JavaScript canvas實現雪花隨機動態飄落
阿新 • • 發佈：2020-02-10
用canvas實現雪花隨機動態飄落，供大家參考，具體內容如下
<!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');
// 獲得可視區的寬高
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
function snow(){
context.save();
// 開啟路徑
context.beginPath();
// 移動畫布，確定雪花終點為中心點
context.translate(100,100);
//起點
context.moveTo(-20,0);
// 終點
context.lineTo(20,0);
// 線變成白色
context.strokeStyle = '#fff';
// 線變粗
context.lineWidth = 10;
// 線變圓頭
context.lineCap = 'round';
context.stroke();
// 角度轉弧度
var disX = Math.sin(30*Math.PI/180)*20;
var disY = Math.sin(60*Math.PI/180)*20;
// 畫第二條線，左下到右上的線
context.moveTo(-disX,disY);
context.lineTo(disX,-disY);
// 畫第三條線
context.moveTo(-disX,-disY);
context.lineTo(disX,disY);
context.stroke();
context.restore();
}
// snow();
//生成雪花的建構函式
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);
// snow.render();
// 儲存所有生成的雪花
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,speedR);
// snow.render();
(function(x,speedR){
setTimeout(function(){
var snow = new Snow(x,speedR);
snow.render();
snowArray.push(snow);
},Math.random()*8000);
})(x,speedR);
}snowing();
}init();
// 動起來
function snowing(){
setInterval(function(){
//先清除
context.clearRect(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 = 對邊/斜邊 => 對邊 = sin60*斜邊 => y=sin60*半徑（r）；
*/
</script>
</body>
</html>以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支援我們。