Emulating Windows 8 Tilt Effect

When you click on a tile from the start screen on Windows 8, there is a nice effect where the tile "tilts" backwards towards the pointer or touch location. See below for an example:

Taken from IEBlog
The tilt direction appears be to based on the mouse or touch location. The image above was taken when the click was towards the right side of the live tile. The regions of the image that dictate the direction of the tilt is dictated roughly by the below guidelines:

Regions that determine direction of tilt.

The center region simply causes the tile to be depressed as an HTML button or other similar icon. The first step towards emulating this behavior is to determine the direction of the tilt. Once the direction is chose, we must apply the correct CSS3 3D transform to the tile.

Let's first define our points of interest relative to our object, which will be defined by its top-left coordinate (left, top) with width width and height height.
1. Center defined by rectangle:
(left+(width/2)-(.1*left), top+(height/2)-(.1*top)) width .2*width height .2*height.
2. Descending line defined by point (left, top) and slope (-height / width):
ytop = (-height / width) * (x - left)
3. Ascending line defined by point (left, top+height) and slope (heigh,width):
y - (top + height) = (height / width) * (x - left)

Now that we've defined our points of interest, we can take the incoming click and determine which direction the tilt is. The below code will install an event handler for the mouse down event for ever element with class "tilt".
        $(".tilt").each(function () {
            $(this).mousedown(function (event) {
                // Does the click reside in the center of the object 
                if (event.pageX > $(this).offset().left + ($(this).outerWidth() / 2) - (0.1 * $(this).outerWidth()) &&
                        event.pageX < $(this).offset().left + ($(this).outerWidth() / 2) + (0.1 * $(this).outerWidth()) &&
                        event.pageY > $(this).offset().top + ($(this).outerHeight() / 2) - (0.1 * $(this).outerHeight()) &&
                        event.pageY < $(this).offset().top + ($(this).outerHeight() / 2) + (0.1 * $(this).outerHeight())) {
                    $(this).css("transform", "perspective(500px) translateZ(-15px)");
                } else {
                    var slope = $(this).outerHeight() / $(this).outerWidth(),
                        descendingY = (slope * (event.pageX - $(this).offset().left)) + $(this).offset().top,
                        ascendingY = (-slope * (event.pageX - $(this).offset().left)) + $(this).offset().top + $(this).outerHeight();

                    if (event.pageY < descendingY) {
                        if (event.pageY < ascendingY) {
                            // top region
                            $(this).css("transform", "perspective(500px) rotateX(8deg)");
                        } else {
                            // right region
                            $(this).css("transform", "perspective(500px) rotateY(8deg)");
                        }
                    } else {
                        if (event.pageY > ascendingY) {
                            // bottom region
                            $(this).css("transform", "perspective(500px) rotateX(-8deg)");
                        } else {
                            // left region
                            $(this).css("transform", "perspective(500px) rotateY(-8deg)");
                        }
                    }
                }
            });

            $(this).mouseup(function (event) {
                $(this).css("transform", "");
            });
        });

Here is a below working example. Click the image to see the tilt effect:


Let me know if you find any particular issues with any browsers or have any comments below. I also should plug the useful tools used to help with this code:

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