<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>ѩ��</title>
<script type="text/javascript" src="js/jquery.min.js"></script>
<style>
html,body {
width: 100%;
height: 100%;
margin: 0;
padding: 0;
overflow: hidden;
}
.container{
width: 100%;
height: 100%;
margin: 0;
padding: 0;
}</style>
</head>
<body>
<div id="jsi-snow-container" class="container"></div>
<script>
var RENDERER = {
SNOW_COUNT: {INIT : 100, DELTA : 1},
BACKGROUND_COLOR : 'hsl(%h, 50%, %l%)',
INIT_HUE : 180,
DELTA_HUE : 0.1,
init : function(){
this.setParameters();
this.reconstructMethod();
this.createSnow(this.SNOW_COUNT.INIT * this.countRate, true);
this.render();
},
setParameters : function(){
this.$window = $(window);
this.$container = $('#jsi-snow-container');
this.width = this.$container.width();
this.height = this.$container.height();
this.center = {x : this.width / 2, y : this.height / 2};
this.countRate = this.width * this.height / 500 / 500;
this.canvas = $('<canvas />').attr({width : this.width, height : this.height}).appendTo(this.$container).get(0);
this.context = this.canvas.getContext('2d');
this.radius = Math.sqrt(this.center.x * this.center.x + this.center.y * this.center.y);
this.hue = this.INIT_HUE;
this.snows = [];
},
reconstructMethod : function(){
this.render = this.render.bind(this);
},
createSnow : function(count, toRandomize){
for(var i = 0; i < count; i++){
this.snows.push(new SNOW(this.width, this.height, this.center, toRandomize));
}
},
render : function(){
requestAnimationFrame(this.render);
var gradient = this.context.createRadialGradient(this.center.x, this.center.y, 0, this.center.x, this.center.y, this.radius),
backgroundColor = this.BACKGROUND_COLOR.replace('%h', this.hue);
gradient.addColorStop(0, backgroundColor.replace('%l', 30));
gradient.addColorStop(0.2, backgroundColor.replace('%l', 20));
gradient.addColorStop(1, backgroundColor.replace('%l', 5));
this.context.fillStyle = gradient;
this.context.fillRect(0, 0, this.width, this.height);
for(var i = this.snows.length - 1; i >= 0; i--){
if(!this.snows[i].render(this.context)){
this.snows.splice(i, 1);
}
}
this.hue += this.DELTA_HUE;
this.hue %= 360;
this.createSnow(this.SNOW_COUNT.DELTA, false);
}
};
var SNOW = function(width, height, center, toRandomize){
this.width = width;
this.height = height;
this.center = center;
this.init(toRandomize);
};
SNOW.prototype = {
RADIUS : 20,
OFFSET : 4,
INIT_POSITION_MARGIN : 20,
COLOR : 'rgba(255, 255, 255, 0.8)',
TOP_RADIUS : {MIN : 1, MAX : 3},
SCALE : {INIT : 0.04, DELTA : 0.01},
DELTA_ROTATE : {MIN : -Math.PI / 180 / 2, MAX : Math.PI / 180 / 2},
THRESHOLD_TRANSPARENCY : 0.7,
VELOCITY : {MIN : -1, MAX : 1},
LINE_WIDTH : 2,
BLUR : 10,
init : function(toRandomize){
this.setParameters(toRandomize);
this.createSnow();
},
setParameters : function(toRandomize){
if(!this.canvas){
this.radius = this.RADIUS + this.TOP_RADIUS.MAX * 2 + this.LINE_WIDTH;
this.length = this.radius * 2;
this.canvas = $('<canvas />').attr({width : this.length, height : this.length}).get(0);
this.context = this.canvas.getContext('2d');
}
this.topRadius = this.getRandomValue(this.TOP_RADIUS);
var theta = Math.PI * 2 * Math.random();
this.x = this.center.x + this.INIT_POSITION_MARGIN * Math.cos(theta);
this.y = this.center.y + this.INIT_POSITION_MARGIN * Math.sin(theta);
this.vx = this.getRandomValue(this.VELOCITY);
this.vy = this.getRandomValue(this.VELOCITY);
this.deltaRotate = this.getRandomValue(this.DELTA_ROTATE);
this.scale = this.SCALE.INIT;
this.deltaScale = 1 + this.SCALE.DELTA * 500 / Math.max(this.width, this.height);
this.rotate = 0;
if(toRandomize){
for(var i = 0, count = Math.random() * 1000; i < count; i++){
this.x += this.vx;
this.y += this.vy;
this.scale *= this.deltaScale;
this.rotate += this.deltaRotate;
}
}
},
getRandomValue : function(range){
return range.MIN + (range.MAX - range.MIN) * Math.random();
},
createSnow : function(){
this.context.clearRect(0, 0, this.length, this.length);
this.context.save();
this.context.beginPath();
this.context.translate(this.radius, this.radius);
this.context.strokeStyle = this.COLOR;
this.context.lineWidth = this.LINE_WIDTH;
this.context.shadowColor = this.COLOR;
this.context.shadowBlur = this.BLUR;
var angle60 = Math.PI / 180 * 60,
sin60 = Math.sin(angle60),
cos60 = Math.cos(angle60),
threshold = Math.random() * this.RADIUS / this.OFFSET | 0,
rate = 0.5 + Math.random() * 0.5,
offsetY = this.OFFSET * Math.random() * 2,
offsetCount = this.RADIUS / this.OFFSET;
for(var i = 0; i < 6; i++){
this.context.save();
this.context.rotate(angle60 * i);
for(var j = 0; j <= threshold; j++){
var y = -this.OFFSET * j;
this.context.moveTo(0, y);
this.context.lineTo(y * sin60, y * cos60);
}
for(var j = threshold; j < offsetCount; j++){
var y = -this.OFFSET * j,
x = j * (offsetCount - j + 1) * rate;
this.context.moveTo(x, y - offsetY);
this.context.lineTo(0, y);
this.context.lineTo(-x, y - offsetY);
}
this.context.moveTo(0, 0);
this.context.lineTo(0, -this.RADIUS);
this.context.arc(0, -this.RADIUS - this.topRadius, this.topRadius, Math.PI / 2, Math.PI * 2.5, false);
this.context.restore();
}
this.context.stroke();
this.context.restore();
},
render : function(context){
context.save();
if(this.scale > this.THRESHOLD_TRANSPARENCY){
context.globalAlpha = Math.max(0, (1 - this.scale) / (1 - this.THRESHOLD_TRANSPARENCY));
if(this.scale > 1 || this.x < -this.radius || this.x > this.width + this.radius || this.y < -this.radius || this.y > this.height + this.radius){
context.restore();
return false;
}
}
context.translate(this.x, this.y);
context.rotate(this.rotate);
context.scale(this.scale, this.scale);
context.drawImage(this.canvas, -this.radius, -this.radius);
context.restore();
this.x += this.vx;
this.y += this.vy;
this.scale *= this.deltaScale;
this.rotate += this.deltaRotate;
return true;
}
};
$(function(){
RENDERER.init();
});</script>
</body>
</html>
