COCOS-HTML5-3.9版本学习（三）box2d物理引擎的测试

概述我也是刚学习这两种引擎的JS写法，具体我先给大家说下box2dLayer的结构把： var box2dLayer = cc.Layer.extend({ world: null, allowSleep: true, //允许睡眠 onEnter: function() { this._super(); }, init: function() { }, initBox2d: fun

我也是刚学习这两种引擎的Js写法，具体我先给大家说下Box2dLayer的结构把：

var Box2dLayer = cc.Layer.extend({	world: null,allowSleep: true,//允许睡眠	onEnter: function() {		this._super();	},init: function() {	},initBox2d: function(size) {		this.scheduleUpdate();	},addBallinWorld: function(p) {			},update: function(dt) {			}});

关于里面的两个参数，world 就是我们将要建造的物理世界，allowSleep，你当允许暂停把；

下来我们先看initBox2d的实现：

initBox2d: function(size) {		var b2Vec2 = Box2D.Common.Math.b2Vec2,b2BodyDef = Box2D.Dynamics.b2BodyDef,b2Body = Box2D.Dynamics.b2Body,b2FixtureDef = Box2D.Dynamics.b2FixtureDef,b2World = Box2D.Dynamics.b2World,b2@R_404_6632@gonShape = Box2D.Collision.Shapes.b2@R_404_6632@gonShape,b2CircleShape = Box2D.Collision.Shapes.b2CircleShape;		var g = new b2Vec2(0,-10); //重力系数		this.world = new b2World(g,this.allowSleep);		this.world.SetContinuousPhysics(true); //允许物理现象		var fixDef = new b2FixtureDef();		fixDef.density = 1.0; //密度		fixDef.friction = 0.8; //摩擦		fixDef.restitution = 1; //d性		var bodyDef = new b2BodyDef(); //创建刚体定义数据对象		bodyDef.type = b2Body.b2_staticBody; //为静态刚体,即不受碰撞影响		fixDef.shape = new b2@R_404_6632@gonShape(); //多边形		fixDef.shape.SetAsBox(20,2); //设置为矩形		bodyDef.position.Set(10,size.height / PTM_RATIO);		this.world.CreateBody(bodyDef).CreateFixture(fixDef); //世界创建刚体,刚体创建设备,设备拥有形状		//bottom		bodyDef.position.Set(10,-1.8);		this.world.CreateBody(bodyDef).CreateFixture(fixDef);		fixDef.shape.SetAsBox(2,14);		// left		bodyDef.position.Set(-1.8,13);		this.world.CreateBody(bodyDef).CreateFixture(fixDef);		// right		bodyDef.position.Set(26.8,13);		this.world.CreateBody(bodyDef).CreateFixture(fixDef);		this.scheduleUpdate();	},

一大堆的定义，其实也没啥就是定义了我们界面的4个边框可以碰撞，直接复制粘贴把；

然后就是给我们自己的物理模型添加物理属性：

addBallinWorld: function(p) {		var sprite = this.getChildByTag(TAG_SPRITE_MANAGER); //根据标记得到小球		sprite.setposition(p);		var b2BodyDef = Box2D.Dynamics.b2BodyDef,b2@R_404_6632@gonShape = Box2D.Collision.Shapes.b2@R_404_6632@gonShape;		var bodyDef = new b2BodyDef();		bodyDef.type = b2Body.b2_dynamicBody;		bodyDef.position.Set(p.x / PTM_RATIO,p.y / PTM_RATIO);		bodyDef.userData = sprite;		var body = this.world.CreateBody(bodyDef);		var dynamicBox = new b2@R_404_6632@gonShape();		dynamicBox.SetAsBox(0.5,0.5);		var fixtureDef = new b2FixtureDef();		fixtureDef.shape = dynamicBox;		fixtureDef.density = 1.0;		fixtureDef.friction = 0.3;		body.CreateFixture(fixtureDef);	},

然后是

update: function(dt) {		var veLocityIterations = 8;		var positionIterations = 1;		this.world.Step(dt,veLocityIterations,positionIterations);		for (var b = this.world.GetbodyList(); b; b = b.GetNext()) {			if (b.GetUserData() != null) {				var myActor = b.GetUserData();				myActor.x = b.Getposition().x * PTM_RATIO;				myActor.y = b.Getposition().y * PTM_RATIO;				myActor.rotation = -1 * cc.radiansToDegress(b.GetAngle());			}		}	}

好了，方法都架好了，然后让我们来实现：

onEnter: function() {		this._super();		this.init();	},init: function() {		var size = cc.director.getWinSize();		//添加背景		var bg = cc.Layercolor.create(cc.color(0,0));		bg.attr({			anchorX: 0,anchorY: 0,x: 0,y: 0		});		this.addChild(bg);		this.initBox2d(size); //初始化物理世界		var ball = cc.Sprite.create(res.BoxPNG,cc.rect(0,PTM_RATIO,PTM_RATIO));		this.addChild(ball,TAG_SPRITE_MANAGER); //给小球标记TAG		this.addBallinWorld(cc.p(size.wIDth / 2,size.height / 2)); //将小球加入物理世界	},

希望想学习的人和我一样写一写。

http://pan.baIDu.com/s/1ntVX6nZ 源码在这里。

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