Efeito natalino de flocos de neve com canvas

Hou hou hou galera, natal está logo ai, e queria desejar tudo de bom para todos e desejar um 2015 melhor que 2014.

Estava precisando fazer alguma coisa no portal da empresa e achei esse efeito bem legal


Basta somente adicionar o canvas depois do body

 <canvas id="snowball"></canvas>  

O criar no onload da pagina a seguinte chamada

 window.onload = function(){  
      //canvas init  
      var canvas = document.getElementById("snowball");  
      var ctx = canvas.getContext("2d");  
      //canvas dimensions  
      var W = window.innerWidth;  
      var H = window.innerHeight;  
      canvas.width = W;  
      canvas.height = H;  
      //snowflake particles  
      var mp = 25; //max particles  
      var particles = [];  
      for(var i = 0; i < mp; i++){  
           particles.push({  
                x: Math.random()*W, //x-coordinate  
                y: Math.random()*H, //y-coordinate  
                r: Math.random()*4+1, //radius  
                d: Math.random()*mp //density  
           })  
      }  
      //Lets draw the flakes  
      function draw(){  
           ctx.clearRect(0, 0, W, H);  
           ctx.fillStyle = "rgba(255, 255, 255, 0.8)";  
           ctx.beginPath();  
           for(var i = 0; i < mp; i++){  
                var p = particles[i];  
                ctx.moveTo(p.x, p.y);  
                ctx.arc(p.x, p.y, p.r, 0, Math.PI*2, true);  
           }  
           ctx.fill();  
           update();  
      }  
      //Function to move the snowflakes  
      //angle will be an ongoing incremental flag. Sin and Cos functions will be applied to it to create vertical and horizontal movements of the flakes  
      var angle = 0;  
      function update(){  
           angle += 0.01;  
           for(var i = 0; i < mp; i++){  
                var p = particles[i];  
                //Updating X and Y coordinates  
                //We will add 1 to the cos function to prevent negative values which will lead flakes to move upwards  
                //Every particle has its own density which can be used to make the downward movement different for each flake  
                //Lets make it more random by adding in the radius  
                p.y += Math.cos(angle+p.d) + 1 + p.r/2;  
                p.x += Math.sin(angle) * 2;  
                //Sending flakes back from the top when it exits  
                //Lets make it a bit more organic and let flakes enter from the left and right also.  
                if(p.x > W+5 || p.x < -5 || p.y > H){  
                     if(i%3 > 0){ //66.67% of the flakes  
                          particles[i] = {x: Math.random()*W, y: -10, r: p.r, d: p.d};  
                     }else{  
                          //If the flake is exitting from the right  
                          if(Math.sin(angle) > 0){  
                               //Enter from the left  
                               particles[i] = {x: -5, y: Math.random()*H, r: p.r, d: p.d};  
                          }else{  
                               //Enter from the right  
                               particles[i] = {x: W+5, y: Math.random()*H, r: p.r, d: p.d};  
                          }  
                     }  
                }  
           }  
      }  
      //animation loop  
      setInterval(draw, 33);  
 };  

e depois utilizar o estilo

 #snowball{  
      position: absolute;  
      height: 100%;  
 }  

Fonte: http://thecodeplayer.com/walkthrough/html5-canvas-snow-effect

Por hoje é só pessoal, comentem compartilhem, de um +1 ai e qualquer dúvida é só deixar nos comentários ;)

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