很棒的下雪效果
代码奉上
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
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<title>漫天飞雪</title>
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<style type="text/css">
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* {margin: 0; padding: 0;}
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body {
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/*You can use any kind of background here.*/
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background: #6b92b9;
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}
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canvas {
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display: block;
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}
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</style>
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</head>
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<body>
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<div style=" background:#6b92b9; width:100%; height:2000px;" ></div>
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<canvas id="canvas" style="position:fixed; top:0px;left:0px;z-index:80;pointer-events:none;"></canvas>
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<script>
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window.onload = function(){
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//canvas init
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var canvas = document.getElementById("canvas");
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var ctx = canvas.getContext("2d");
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//canvas dimensions
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var W = window.innerWidth;
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var H = window.innerHeight;
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canvas.width = W;
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canvas.height = H;
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//snowflake particles
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var mp = 3000; //max particles
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var particles = [];
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for(var i = 0; i < mp; i++)
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{
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particles.push({
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x: Math.random()*W, //x-coordinate
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y: Math.random()*H, //y-coordinate
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r: Math.random()*3+1, //radius
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d: Math.random()*mp //density
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})
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}
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//Lets draw the flakes
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function draw()
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{
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ctx.clearRect(0, 0, W, H);
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ctx.fillStyle = "rgba(255, 255, 255, 0.8)";
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/* ctx.fillStyle = "#FF0000";*/
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ctx.beginPath();
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for(var i = 0; i < mp; i++)
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{
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var p = particles[i];
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ctx.moveTo(p.x, p.y);
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ctx.arc(p.x, p.y, p.r, 0, Math.PI*2, true);
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}
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ctx.fill();
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update();
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}
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//Function to move the snowflakes
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//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
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var angle = 0;
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function update()
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{
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angle += 0.01;
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for(var i = 0; i < mp; i++)
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{
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var p = particles[i];
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//Updating X and Y coordinates
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//We will add 1 to the cos function to prevent negative values which will lead flakes to move upwards
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//Every particle has its own density which can be used to make the downward movement different for each flake
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//Lets make it more random by adding in the radius
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p.y += Math.cos(angle+p.d) + 1 + p.r/2;
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p.x += Math.sin(angle) * 2;
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//Sending flakes back from the top when it exits
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//Lets make it a bit more organic and let flakes enter from the left and right also.
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if(p.x > W || p.x < 0 || p.y > H)
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{
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if(i%3 > 0) //66.67% of the flakes
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{
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particles[i] = {x: Math.random()*W, y: -10, r: p.r, d: p.d};
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}
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else
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{
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//If the flake is exitting from the right
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if(Math.sin(angle) > 0)
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{
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//Enter fromth
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particles[i] = {x: -5, y: Math.random()*H, r: p.r, d: p.d};
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}
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else
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{
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//Enter from the right
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particles[i] = {x: W+5, y: Math.random()*H, r: p.r, d: p.d};
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}
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}
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}
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}
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}
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//animation loop
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setInterval(draw, 15);
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}
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</script>
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</body>
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r: Math.random()*3+1, //radius
这行代码改变雪花半径大小
setInterval(draw, 15);
这个改变雪花下落速度
var mp = 3000; //max particles
这个值改变雪花密度