I love how easy it is to create reveal animations for objects, but I was wondering if there's a way to do a reverse reveal.

For example, when scrolling down a page, an object reveals near the bottom edge of the site. Then, when it's about to leave the visible area near the top of the page, the object performs a counter reveal. This effect would be useful for fades (fade-in/fade-out) as well as motion effects (fly-in/fly-out).

Has anyone created something like this? I thought, perhaps it could be accomplished by placing trigger objects at certain points along the outside of the visible area of the site, but there aren't any pre-built effects for reverse actions in the animation dialog.

Any help would be greatly appreciated.