仿知乎登录首页粒子动态背景

前段时间做了一个注册用户界面，需要美化一下背景：

[img]http://dl2.iteye.com/upload/attachment/0127/1580/f6249981-46fb-32ad-9a8b-d080e2693c45.png[/img]

配置文件:

/**
 * Particleground demo
 * @author Jonathan Nicol - @mrjnicol
 */

$(document).ready(function() {
  $('#particles').particleground({
    dotColor: '#eae8e8',
    lineColor: '#eae8e8'
  });
  $('.intro').css({
    'margin-top': -($('.intro').height() / 2)
  });
});

/**
 * Particleground
 *
 * @author Jonathan Nicol - @mrjnicol
 * @version 1.0.1
 * @description Creates a canvas based particle system background
 *
 * Inspired by:
 * http://requestlab.fr/
 * http://disruptivebydesign.com/
 * 
 * @license The MIT License (MIT)
 * 
 * Copyright (c) 2014 Jonathan Nicol - @mrjnicol
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
!function(a){function b(b,d){function e(){if(w){$canvas=a(''),v.prepend($canvas),p=$canvas[0],q=p.getContext("2d"),f();for(var b=Math.round(p.width*p.height/d.density),c=0;b>c;c++){var e=new l;e.setStackPos(c),x.push(e)}a(window).on("resize",function(){h()}),a(document).on("mousemove",function(a){y=a.pageX,z=a.pageY}),B&&!A&&window.addEventListener("deviceorientation",function(){D=Math.min(Math.max(-event.beta,-30),30),C=Math.min(Math.max(-event.gamma,-30),30)},!0),g(),o("onInit")}}function f(){p.width=v.width(),p.height=v.height(),q.fillStyle=d.dotColor,q.strokeStyle=d.lineColor,q.lineWidth=d.lineWidth}function g(){if(w){s=a(window).width(),t=a(window).height(),q.clearRect(0,0,p.width,p.height);for(var b=0;b=0;i--)(x[i].position.x>v.width()||x[i].position.y>v.height())&&x.splice(i,1);var a=Math.round(p.width*p.height/d.density);if(a>x.length)for(;a>x.length;){var b=new l;x.push(b)}else a=0;i--)x[i].setStackPos(i)}function j(){E=!0}function k(){E=!1,g()}function l(){switch(this.stackPos,this.active=!0,this.layer=Math.ceil(3*Math.random()),this.parallaxOffsetX=0,this.parallaxOffsetY=0,this.position={x:Math.ceil(Math.random()*p.width),y:Math.ceil(Math.random()*p.height)},this.speed={},d.directionX){case"left":this.speed.x=+(-d.maxSpeedX+Math.random()*d.maxSpeedX-d.minSpeedX).toFixed(2);break;case"right":this.speed.x=+(Math.random()*d.maxSpeedX+d.minSpeedX).toFixed(2);break;default:this.speed.x=+(-d.maxSpeedX/2+Math.random()*d.maxSpeedX).toFixed(2),this.speed.x+=this.speed.x>0?d.minSpeedX:-d.minSpeedX}switch(d.directionY){case"up":this.speed.y=+(-d.maxSpeedY+Math.random()*d.maxSpeedY-d.minSpeedY).toFixed(2);break;case"down":this.speed.y=+(Math.random()*d.maxSpeedY+d.minSpeedY).toFixed(2);break;default:this.speed.y=+(-d.maxSpeedY/2+Math.random()*d.maxSpeedY).toFixed(2),this.speed.x+=this.speed.y>0?d.minSpeedY:-d.minSpeedY}}function m(a,b){return b?void(d[a]=b):d[a]}function n(){v.find(".pg-canvas").remove(),o("onDestroy"),v.removeData("plugin_"+c)}function o(a){void 0!==d[a]&&d[a].call(u)}var p,q,r,s,t,u=b,v=a(b),w=!!document.createElement("canvas").getContext,x=[],y=0,z=0,A=!navigator.userAgent.match(/(iPhone|iPod|iPad|Android|BlackBerry|BB10|mobi|tablet|opera mini|nexus 7)/i),B=!!window.DeviceOrientationEvent,C=0,D=0,E=!1;return d=a.extend({},a.fn[c].defaults,d),l.prototype.draw=function(){q.beginPath(),q.arc(this.position.x+this.parallaxOffsetX,this.position.y+this.parallaxOffsetY,d.particleRadius/2,0,2*Math.PI,!0),q.closePath(),q.fill(),q.beginPath();for(var a=x.length-1;a>this.stackPos;a--){var b=x[a],c=this.position.x-b.position.x,e=this.position.y-b.position.y,f=Math.sqrt(c*c+e*e).toFixed(2);fv.width()&&(this.position.x=0-this.parallaxOffsetX);break;default:(this.position.x+this.speed.x+this.parallaxOffsetX>v.width()||this.position.x+this.speed.x+this.parallaxOffsetX<0)&&(this.speed.x=-this.speed.x)}switch(d.directionY){case"up":this.position.y+this.speed.y+this.parallaxOffsetY<0&&(this.position.y=v.height()-this.parallaxOffsetY);break;case"down":this.position.y+this.speed.y+this.parallaxOffsetY>v.height()&&(this.position.y=0-this.parallaxOffsetY);break;default:(this.position.y+this.speed.y+this.parallaxOffsetY>v.height()||this.position.y+this.speed.y+this.parallaxOffsetY<0)&&(this.speed.y=-this.speed.y)}this.position.x+=this.speed.x,this.position.y+=this.speed.y},l.prototype.setStackPos=function(a){this.stackPos=a},e(),{option:m,destroy:n,start:k,pause:j}}var c="particleground";a.fn[c]=function(d){if("string"==typeof arguments[0]){var e,f=arguments[0],g=Array.prototype.slice.call(arguments,1);return this.each(function(){a.data(this,"plugin_"+c)&&"function"==typeof a.data(this,"plugin_"+c)[f]&&(e=a.data(this,"plugin_"+c)[f].apply(this,g))}),void 0!==e?e:this}return"object"!=typeof d&&d?void 0:this.each(function(){a.data(this,"plugin_"+c)||a.data(this,"plugin_"+c,new b(this,d))})},a.fn[c].defaults={minSpeedX:.1,maxSpeedX:.7,minSpeedY:.1,maxSpeedY:.7,directionX:"center",directionY:"center",density:1e4,dotColor:"#666666",lineColor:"#666666",particleRadius:7,lineWidth:1,curvedLines:!1,proximity:100,parallax:!0,parallaxMultiplier:5,onInit:function(){},onDestroy:function(){}}}(jQuery),/**
 * requestAnimationFrame polyfill by Erik Möller. fixes from Paul Irish and Tino Zijdel
 * @see: http://paulirish.com/2011/requestanimationframe-for-smart-animating/
 * @see: http://my.opera.com/emoller/blog/2011/12/20/requestanimationframe-for-smart-er-animating
 * @license: MIT license
 */
function(){for(var a=0,b=["ms","moz","webkit","o"],c=0;c