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标题 基于html5 canvas实现漫天飞雪效果实例
内容
    本文实例讲述了基于html5 canvas实现漫天飞雪效果的方法，运行该实例可以看到很棒的下雪效果。如下图所示：
    名单
    主要代码如下：
    >">
    <html xmlns="<a href=">">
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
    <title>漫天飞雪</title>
    <style type="text/css">
    * {margin: 0; padding: 0;}</p> <p>body {
    /*You can use any kind of background here.*/
    background: #6b92b9;
    }
    canvas {
    display: block;
    }
    </style>
    </head></p> <p><body></p> <p><div ></div>
    <canvas id="canvas"></canvas></p> <p><script>
    window.onload = function(){
    //canvas init
    var canvas = document.getElementById("canvas");
    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 = 3000; //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()*3+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.fillStyle = "#FF0000";*/
    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 || p.x < 0 || 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 fromth
    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, 15);
    }
    </script>
    </body>
    </html>
    代码分析如下：
    这行代码改变雪花半径大小：
    复制代码代码如下:r: Math.random()*3+1, //radius
    这行代码改变雪花下落速度：
    复制代码代码如下:setInterval(draw, 15);
    这行值改变雪花密度：
    复制代码代码如下:var mp = 3000; //max particles
    相信本文所述对大家的html5 WEB程序设计有一定的借鉴价值。
随便看

　

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更新时间：2025/5/14 22:01:28