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Why oh why is this so slow? I have made an isometric grid of cubes with css3 that bobs up and down on mouseover. It works great on Firefox with a grid size less than about 12 and with Chrome works pretty good under about 18. I have a decent video card and CPU and the thing that is bugging me is why it is so slow to animate just one cube's animations if I make sure I only mouseover one cube. Does my JavaScript need optimisation or is this just to be expected from the current implementation of browser CSS3 and JavaScript engines? Full test case below includes slider to change grid size on the fly, can either download for yourself or visit this jsfiddle version graciously provided by Doug.

<html>
    <head>
        <style type="text/css">
            body
            {
                background: black;
            }

            .cube
            {
                position: relative;
            }

            .cube .rightFace, .cube .leftFace
            {
                height: 25px; width: 10px; padding: 5px;
            }

            .leftFace
            {
                position: absolute;

                -webkit-transform: skew(0deg, 30deg);
                -moz-transform: skew(0deg, 30deg);
                -o-transform: skew(0deg, 30deg);

                -moz-box-shadow: rgba(0, 0, 0, 0.4) 1px 2px 10px;
                -webkit-box-shadow: rgba(0, 0, 0, 0.4) 1px 2px 10px;
                -o-box-shadow: rgba(0, 0, 0, 0.4) 1px 2px 10px;
                box-shadow: rgba(0, 0, 0, 0.4) 1px 2px 10px;

                border: 1px solid black;
            }

            .rightFace
            {
                -webkit-transform: skew(0deg, -30deg);
                -moz-transform: skew(0deg, -30deg);
                -o-transform: skew(0deg, -30deg);

                position: absolute;
                left: 19.5px;

                border: 1px solid black;
            }

            .topFace div
            {    
                width: 19px;
                height: 19px;


                border: 1px solid black;

                -webkit-transform: skew(0deg, -30deg) scale(1, 1.16);
                -moz-transform: skew(0deg, -30deg) scale(1, 1.16);
                -o-transform: skew(0deg, -30deg) scale(1, 1.16);
            }

            .topFace
            {
                position: absolute;

                left: 10.25px;
                top: -16.5px;

                -webkit-transform: rotate(60deg);
                -moz-transform: rotate(60deg);
                -o-transform: rotate(60deg);
            }

            #slider
            {
                width: 200px;
                margin: 0 auto;
            }
        </style>
        <link type="text/css" rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/themes/base/jquery-ui.css" />
        <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>
        <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8/jquery-ui.min.js"></script>
        <script type="text/javascript">
            function refreshCubes()
            {
                $('.box').empty();
                var x = $("#slider").slider("value");
                var initialTop = 50;
                var initialLeft = 450;

                for(var i = 1; i < x; i++)
                {
                    for(var j = 1; j < x; j++)
                    {
                        var cube = $('<div class="cube"><div class="topFace"><div></div></div><div class="leftFace"></div><div class="rightFace"></div></div>');

                        cube.css(
                        {
                            left : initialLeft + (20 * i) + (-19 * j) + 'px',
                            top : initialTop + (11 * i) + (11 * j) + 'px'
                        });

                        cube.find('.topFace div').css('background', 'rgb(100,' + Math.ceil(255 - 16 * i) + ',' + Math.ceil(255 - 16 * j) + ')');
                        cube.find('.rightFace').css('background', 'rgb(35,' + Math.ceil(190 - 16 * i) + ',' + Math.ceil(190 - 16 * j) + ')');
                        cube.find('.leftFace').css('background', 'rgb(35,' + Math.ceil(190 - 16 * i) + ',' + Math.ceil(190 - 16 * j) + ')');
                        cube.children('div').css('opacity', '.9');

                        cube.hover(function()
                        {
                            $(this).animate({top: '-=25px'}, 400, 'easeInCubic');

                        }, function()
                        {
                            $(this).animate({top: '+=25px'}, 400, 'easeOutBounce');
                        });

                        $('.box').append(cube);
                    }
                }
            }

            $(document).ready(function()
            {    
                $('#slider').slider(
                {
                    value: 9,
                    max: 30,
                    min: 2,
                    slide: refreshCubes,
                    change: refreshCubes
                });

                refreshCubes();
            });
        </script>
    </head>
    <body>
        <div id="slider"></div>
        <div class="box"></div>
    </body>
</html>
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3
  • That's interesting. Its pretty slow with a bigger grid size. It must be because it is software rendering??? Have you tried it in IE9+? IE9 seems to have hardware acceleration for DOM manipulation. I'm reinstalling IE9 right now...
    – trusktr
    Commented Nov 5, 2011 at 5:15
  • I grabbed IE9 and Chrome as soon as I noticed it was slower with the bigger grid but not much changed
    – AmbrosiaDevelopments
    Commented Nov 5, 2011 at 6:06
  • I wonder if hardcoding a series of animations that would simulate a mouse moving over the large grid (instead of using the mouseover events) would still be too slow.
    – AmbrosiaDevelopments
    Commented Nov 5, 2011 at 6:15

3 Answers 3

Reset to default
9

This one is faster: http://jsfiddle.net/JycdN/1/

I optimized the jQuery code itself. Also, its a bad idea to animate a "+=25px" style CSS value because each time you do that you are forcing the browser to make extra CSS calculations on top of the animation calculations. Instead of doing that, you might as well just use plain CSS3 animations. Check this out: http://matthewlein.com/ceaser/

Its better for animate() to have a static value (in this case, the original and raised positions which i've stored for each cube in the data- attributes) so the only calculations being done are the ones by the javascript interpreter itself.

The live() method automatically adds the events to the cubes whenever they are recreated, so there's no need to set the events inside the refreshcubes function. Also, James Montagne pointed out that using the live() method makes the whole thing behave like Daniel described in his answer (which is faster). EDIT: I've made it even faster by using the on() method instead of live(). The event context for hovering is now on each cube instead of on the whole document. See this question for details: How does jQuery's new on() method compare to the live() method in performance?.

Wherever possible, make one single jquery object and reference to it with a variable, that way you don't recreate a new object every time.

Overall, I noticed quite an increase in performance, but its still slower than I'd imagine capable. Maybe the CSS transforms are re-calculated every time the cubes are moved (even by a pixel).

EDIT: As addedlovely suggested, modifying the jQuery.fx.interval helped make it a little faster.

I think you'll have more luck drawing the cubes in 2D canvas or with 3D webGL canvas.

Try using three.js or processing.js to draw the cubes and animate them.

EDIT: I've made it even faster using hardware-accelerated CSS3 animations in Google Chrome (other browsers are still developing these CSS3 features so it only works in CHrome for now): http://jsfiddle.net/trusktr/JycdN/35/

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14
  • Interesting point about the live() method. I will definitely implement that. Thanks for the animation optimisation pointer. I have one written in 2D Canvas but it also slowed down considerably after reaching grid sizes above 15. Haven't dabbled in 3D webGL or used three.js or processing.js yet but might soon.
    – AmbrosiaDevelopments
    Commented Nov 5, 2011 at 6:09
  • The cool thing about WebGL will be that everything will run smooth with the video acceleration. :D
    – trusktr
    Commented Nov 5, 2011 at 6:19
  • I just tested it in IE9. Its pretty bad!
    – trusktr
    Commented Nov 5, 2011 at 6:21
  • Just tried removing the mouseover event handlers and added CSS3 transitions/transformations(translateY) and its even slower or less responsive on the hovers anyway.
    – AmbrosiaDevelopments
    Commented Nov 5, 2011 at 7:50
  • 1
    Hey, check it out, I made it better: jsfiddle.net/trusktr/JycdN ..Now the animations don't repeat over and over for each time the mouse enters and leaves. However, the whole animations still animate entirely. You might have noticed that simply adding .stop() before .animate() caused the animations to stop and the boxes wouldn't pop out all the way. This is what I mean by that: jsfiddle.net/trusktr/JycdN/16 ...I think that's pretty much as fast as its going to get.
    – trusktr
    Commented Nov 9, 2011 at 3:05
3

You have n^2 listeners, honestly surprised things work as well as they do. Jquery does not have enough information to optimize the algorithm, but we do. Instead of caring about where the mouse is n^2 times we actually only need to check once.

Add a listener to the entire board. On call calculate which cell is being hovered over and animate that one. Keep a list of cells in the 'on' state and calculate if the mouse is still hovering over them, if not animate them to their original state and remove them from the list.

Now instead of n^2 operations a frame you have 1. More, but much faster, code and the same functionality. Yes jquery is awesome and having to do this yourself is a pity. Keep in mind though that jquery is designed for those 10s of listeners which an average site will use, not for 100s or 1000s.

@trusktr: It is indeed faster but still many times slower than necessary.

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4
  • That's interesting. So are you saying that every time you move the mouse all the hover events are being activated, but not necessarily acted upon? I never thought it was like that. Also, can you fork Ambrosia's or My fiddle and implement your idea?
    – trusktr
    Commented Nov 5, 2011 at 5:39
  • live or even better delegate works very similar to what you have described. It only attaches one listener and then determines the matching element within.
    – James Montagne
    Commented Nov 5, 2011 at 5:39
  • @James Montagne If that's the case, then that might explain why my answer was a bit faster.
    – trusktr
    Commented Nov 5, 2011 at 5:41
  • Interesting, I wouldn't have thought the browser would have such a hard time with the event handlers as you say. I wouldn't mind a jsfiddle fork if you have the time but I will probably reread your answer and play around with it later tonight or tomorrow if I have time.
    – AmbrosiaDevelopments
    Commented Nov 5, 2011 at 6:11
3

In addition to the excellent points above you may want to check out the Jquery fx Interval.

http://api.jquery.com/jQuery.fx.interval/

By default the animate intervals are set to 13ms, about 76 frames a second. Seems silly, so setting this down to a more 20 frames a seconds (50ms), will give you a performance boost.

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1
  • I tested what u said, but it didn't have any obvious effects. In my code I just move a large image by 2000px to left.
    – Ata Iravani
    Commented Sep 10, 2012 at 6:53

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