--------------------武汉加油！中国加油！----春天要来了----要有信念-----------------2020-02-07-----------------------------------------------------------------------------------------------
//用canvas实现雪花随机动态飘落
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<style>
body{
margin: 0;
padding: 0;
}
canvas{
background: #000;
}
</style>
<body>
<canvas id = "snow">
</canvas>
<script>
var canvas = document.getElementById('snow');
var context = canvas.getContext('2d');
// 获得可视区的宽高
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
function snow(){
context.save();
// 开启路径
context.beginPath();
// 移动画布，确定雪花终点为中心点
context.translate(100,100);
//起点
context.moveTo(-20,0);
// 终点
context.lineTo(20,0);
// 线变成白色
context.strokeStyle = '#fff';
// 线变粗
context.lineWidth = 10;
// 线变圆头
context.lineCap = 'round';
context.stroke();
// 角度转弧度
var disX = Math.sin(30*Math.PI/180)*20;
var disY = Math.sin(60*Math.PI/180)*20;
// 画第二条线，左下到右上的线
context.moveTo(-disX,disY);
context.lineTo(disX,-disY);
// 画第三条线
context.moveTo(-disX,-disY);
context.lineTo(disX,disY);
context.stroke();
context.restore();
}
// snow();
//生成雪花的构造函数
function Snow(x,y,scale,rotate,speedX,speedY,speedR){
this.x = x;
this.y = y;
this.scale = scale;
this.rotate = rotate;
this.speedX = speedX;
this.speedY = speedY;
this.speedR = speedR;
// 渲染雪花
this.render = function(){
context.save();
context.beginPath();
context.translate(this.x,this.y);
context.scale(this.scale,this.scale);
context.rotate(this.rotate*Math.PI/180);
context.moveTo(-20,0);
context.lineTo(20,0);
context.strokeStyle = '#fff';
context.lineWidth = 10;
context.lineCap = 'round';
context.stroke();
var disX = Math.sin(30*Math.PI/180)*20;
var disY = Math.sin(60*Math.PI/180)*20;
context.moveTo(-disX,disY);
context.lineTo(disX,-disY);
context.moveTo(-disX,-disY);
context.lineTo(disX,disY);
context.stroke();
context.restore();
}
}
// var snow = new Snow(50,50,1,10,10,10,10);
// snow.render();
// 存储所有生成的雪花
var snowArray = [];
// 生成雪花
function init(){
var len = 100;
for(var i = 0;i<len;i++){
var x = Math.random()*canvas.width;
var scale = Math.random()+0.5;
var rotate = Math.random()*60;
var speedX = Math.random()+1
var speedY = Math.random()+5;
var speedR = Math.random()*4+2;
// var snow = new Snow(x,0,scale,rotate,speedX,speedY,speedR);
// snow.render();
(function(x,y,scale,rotate,speedX,speedY,speedR){
setTimeout(function(){
var snow = new Snow(x,0,scale,rotate,speedX,speedY,speedR);
snow.render();
snowArray.push(snow);
},Math.random()*8000);
})(x,0,scale,rotate,speedX,speedY,speedR);
}snowing();
}init();
// 动起来
function snowing(){
setInterval(function(){
//先清除
context.clearRect(0,0,canvas.width,canvas.height);
for(var i = 0;i < snowArray.length;i++){
snowArray[i].x = (snowArray[i].x+snowArray[i].speedX)%canvas.width;
snowArray[i].y = (snowArray[i].y+snowArray[i].speedY)%canvas.height;
snowArray[i].rotate = (snowArray[i].rotate+snowArray[i].speedR)%60;
snowArray[i].render();
}
},30);
}
/**
* sin60 = 对边/斜边 => 对边 = sin60*斜边 => y=sin60*半径（r）；
*/
</script>
</body>
</html>
