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<ilav;i++){
      var hv=arrvector[i].toHv();
      sum[0]+=hv[0].size;
      sum[1]+=hv[1].size;
    }
    var size=Math.sqrt(sum[0]*sum[0]+sum[1]*sum[1]);
    var fa=new face(Math.atan(sum[0]/sum[1]),'rad');
    return new cstrct(size,fa);
  }
  //力类,参数为大小和方向
  var force=function(size,face){
    this.unit='N';
    //继承自矢量
    vector.apply(this,arguments);
  }
  //加速度类
  var a=function(size,face){
    this.unit='m/s^2';
    vector.extend(this,arguments);
  }
  //速度类
  var speed=function(size,face){
    this.unit='m/s';
    vector.extend(this,arguments);
  }
 
  //刚体类,参数(body:IMG对象,m为质量)
  var rigid=function(body,m){
    //一般情况下body为一个img对象，所以暂且只有正方形或长方形两种形式
    this.body=body; 
    this.m=m;      //质量
    this.focus=(this.body instanceof Image)?point(this.body.width/2,this.body.height/2):point(this.body.style.width/2,this.body.style.height/2);
    this.axis=point(0,0);  //轴心位置(point对象)
     
    this.force=new force(0);
    this.a=new a(this.force.size/this.m,this.force.face);
    this.speed=new speed(0);
    //设置，可重新设置上面所有参数
    this.set=function(prop,value){
      this[prop]=value;
    }
    this.addForce=function(f){
      return this.force=vector.merger(f,this.force);
    }
       
    //旋转
    this.rotate=function(face,axis){
      axis=axis||this.axis||this.focus;
      //cx1=returnStyle(this.body,"left");
      //cy1=returnStyle(this.body,"left");
      var rect=this.body.getBoundingClientRect(),
      //cx1=rect.left+axis.x,
      //cy1=rect.top+axis.y,
      cx1 = (rect.right - rect.left) / 2,
      cy1 = (rect.bottom - rect.top) / 2,
      rad=face.rad,
      cos = Math.cos(rad),
      sin = Math.sin(rad);
      if(isIE()){
        var ident = "DXImageTransform.Microsoft.Matrix";
        this.body.style.filter = "progid:"+ident +"(M11='1.0',sizingmethod='auto expand')";
        if(!returnStyle(this.body,"hasLayout")){//在IE7中，如果没有获得hasLayout，滤镜会失效
          this.body.style.writingMode = "tb-rl";
        }  
        var filter = this.body.filters.item(ident);
        filter.M11 = cos;     
        filter.M12 = -sin;     
        filter.M21 = sin;      
        filter.M22 = cos;  
      }
      rect = this.body.getBoundingClientRect();
      //var cx=rect.left+axis.x;
      //var cy=rect.top+axis.y;
      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
      this.body.style.left=parseInt(this.body.style.left,10) + cx1 - cx + "px";
      this.body.style.top=parseInt(this.body.style.top,10) + cy1 - cy + "px";
      //CSS3
      var sdeg="rotate("+face.deg+"deg)";
      var paxis=axis.x+"px "+axis.y+"px";
      this.body.style.transformOrigin=paxis;
      this.body.style.MozTransformOrigin=paxis;
      this.body.style.WebkitTransformOrigin=paxis;
      this.body.style.OTransformOrigin=paxis;
      this.body.style.WebkitTransform=sdeg;
      this.body.style.MozTransform=sdeg;
      this.body.style.OTransform=sdeg;
      this.body.style.transform=sdeg;
    }
  }
  //刚体组合
  rigid.merger=function(){
     
  }
  //无弹性绳子类
  var rope=function(body,length,maxForce){
    this.body=body;
    this.length=length;
    this.maxForce=maxForce || Infinity || Number.MAX_VALUE;
  }
  //组合体类
  var comb=function(arrObject){
     
  }
  //单摆类
  var pendulum=function(ripe,rigid){
     
  }
   
  //类单摆
  var likePend=function(rigid,fa,time){//刚体,初始角度,摆动频率
    var self=this;
    this.rigid=rigid;
    this.body=this.rigid.body;
    this.axis=this.rigid.axis;
    this.dom=this.rigid.dom;
    this.m=this.rigid.m;
    this.rad=fa?fa.rad:fa=new face(PI/6,'rad');
    //摆动
    //角度30
    var fx=fa.rad;
    //角度平方根
    var m=Math.sqrt(fx);
    //摆动时间1秒
    var atime=time||0.5;
    var fnum=FPS*atime;
    //单位增量
    var fm=m/fnum;
    //i:角度平方根到0
    var i=-m,tid;
    var g=new a(G);
    var t=1000/FPS;
    //o:{s:1,f:30,t:0,fun:callback}  :s:(-1,1)速度增加还是减小,f:从多少度,t:到多少度,fun:摆完后运行的函数
    this.swing=function(o,fun){
/*     var asps=g.size*Math.cos(PI/2-fx)/(24*24*self.m); 
      var fss=new force(asps,new face(fx-PI/2));
      this.rigid.force=fss;
      var a=this.rigid.a;
      //单位时间内速度的增量
      var a1=Math.acos((asps+this.rigid.speed.size)/2)
      this.rigid.speed=new speed(a1,new face(fx-PI/2));
      a2=a1*2;*/
      //{s:-1,inc:1}
      o=o||{s:1};
      var y=-o.s*i*i+fx*o.s;
      if(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<rl;i++){
        p[i]=p[i] || p[0];
        rigid[i].body.style.position="absolute";
        rigid[i].body.style.left=p[i].x+"px";
        rigid[i].body.style.top=p[i].y+"px";
        this.dom.appendChild(rigid[i].body);
      }
    },
    //添加一个外作用力
    addForce:function(){
       
    },
    start:function(){
      var p=this.param,
      c=this.config;
      var shit=p.hitSound||c.hitSound;
      var sndHit=new None.sounds(shit);
      sndHit.volume=p.vol||c.vol;
      var w=document.documentElement.offsetWidth;
      var imgWidth=p.imgW||c.imgW;//图片宽度
      var imgNum=p.imgN||c.imgN; //图片数量
      var jd=p.sDeg||c.sDeg;   //最大角度
      var es=p.arrNav||c.arrNav;
      var time=p.time||c.time;
       
      var basex=w/2-imgWidth*imgNum/2;
      var jiaodu=new face(jd);
      var rig=[],ball=[],pend=[],axis=point(imgWidth/2,0);
      for(var i=0,el=es.length;i<el;i++){
        rig[i]=document.getElementById(es[i]);
        ball[i]=new rigid(rig[i],1);
        ball[i].set("axis",axis);
        pend[i]=new likePend(ball[i],jiaodu,time);
      }
      this.addRigid(pend);
      resize();
      if(!isIE())swing();
      window.onresize=resize;
       
      function hit(v){
        sndHit.play(); 
      }
      function swing(){
        var runfun=arguments.callee;
        var last=pend.length-1;
        if(p.hitSound)hit(0);
        pend[0].swing({s:1},function(){
          if(p.hitSound)hit(1);
          pend[last].swing({s:-1},runfun);
        });
      }
      function resize(){
        var w=document.documentElement.offsetWidth;
        var basex=w/2-imgWidth*imgNum/2;
        var n=pend.length;
        for(var i=0;i<n;i++){
          pend[i].moveTo(point(basex+imgWidth*i,0)); 
        }
      }  
    }
  };
   
})(window);

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