Cool Animated Fire Effects with CSS3 and jQuery

This effect has been created with some jQuery for setting different CSS3 text-shadow’s in a div. You can check the demo code to see how it’s done. Basically, the Javascript function creates 3 text-shadows (white, yellow and red) with coprime “cycle durations” so the effect looks more random even though it’s totally deterministic.

Each shadow moves in the Y axis with a linear function and in the X axis with a cosine function. Pretty simple, but effective.

The CSS

#onfire{
      height:auto;
      padding-top:3em;
      font-size: 42px;
      font-weight: bold;
      text-align: center;
      color:brown;
}

The jQuery

<script type="text/javascript">
var step = 1;
function nextShadow(){
	$('#onfire span').each(function(){
	    y = parseFloat($(this).attr("y_pos"));
	    y += step + Math.random()*3;
	    $(this).attr("y_pos", y);
	    shaking = Math.random();
	    shadow1 = "0px 0px "+(y%5)+"px white";
	    shadow2 = shaking*24/y*Math.cos(y/5)*15+"px -"+(shaking*4/y+(y%17))+"px "+(shaking+(y%17))+"px red";
	    shadow3 = shaking*24/y*Math.cos(y/7)*15+"px -"+(shaking*4/y+(y%31))+"px "+(shaking+(y%31))+"px #993";
	    shadow4 = shaking*24/y*Math.cos(y/13)*15+"px -"+(shaking*4/y+(y%41))+"px "+(shaking+(y%41))+"px yellow";
	    $(this).css("text-shadow", shadow2+", "+shadow1+", "+shadow4+", "+shadow3);
	});
}
$(function(){
    $('#onfire span').each(function(){$(this).attr("y_pos","0");});
   setInterval(nextShadow, 50); 
});
</script>

Update:

I’ve added some randomisation to the algorithm, as well as an individual animation to each of the letters (which, as a drawback, makes the effect run less smooth). I’ve also added a fourth shadow in dark yellow. You can freely use the code by keeping the mention to this site on it.

Thanks for reading and looking forward to read your thoughts!