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html5网页特效-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

笔记:

google字体

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。

 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。

并用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。

web前端开发学习Q-q-u-n:784783012 ,分享学习的方法和需要注意的小细节,不停更新最新的教程和学习方法
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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

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 && 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。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。

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.fill15em 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:

web前端开发学习Q-q-u-n:784783012 ,分享学习的方法和需要注意的小细节,不停更新最新的教程和学习方法
(学习工具,详细的前端项目实战教程,PDF)




Canvas实现火焰跟随鼠标动画










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.fill15em 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 && 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;



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