Created
December 24, 2012 07:05
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Snow animation
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<canvas id="canvas"></canvas> |
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(function() { | |
var requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame || window.msRequestAnimationFrame || | |
function(callback) { | |
window.setTimeout(callback, 1000 / 60); | |
}; | |
window.requestAnimationFrame = requestAnimationFrame; | |
})(); | |
var flakes = [], | |
canvas = document.getElementById("canvas"), | |
ctx = canvas.getContext("2d"), | |
flakeCount = 400, | |
mX = -100, | |
mY = -100 | |
canvas.width = window.innerWidth; | |
canvas.height = window.innerHeight; | |
function snow() { | |
ctx.clearRect(0, 0, canvas.width, canvas.height); | |
for (var i = 0; i < flakeCount; i++) { | |
var flake = flakes[i], | |
x = mX, | |
y = mY, | |
minDist = 150, | |
x2 = flake.x, | |
y2 = flake.y; | |
var dist = Math.sqrt((x2 - x) * (x2 - x) + (y2 - y) * (y2 - y)), | |
dx = x2 - x, | |
dy = y2 - y; | |
if (dist < minDist) { | |
var force = minDist / (dist * dist), | |
xcomp = (x - x2) / dist, | |
ycomp = (y - y2) / dist, | |
deltaV = force / 2; | |
flake.velX -= deltaV * xcomp; | |
flake.velY -= deltaV * ycomp; | |
} else { | |
flake.velX *= .98; | |
if (flake.velY <= flake.speed) { | |
flake.velY = flake.speed | |
} | |
flake.velX += Math.cos(flake.step += .05) * flake.stepSize; | |
} | |
ctx.fillStyle = "rgba(255,255,255," + flake.opacity + ")"; | |
flake.y += flake.velY; | |
flake.x += flake.velX; | |
if (flake.y >= canvas.height || flake.y <= 0) { | |
reset(flake); | |
} | |
if (flake.x >= canvas.width || flake.x <= 0) { | |
reset(flake); | |
} | |
ctx.beginPath(); | |
ctx.arc(flake.x, flake.y, flake.size, 0, Math.PI * 2); | |
ctx.fill(); | |
} | |
requestAnimationFrame(snow); | |
}; | |
function reset(flake) { | |
flake.x = Math.floor(Math.random() * canvas.width); | |
flake.y = 0; | |
flake.size = (Math.random() * 3) + 2; | |
flake.speed = (Math.random() * 1) + 0.5; | |
flake.velY = flake.speed; | |
flake.velX = 0; | |
flake.opacity = (Math.random() * 0.5) + 0.3; | |
} | |
function init() { | |
for (var i = 0; i < flakeCount; i++) { | |
var x = Math.floor(Math.random() * canvas.width), | |
y = Math.floor(Math.random() * canvas.height), | |
size = (Math.random() * 3) + 2, | |
speed = (Math.random() * 1) + 0.5, | |
opacity = (Math.random() * 0.5) + 0.3; | |
flakes.push({ | |
speed: speed, | |
velY: speed, | |
velX: 0, | |
x: x, | |
y: y, | |
size: size, | |
stepSize: (Math.random()) / 30, | |
step: 0, | |
opacity: opacity | |
}); | |
} | |
snow(); | |
}; | |
canvas.addEventListener("mousemove", function(e) { | |
mX = e.clientX, | |
mY = e.clientY | |
}); | |
window.addEventListener("resize",function(){ | |
canvas.width = window.innerWidth; | |
canvas.height = window.innerHeight; | |
}) | |
init(); |
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body{margin:0;height:100%;} | |
canvas{ | |
position:absolute;top:0;left:0 | |
background-image: linear-gradient(bottom, rgb(105,173,212) 0%, rgb(23,82,145) 84%); | |
background-image: -o-linear-gradient(bottom, rgb(105,173,212) 0%, rgb(23,82,145) 84%); | |
background-image: -moz-linear-gradient(bottom, rgb(105,173,212) 0%, rgb(23,82,145) 84%); | |
background-image: -webkit-linear-gradient(bottom, rgb(105,173,212) 0%, rgb(23,82,145) 84%); | |
background-image: -ms-linear-gradient(bottom, rgb(105,173,212) 0%, rgb(23,82,145) 84%); | |
background-image: -webkit-gradient( | |
linear, | |
left bottom, | |
left top, | |
color-stop(0, rgb(105,173,212)), | |
color-stop(0.84, rgb(23,82,145)) | |
); | |
} |
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