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js-snow-4.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
body{
background: #000;
}
</style>
</head>
<script type="text/javascript">
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>
<canvas id="canvas"></canvas>
</body>
</html>