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What‘s the ball‘s orbit if they head for it‘s next ball.
<html>
<canvas id="ca"></canvas><script>
ca.width=ca.height=1000;
var centerX=ca.width/ 2,centerY=ca.height/2;
var g=ca.getContext(‘2d‘);
var ro=Math.min(ca.width,ca.height)/2/Math.sqrt(3),the=0;
var r=15;
var v=10;
var cnt=7;
function circle(x,y,r){
g.beginPath();
g.arc(x,y,r,0,360);
g.closePath();
g.fill();
}
function dot(ro,the){
var x=centerX+ro*Math.cos(the),y=centerY+ro*Math.sin(the);
circle(x,y,r);
}
function go(){
var ax=ro*Math.cos(the),ay=ro*Math.sin(the);
var bx=ro*Math.cos(the+Math.PI*2/cnt),by=ro*Math.sin(the+Math.PI/cnt*2);
var dx=bx-ax,dy=by-ay;
var d=Math.sqrt(dx*dx+dy*dy);
var mx=(ax*v+bx*(d-v))/d,my=(ay*v+by*(d-v))/d;
ro=Math.sqrt(mx*mx+my*my),the=Math.atan2(my,mx);
//r*=0.98;
//v*=0.99;
}
var move=setInterval(function(){
if(Math.abs(ro)<0.001){clearInterval(move);return;}
// g.clearRect(0,0,ca.width,ca.height);
go();
for(var i=0;i<cnt;i++)
dot(ro,the+i*2*Math.PI/cnt);
},100);
</script>
</html>
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原文地址：http://www.cnblogs.com/weidiao/p/4936566.html
