好看漂亮的html5网页特效学习笔记(4)——canvas实现火焰跟随鼠标

效果:

  • 逼真的火焰跟随鼠标,还冒出火花,照亮背景文字
  • 使用canvas绘制
  • 使用javascript,但并无复杂逻辑。上手程度:简单
  • 欢迎来我的博客看此文章: https://clatterrr.com/archives/1606

源码:

学习笔记:

google字体

在上一篇中已讲过。好看漂亮的html5网页特效学习笔记(3)_猜猜下一个颜色是什么?

javascript分步详细解释

第一步:

很简单的初始化函数。

var oCanvas;
init = function()
{
 
	oCanvas = new Fire();
	oCanvas.run();
}
window.onload = init;

 

第二步:

初始化canvas,定义各种基础的东西,以及为鼠标添加事件监测。addEventListener第三个参数的意思是,若为false,则为事件处理顺序为先进先处理,为true则为先进后处理。具体请看https://www.runoob.com/jsref/met-element-addeventlistener.html

var Fire  = function(){

	this.canvas 		= document.getElementById('fire');
	this.ctx 			= this.canvas.getContext('2d');
	this.canvas.height 	= window.innerHeight;
	this.canvas.width 	= window.innerWidth;

	this.aFires 		= [];
	this.aSpark 		= [];
	this.aSpark2 		= [];

    this.mouse = {
		x : this.canvas.width * .5,
		y : this.canvas.height * .75,
	}
	//一旦鼠标移动,就更新this.mouse.x和this.mouse.y,因为设置了false,所以先进来的事件先处理
	this.canvas.addEventListener('mousemove', this.updateMouse.bind( this ), false);
}
Fire.prototype.updateMouse = function( e ){
	this.mouse.x = e.clientX;
	this.mouse.y = e.clientY;
}

第三步:

使用requestAnimationFrame使下一帧重新运行一遍run函数。为什么不用setInterval呢?因为内在运行机制会让它运行速度随机器性能变化而变化,导致时间控制不精确。而requestAnimationFrame使用系统时间,保证每秒执行60次。参考:https://www.cnblogs.com/xiaohuochai/p/5777186.html

bind()方法创建一个新的函数,在bind()被调用时,这个新函数的this被bind的第一个参数指定,其余的参数将作为新函数的参数供调用时使用。参考:https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Function/bind

Fire.prototype.run = function(){
	//重新新绘制火焰和火花
	this.update();
	this.draw();
    //稳定重绘画面
	requestAnimationFrame( this.run.bind( this ) );
}

第四步:

重新绘制一个火焰(实际上是红色的圆)和两个火花(实际上是小长方形)。若有火焰或火花的生命周期完了,那么就用删除它。否则继续更新它。

注意火焰火花原本被存储在数组里,所以删除用slice就好了。

Fire.prototype.update = function(){

	//绘制新的火焰(红色的圆)以及火花
	this.aFires.push( new Flame( this.mouse ) );
	this.aSpark.push( new Spark( this.mouse ) );
	this.aSpark2.push( new Spark( this.mouse ) );
   //之前元素,即新的火焰(红色的圆)以及火花的生命周期未完的话,就继续更新它,否则就删除它
	for (var i = this.aFires.length - 1; i >= 0; i--) {
		if( this.aFires[i].alive )
			this.aFires[i].update();
		else
			this.aFires.splice( i, 1 );
    }
    for (var i = this.aSpark.length - 1; i >= 0; i--) {
		if( this.aSpark[i].alive )
			this.aSpark[i].update();
		else
			this.aSpark.splice( i, 1 );
	}
    for (var i = this.aSpark2.length - 1; i >= 0; i--) {
		if( this.aSpark2[i].alive )
			this.aSpark2[i].update();
		else
			this.aSpark2.splice( i, 1 );
	}
}

第五步:

以火焰为粒子。部分注释在代码中。先使用构造函数确定火焰的各项参数。若火焰被更新,那么就更新它的坐标,生命周期,以及用生命周期计算颜色。这里的颜色使用的是HSLA颜色,参考:http://caibaojian.com/css3/values/color/hsla.htm

火花的构造参数和更新参数也是一样的。

var Flame = function( mouse ){

	//鼠标坐标
	this.cx = mouse.x;
	this.cy = mouse.y;
	
	//随机在鼠标周围产生
	this.x = rand( this.cx - 25, this.cx + 25);
	this.y = rand( this.cy - 5, this.cy + 5);
	
	//随机变量,横轴纵轴以及半径的变化
	this.vy = rand( 1, 3 );
	this.vx = rand( -1, 1 );
	this.r = rand( 20, 30 );
	
	//生命周期
	this.life = rand( 3, 6 );
	this.alive = true;
	//用于绘制火焰颜色
	this.c = {
		h : Math.floor( rand( 2, 40) ),
		s : 100,
		l : rand( 80, 100 ),
		a : 0,
		ta : rand( 0.8, 0.9 )
	}
}

Flame.prototype.update = function()
{
    //y坐标变化
	this.y -= this.vy;
	this.vy += 0.05;
   
	//x坐标变化
	this.x += this.vx;
	if( this.x < this.cx )
		this.vx += 0.1;
	else
		this.vx -= 0.1;
	
	//半径变化
	if(  this.r > 0 )
		this.r -= 0.1;
	if(  this.r <= 0 )
		this.r = 0;


    //计算生命周期,根据生命周期计算火焰颜色
	this.life -= 0.15;
	if( this.life <= 0 ){
        this.c.a -= 0.05;
		if( this.c.a <= 0 )
			this.alive = false;
	}else if( this.life > 0 &amp;&amp; this.c.a < this.c.ta ){
		this.c.a += .08;
	}

}

第六步:

canvas的主场,绘制背景,包括黑色背景,文字FIRE,以及一个跟随在火焰后的暗红色大圆。这个大圆大圆,更像是墙壁的上的投影,需要仔细一点才能发现。canvas参考https://www.w3school.com.cn/tags/html_ref_canvas.asp,自己一个函数一个函数慢慢去查才能加深印象。

注意globalCompositeOperation的参数soft-light和color-dodge似乎国内网站都没找到解释,只在英文mdn上看到了样例。参考:

https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/globalCompositeOperation

Fire.prototype.draw = function(){

	//绘制背景
	this.ctx.globalCompositeOperation = "source-over";
	this.ctx.fillStyle = "rgba( 15, 5, 2, 1 )";
	this.ctx.fillRect( 0, 0, window.innerWidth, window.innerHeight );
	
	//定义渐变颜色样式
	this.grd = this.ctx.createRadialGradient( this.mouse.x, this.mouse.y - 200,200,this.mouse.x, this.mouse.y - 100,0 );
	this.grd.addColorStop(0,"rgb( 15, 5, 2 )");
	this.grd.addColorStop(1,"rgb( 30, 10, 2 )");
	
	//绘制一个圆形,并使用颜色渐变样式。这个圆是一个暗红色的大圆
	//跟随在火焰后的大圆,更像是墙壁的上的投影,需要仔细一点才能发现
	this.ctx.beginPath();
	this.ctx.arc( this.mouse.x, this.mouse.y - 100, 200, 0, 2*Math.PI );
	this.ctx.fillStyle= this.grd;
	this.ctx.fill();
	
    //绘制文字Fire
	this.ctx.font = "15em Amatic SC";
	this.ctx.textAlign = "center";
	this.ctx.strokeStyle = "rgb(50, 20, 0)";
	this.ctx.fillStyle = "rgb(120, 10, 0)";
	this.ctx.lineWidth = 2;
	this.ctx.strokeText("Fire",this.canvas.width/2, this.canvas.height * .72 );
	this.ctx.fillText("Fire",this.canvas.width/2, this.canvas.height * .72 );	
	
	//绘制火焰
	this.ctx.globalCompositeOperation = "overlay";
	for (var i = this.aFires.length - 1; i >= 0; i--)this.aFires[i].draw( this.ctx );
	
	//绘制粒子
	this.ctx.globalCompositeOperation = "soft-light";
	for (var i = this.aSpark.length - 1; i >= 0; i--)
	if( ( i % 2 ) === 0 )
			this.aSpark[i].draw( this.ctx );

    //绘制粒子2
	this.ctx.globalCompositeOperation = "color-dodge";
	for (var i = this.aSpark2.length - 1; i >= 0; i--) this.aSpark2[i].draw( this.ctx );
}

最后一步:

最关键但也很简单的地方,就是真正的绘制火焰和火花啦。beginpath(),arc(),fillstyle()和fill()都是canvas的方法。慢慢查找资料吧。只是注意这儿的颜色用的是hsla颜色而不是rgba颜色哦。


Flame.prototype.draw = function( ctx ){

	ctx.beginPath();
	ctx.arc( this.x, this.y, this.r * 3, 0, 2*Math.PI );
	ctx.fillStyle = "hsla( " + this.c.h + ", " + this.c.s + "%, " + this.c.l + "%, " + (this.c.a/20) + ")";
	ctx.fill();

	ctx.beginPath();
	ctx.arc( this.x, this.y, this.r, 0, 2*Math.PI );
	ctx.fillStyle = "hsla( " + this.c.h + ", " + this.c.s + "%, " + this.c.l + "%, " + this.c.a + ")";
	ctx.fill();

}

完整源码:

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Canvas实现火焰跟随鼠标动画</title>

<style>
@import url(https://fonts.googleapis.com/css?family=Amatic+SC);
html, body {
	margin:0;
	padding:0;
	height: 100%;
}
</style>

</head>
<body>
<div style="text-align:center;clear:both;">
</div>
<canvas id="fire"></canvas>

<script>
var Fire  = function(){

	this.canvas 		= document.getElementById('fire');
	this.ctx 			= this.canvas.getContext('2d');
	this.canvas.height 	= window.innerHeight;
	this.canvas.width 	= window.innerWidth;

	this.aFires 		= [];
	this.aSpark 		= [];
	this.aSpark2 		= [];



	this.mouse = {
		x : this.canvas.width * .5,
		y : this.canvas.height * .75,
	}
	//一旦鼠标移动,就更新this.mouse.x和this.mouse.y,因为设置了false,所以先进来的事件先处理
	this.canvas.addEventListener('mousemove', this.updateMouse.bind( this ), false);

}
Fire.prototype.run = function(){
	//重新新绘制火焰和
	this.update();
	this.draw();

	//稳定重绘画面
	requestAnimationFrame( this.run.bind(this));

}
Fire.prototype.update = function(){

	//绘制新的火焰(红色的圆)以及火花
	this.aFires.push( new Flame( this.mouse ) );
	this.aSpark.push( new Spark( this.mouse ) );
	this.aSpark2.push( new Spark( this.mouse ) );



	//之前元素,即新的火焰(红色的圆)以及火花的生命周期未完的话,就继续更新它,否则就删除它
	for (var i = this.aFires.length - 1; i >= 0; i--) {
		if( this.aFires[i].alive )
			this.aFires[i].update();
		else
			this.aFires.splice( i, 1 );

	}

	for (var i = this.aSpark.length - 1; i >= 0; i--) {
		if( this.aSpark[i].alive )
			this.aSpark[i].update();
		else
			this.aSpark.splice( i, 1 );
	}


	for (var i = this.aSpark2.length - 1; i >= 0; i--) {
		if( this.aSpark2[i].alive )
			this.aSpark2[i].update();
		else
			this.aSpark2.splice( i, 1 );
	}

}

Fire.prototype.draw = function(){

	//绘制背景
	this.ctx.globalCompositeOperation = "source-over";
	this.ctx.fillStyle = "rgba( 15, 5, 2, 1 )";
	this.ctx.fillRect( 0, 0, window.innerWidth, window.innerHeight );
	
	//定义渐变颜色样式
	this.grd = this.ctx.createRadialGradient( this.mouse.x, this.mouse.y - 200,200,this.mouse.x, this.mouse.y - 100,0 );
	this.grd.addColorStop(0,"rgb( 15, 5, 2 )");
	this.grd.addColorStop(1,"rgb( 30, 10, 2 )");
	
	//绘制一个圆形,并使用颜色渐变样式。这个圆是一个暗红色的大圆
	//跟随在火焰后的大圆,更像是墙壁的上的投影,需要仔细一点才能发现
	this.ctx.beginPath();
	this.ctx.arc( this.mouse.x, this.mouse.y - 100, 200, 0, 2*Math.PI );
	this.ctx.fillStyle= this.grd;
	this.ctx.fill();
	
    //绘制文字Fire
	this.ctx.font = "15em Amatic SC";
	this.ctx.textAlign = "center";
	this.ctx.strokeStyle = "rgb(50, 20, 0)";
	this.ctx.fillStyle = "rgb(120, 10, 0)";
	this.ctx.lineWidth = 2;
	this.ctx.strokeText("Fire",this.canvas.width/2, this.canvas.height * .72 );
	this.ctx.fillText("Fire",this.canvas.width/2, this.canvas.height * .72 );	
	
	//绘制火焰
	this.ctx.globalCompositeOperation = "overlay";
	for (var i = this.aFires.length - 1; i >= 0; i--)this.aFires[i].draw( this.ctx );
	
	//绘制粒子
	this.ctx.globalCompositeOperation = "soft-light";
	for (var i = this.aSpark.length - 1; i >= 0; i--)
	if( ( i % 2 ) === 0 )
			this.aSpark[i].draw( this.ctx );

    //绘制粒子2
	this.ctx.globalCompositeOperation = "color-dodge";
	for (var i = this.aSpark2.length - 1; i >= 0; i--) this.aSpark2[i].draw( this.ctx );
}

Fire.prototype.updateMouse = function( e ){
	this.mouse.x = e.clientX;
	this.mouse.y = e.clientY;
}








var Flame = function( mouse ){

	//鼠标坐标
	this.cx = mouse.x;
	this.cy = mouse.y;
	
	//随机在鼠标周围产生
	this.x = rand( this.cx - 25, this.cx + 25);
	this.y = rand( this.cy - 5, this.cy + 5);
	
	//随机变量,横轴纵轴以及半径的变化
	this.vy = rand( 1, 3 );
	this.vx = rand( -1, 1 );
	this.r = rand( 20, 30 );
	
	//生命周期
	this.life = rand( 3, 6 );
	this.alive = true;
	//用于绘制火焰颜色
	this.c = {
		h : Math.floor( rand( 2, 40) ),
		s : 100,
		l : rand( 80, 100 ),
		a : 0,
		ta : rand( 0.8, 0.9 )
	}
}

Flame.prototype.update = function()
{
    //y坐标变化
	this.y -= this.vy;
	this.vy += 0.05;
   
	//x坐标变化
	this.x += this.vx;
	if( this.x < this.cx )
		this.vx += 0.1;
	else
		this.vx -= 0.1;
	
	//半径变化
	if(  this.r > 0 )
		this.r -= 0.1;
	if(  this.r <= 0 )
		this.r = 0;


    //计算生命周期,根据生命周期计算火焰颜色
	this.life -= 0.15;
	if( this.life <= 0 ){
        this.c.a -= 0.05;
		if( this.c.a <= 0 )
			this.alive = false;
	}else if( this.life > 0 &amp;&amp; this.c.a < this.c.ta ){
		this.c.a += .08;
	}

}
Flame.prototype.draw = function( ctx ){

	ctx.beginPath();
	ctx.arc( this.x, this.y, this.r * 3, 0, 2*Math.PI );
	ctx.fillStyle = "hsla( " + this.c.h + ", " + this.c.s + "%, " + this.c.l + "%, " + (this.c.a/20) + ")";
	ctx.fill();

	ctx.beginPath();
	ctx.arc( this.x, this.y, this.r, 0, 2*Math.PI );
	ctx.fillStyle = "hsla( " + this.c.h + ", " + this.c.s + "%, " + this.c.l + "%, " + this.c.a + ")";
	ctx.fill();

}








var Spark = function( mouse ){

	this.cx = mouse.x;
	this.cy = mouse.y;
	this.x = rand( this.cx -40, this.cx + 40);
	this.y = rand( this.cy, this.cy + 5);
	this.lx = this.x;
	this.ly = this.y;
	this.vy = rand( 1, 3 );
	this.vx = rand( -4, 4 );
	this.r = rand( 0, 1 );
	this.life = rand( 4, 5 );
	this.alive = true;
	this.c = {

		h : Math.floor( rand( 2, 40) ),
		s : 100,
		l : rand( 40, 100 ),
		a : rand( 0.8, 0.9 )

	}

}
Spark.prototype.update = function()
{

	this.lx = this.x;
	this.ly = this.y;

	this.y -= this.vy;
	this.x += this.vx;

	if( this.x < this.cx )
		this.vx += 0.2;
	else
		this.vx -= 0.2;

	this.vy += 0.08;
	this.life -= 0.1;
	if( this.life <= 0 ){
		this.c.a -= 0.05;
		if( this.c.a <= 0 )
			this.alive = false;
	}

}
Spark.prototype.draw = function( ctx ){

	ctx.beginPath();
	ctx.moveTo( this.lx , this.ly);
	ctx.lineTo( this.x, this.y);
	ctx.strokeStyle = "hsla( " + this.c.h + ", " + this.c.s + "%, " + this.c.l + "%, " + (this.c.a / 2) + ")";
	ctx.lineWidth = this.r * 2;
	ctx.lineCap = 'round';
	ctx.stroke();
	ctx.closePath();

	ctx.beginPath();
	ctx.moveTo( this.lx , this.ly);
	ctx.lineTo( this.x, this.y);
	ctx.strokeStyle = "hsla( " + this.c.h + ", " + this.c.s + "%, " + this.c.l + "%, " + this.c.a + ")";
	ctx.lineWidth = this.r;
	ctx.stroke();
	ctx.closePath();

}

rand = function( min, max ){ return Math.random() * ( max - min) + min; };
onresize = function () { oCanvas.canvas.width = window.innerWidth; oCanvas.canvas.height = window.innerHeight; };



var oCanvas;
init = function()
{

	oCanvas = new Fire();
	oCanvas.run();
}
window.onload = init;
</script>

</body>
</html>

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