Flying memes

We Love Shadows! A CSS3 and Javascript based light source

CSS3 has gradients and CSS3 has shadows, so why don’t try to use both to simulate a light source ? That is the basic idea behind this project. I’ve set-up a small demo which let you use the mouse to direct a light source over a text and observe its shadow change according to light position.

To simulate the light behavior I used a CSS3 gradient on the body background and a text-shadow property on the text. Both of these css3 attributes are then¬†dynamically¬†changed upon the user’s mouse move.

Here’s the snippet of the JQuery-flavored¬†javascript I used:

$(document).ready(function() {
    $('body').mousemove(function(event) {
        $('#instructions').hide();

        // compute the center of the page and the distance between the center and the mouse
        // coordinates
        cx = Math.ceil($('body').width()  / 2);
        cy = Math.ceil($('body').height() / 2);
        dx = event.pageX - cx;
        dy = event.pageY - cy;

        // introducing a little parallax for the biggest light cone
        x0 = Math.ceil(cx - (dx * 0.2));
        y0 = Math.ceil(cy - (dy * 0.2));
        x1 = event.pageX;
        y1 = event.pageY;
        r0 = 300;
        r1 = 10;

        // another parallax for the text shadow
        sx = -dx * 0.03;
        sy = -dy * 0.03;

        // blur the shadow depending upon its distance
        b  =  (Math.abs(sx) + Math.abs(sy)) * 0.2;

        // simulate the light
        $('body').css('background-image', "-webkit-gradient(radial, " + x0 +" " + y0 +", "+ r0 +", "+ x1 +" "+ y1 +", "+ r1 +", from(#575757), to(#FFFFFF))");

        // simulate the shadow
        $('h1').css('text-shadow', "#444 "+ sx +"px "+ sy + "px " + b + "px");
    });
});

Here’s an image took from the demo, the whole page source code is available on my github account as a gist:

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