**
     * [url]http://www.ladeng6666.com[/url]
     * @author ladeng6666
     */
    public class Main extends Sprite 
    {
        private var world:b2World;
        private var body:b2Body;

        private var life:Number = 0;
        private var interval:Number = 20;

        public function Main() 
        {
            createWorld();
            createDebug();
            createBody(stage.stageWidth/2,0);
            createWalls();

            addEventListener(Event.ENTER_FRAME, loop);
            stage.addEventListener(MouseEvent.MOUSE_DOWN, onStageMouseDown);
        }

        private function onStageMouseDown(e:MouseEvent):void 
        {
            createBody(mouseX,mouseY);
        }

        private function loop(e:Event):void 
        {
            world.Step(1 / 30, 10);
            if (life < interval) {
                life++;
            }else {
                createBody(120, 0);
                life = 0;
            }

        }

        private function createWorld():void 
        {
            //1.创建一个环境
            var environment:b2AABB = new b2AABB();
            environment.lowerBound = new b2Vec2( -100, -100);
            environment.upperBound = new b2Vec2(100, 100);
            //2.声明重力
            var gravity:b2Vec2 = new b2Vec2(0, 10);
            //3.睡着的对象是否模拟
            var doSleep:Boolean = true;
            //4.创建b2World世界
            world = new b2World(environment, gravity, doSleep);
        }

        private function createDebug():void 
        {
            var debugSprite:Sprite = new Sprite();
            addChild(debugSprite);

            var debugDraw:b2DebugDraw = new b2DebugDraw();
            debugDraw.m_sprite = debugSprite;
            debugDraw.m_drawScale = 30.0;
            debugDraw.m_fillAlpha = 0.5;
            debugDraw.m_lineThickness = 1.0;
            debugDraw.m_drawFlags = b2DebugDraw.e_shapeBit | b2DebugDraw.e_jointBit;

            world.SetDebugDraw(debugDraw);
        }

        private function createBody(posX:Number,posY:Number):void 
        {
            //1.创建刚体需求b2BodyDef
            var bodyRequest:b2BodyDef = new b2BodyDef();
            bodyRequest.position.Set(posX / 30, posY / 30);//记得米和像素的转换关系
            //2.Box2D世界工厂更具需求创建createBody()生产刚体
            body=world.CreateBody(bodyRequest);
            //3.创建敢提形状需求b2ShapeDef的子类
            //定义形状需求是b2CircleDef圆形
            var shapeRequest:b2CircleDef = new b2CircleDef();
            //详细说明我们的需求
            shapeRequest.density = 3;
            shapeRequest.friction = 0.3;
            shapeRequest.restitution = 0.2;
            shapeRequest.radius = 0.5;
            //4.b2Body刚体工厂根据需求createShape生产形状
            body.CreateShape(shapeRequest);
            body.SetMassFromShapes();
        }

        private function createWalls():void 
        {
            createStaticBody(stage.stageWidth / 2, stage.stageHeight, stage.stageWidth, 30);
            createStaticBody(120, 100, 80, 5, Math.PI / 8);
            createStaticBody(240, 270, 5, 40);
            createStaticBody(440, 270, 5, 40);
            createStaticBody(340, 310, 104, 5);
        }
        private function createStaticBody(posX:Number, posY:Number, w:Number, h:Number,angle:Number=0):b2Body {
            //1.创建刚体需求b2BodyDef
            var bodyRequest:b2BodyDef = new b2BodyDef();
            bodyRequest.position.Set(posX / 30, posY / 30);//记得米和像素的转换关系
            bodyRequest.angle = angle;

            //2.Box2D世界工厂更具需求创建createBody()生产刚体
            var staticBody:b2Body=world.CreateBody(bodyRequest);
            //3.创建敢提形状需求b2ShapeDef的子类
            var shapeRequest:b2PolygonDef = new b2PolygonDef();
            //详细说明我们的需求
            //---------------------------------
            //设置密度density为0，即表示该刚体是静止不动的
            shapeRequest.density = 0;
            //---------------------------------
            shapeRequest.friction = 0.3;
            shapeRequest.restitution = 0.2;
            shapeRequest.SetAsBox(w/30, h/30);
            //4.b2Body刚体工厂根据需求createShape生产形状
            staticBody.CreateShape(shapeRequest);
            staticBody.SetMassFromShapes();

            return staticBody;
        }

    }

}

下载：
OK 2012-06-07 创建静止的刚体.rar (438.38 KB, 下载次数: 3)

2018-2-5 15:50 上传

点击文件名下载附件