The Giant Who Walks Amongst Us

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That visual slip confuses the brain, making a child feel off balance, mirroring the effects of alcohol consumption, Dempski claims. The user would lose the ability to differentiate between what she's really seeing and what's being injected into a scene via the lens.

However, experiments with these head-mounted displays has paved the way for more practical, more commercially viable AR devices such as Personal Digital Assistants (PDA) and projectors.

A PDA was used to view Magic Book, demonstrated at SIGGRAPH 2000 by a team of researchers, including Billinghurst, then with the University of Washington's Human Interface Technology Laboratory.

But this book's images -- of boxy buildings and a stiff, humanesque figure -- weren't very sophisticated or capable of much interaction. Instead, the 3-D visuals were like "pop-up drawings on paper," says Ulrich Neumann, professor of computer science at the University of Southern California .

The real breakthrough for the mobile AR will come when books are loaded with "trigger symbols," or markers, that a PDA could track and then turn into organic images leaping off the page. Doing so, though, isn't practical and is a visual turn off to readers; the markers look like barcodes, says Ramesh Raskar, a senior research scientist with Mitsubishi's Electric Research Labs (MERL). (Ulrich, Billinghurst and others are working on algorithms for tracking to reduce the barcode look.)

That has led researchers look at alternatives such as radio frequency identification tags (RFIDs) and touch sensors in lieu of visible computers and their components.

"The point is to hide the computer," Raskar says. "The technology should be entirely transparent."

Building a Better Virtual Story

Spatial augmented reality makes this possible. Instead of merely overlaying images on top of objects within a reader's view, a projector makes objects and images appear to blend into your very world -- in front, to the side and behind you.

The advantage of this technology's use in interactive storybooks is the reader can create non-linear and event-driven stories.

Raskar says a child no longer would have to read his book page by page, and any physical action of his could change the action in and plot of the story.

"To open a book and see this animation happen is counter to anyone's experience," Neumann says. "This is not to replace the imagination, but to help it along a bit" in the same way film adds dimensions to stories.

But Raskar says the future of spatial AR technology in books is limited. So AR for storytelling may leap completely off the page.

Steven Feiner, computer science professor, and his colleagues with Columbia University's Computer Graphics and User Interface Lab and in collaboration with its Graduate School of Journalism, have turned documentary films into more interactive and educational tools.

In one of the lab's "situated documentaries" about Columbia University's system of underground tunnels, a viewer hears narration and sees both the campus and flag-like markers that indicate where portions of the story are located, Feiner explains.