눈 내리는 효과.. ( JS + CSS )

 

    

 

Demo & Code

 

 

[Demo] Snowing effect~

 

 

<!-- HTML -->

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

 

 

/* CSS */

#canvas {
  width:1000px; height:500px; top:50%; left:50%; transform:translate(-50%, -50%);
  background-image:url(이미지 경로); background-size:cover
}

 

 

 

/*Javascrpt*/

(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();