js实现的牛顿摆效果

牛顿摆是一个1960年代发明的桌面演示装置，五个质量相同的球体由吊绳固定，彼此紧密排列。又叫：牛顿摆球、动量守恒摆球、永动球、物理撞球、碰碰球等。

(function(window,undefined){
  window.None || (window.None = {});
  //重力加速度
  var G=9.8;
  var PI=Math.PI;
  //帧频
  var FPS=48;
 
/*
//IE角度转换
function rorateIt(node,deg){
  //取得末变形前矩形的中点
  var rect = node.getBoundingClientRect(),
  cx1 = (rect.right - rect.left) / 2, // center x
  cy1 = (rect.bottom - rect.top) / 2, // center y
  deg2rad = Math.PI / 180,//角度转弧度
  rad = deg * deg2rad ,
  cos = Math.cos(rad),
  sin = Math.sin(rad);
  var ident = "DXImageTransform.Microsoft.Matrix";
  node.style.filter = "progid:"+ident +"(M11='1.0',sizingmethod='auto expand')";
  //http://www.satzansatz.de/cssd/onhavinglayout.html
  if(!node.currentStyle.hasLayout){//在IE7中，如果没有获得hasLayout，滤镜会失效
   node.style.writingMode = "tb-rl";
  }  
  var filter = node.filters.item(ident);
  // +-------+-------+
  // | M11 | M12 |
  // +-------+-------+
  // | M21 | M22 |
  // +-------+-------+
  filter.M11 = cos;     
  filter.M12 = -sin;     
  filter.M21 = sin;      
  filter.M22 = cos;     
  //取得当前中心
  rect = node.getBoundingClientRect();
  var cx = (rect.right - rect.left) / 2;
  var cy = (rect.bottom - rect.top) / 2;
  //调整此元素的坐标系，实现CSS3 transform-origin的功能
  node.style.marginLeft = cx1 - cx + "px";
  node.style.marginTop = cy1 - cy + "px";
}
 
 
  */
  //外部函数引用
  //是否IE
  function isIE(){
    return navigator.userAgent.indexOf("MSIE")>-1;
  }
  //获取当前样式
  function returnStyle(obj,styleName){ 
    var myObj = typeof obj == "string" ? document.getElementById(obj) : obj; 
    if(document.all){ 
      return eval("myObj.currentStyle." + styleName); 
    } else { 
      return eval("document.defaultView.getComputedStyle(myObj,null)." + styleName); 
    } 
  } 
  //外部函数引用
  //图片方法
  var img=function(src){
    var img=new Image();
    img.src=src;
    return img;
  }
  //方向类，以垂直向下为0度逆时针为正
  var face=function(deg,rad){
    //0-360
    this.unit='deg';
    if(rad)deg=180/PI*deg;
    this.deg=deg;
    this.rad=PI/180*this.deg;
  }
  //矢量类
  var vector=function(size,fx){
    var cstrct=this.constructor;
    this.size=size;
    this.face=fx||new face(0);
    fx=this.face;
    this.toHv=function(){
      var h=new cstrct(Math.sin(fx.rad)*size,90);
      var v=new cstrct(Math.cos(fx.rad)*size,0);
      return [h,v];    
    }
  }
  //继承，obj:需要从矢量继承的对象,arg:arguments
  vector.extend=function(obj,arg){
    vector.apply(obj,arg);
  }
  //矢量合并方法
  vector.merger=function(arrvector){
    if(arguments.length>1)arrvector=arguments;
    var cstrct=arrvector[0].constructor;
    var i=0,ilav=arrvector.length;
    var sum=[0,0];
    for(;i=m){
        self.rigid.rotate(new face(0),self.axis);
        clearTimeout(tid);
        i=-m;
        if(fun)fun();
        return;
      }
      var f=new face(y,'rad');
      self.rigid.rotate(f,axis=self.axis);
      i+=fm;
      tid=setTimeout(function(){self.swing.call(self,o,fun)},t);
    }
     
    this.moveTo=function(p){
      self.body.style.left=p.x+"px";
      self.body.style.top=p.y+"px";
    }
  }
   
  //世界
  None.world=function(param){
    //param:{force:[多个force对象]}
    this.param=param||{};
    this.config={
      //全局外力
      g:new a(G),
      className:'',
      width:'100%',
      height:'100%',
      left:0,
      top:-200,
      arrNav:['about','myWork','site','other','myTools'],
      imgW:60,
      imgN:5,
      sDeg:5,
      hitSound:'sounds/hit.wav',
      vol:0.1
    }
    this.init();
  };
  None.world.prototype={
    //初始化
    dom:{},
    init:function(){
      var c=this.config;
      var p=this.param;
      //dom    
      var dom=document.createElement("div");
      dom.className=c.className;
      dom.style.position="absolute";
      dom.style.width=p.width||c.width;
      dom.style.height=p.height||c.height;
      dom.style.left=(p.left||c.left) +"px";
      dom.style.top=(p.top||c.top) +"px";
      this.dom=dom;
      document.body.appendChild(this.dom);
    },
    //添加一个刚体
    addRigid:function(rigid,p){
      if(!(rigid instanceof Array)){
        rigid=[rigid];
      }
      if(!p)p=[point(0,0)];
      if(!(p instanceof Array))p=[p];
      for(var i=0,rl=rigid.length;i 
 

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