MAKING 3D MODELS of Caguana's Petroglyphs

by Alicia P. Gregory, freelance science writer

IN THE SHADOW OF PUERTO RICO'S CENTRAL MOUNTAIN range and under clouds threatening rain, University of Kentucky students and computer scientist Brent Seales, Ph.D., set up a make-shift tent and unload USB cables, digital cameras, a laptop, and laser.

This technology is in sharp contrast to the setting. The Caguana Indian Ceremonial Park, in Utuado, dates back to 1200 A.D. Inside the park is a flat, gravel field bounded by upright stones, twenty-one of them carved with figures.

The mission of the UK team, as part of a $1 million National Science Foundation funded project with the University of Puerto Rico, Río Piedras, and the Institute of Puerto Rican Culture (ICP by its Spanish acronym), is to preserve the eroding petroglyphs by scanning them, reconstructing them as 3-D models, and displaying the models at the ICP in Ponce and at the UPR, RP campus. The collaborative project focuses on taking physical collections–paintings, sculptures, and petroglyphs–and turning them into a digital library. Visitors to the ICP in Ponce will be able to select artifacts and inspect them in a "virtual" display room.

And visitors to UPR, RP's College of Natural Sciences' Néstor M. Rodríguez Library, can be immersed in wall-sized images in a room dedicated to displaying these 3-D models. Herman Acuña, Ph.D., a professor of computer science at UPR, RP, and Seales installed a computer system consisting of projectors, computers, a camera, and a server to create high-resolution pictures in the room; and UPR, RP undergraduates working with a UK graduate student spent October through December of 2004 setting up the 2-D and 3-D data.

"We laid the groundwork for the project about three years ago. Together with the University of Kentucky, we started to digitize works of art. The next step was to digitize the petroglyphs. It wasn't easy because it rained a lot. Then the UK team returned and it rained again, but they still managed to take pictures, despite the rain. Now we want to project these digital pictures on a wall in the UPR library and on a wall in a room at the Institute," says Acuña. The digitized sculptures and petroglyphs will be projected in 3-D and will rotate to allow the visitors to see all sides. The digitized paintings will be projected in 2-D, and they will be larger than life.

UK graduate students Jess Muetterties and Jesus Cabán (formerly a UPR student) look at the 3-D model of the fertility goddess projected in an immersive viewing room.

Seales and his UK team have fully digitized seven of the 21 petroglyphs that they were able to photograph in the wet and muddy park. They collected this data with a laser and four cameras to capture 3-D shape, and two high-resolution cameras to capture photographic texture. "The laser shoots a line that the camera sees," Seales explains. "The geometry that you triangulate between the camera and the laser gives you the exact distance of that point away from the camera. So for every point on that laser beam, you can get an actual depth point. You put all of those points together, and you have the surface shape."

The UK team took this data back to Lexington, Kentucky, and spent several months constructing the 3-D models with a software package called Geomagic. "These models are photo-quality because we 'paste' a photograph on the right place on top of the shape. That's called texturing. We can turn that texture off and see just the shape. When you move the light source around–think of it like a flashlight–the shadows change and reveal parts of the carving you couldn't see even if you were in front of the actual stone," says Seales.

UK Team: Brent Seales, Peyton Fouts, Jess Muetterties,
Holly Putnam, Jesús Cabán, and Philip Putnam

"Of all our venues, Caguana is the custodian of our most ancient cultural heritage," says Adlín Ríos Rigau, former director of the museum and parks division of the ICP.

"Caguana is one of the most important archeological sites on the island because it presents, in all its complexity, the Taíno communities that inhabited Puerto Rico at the time of the Spanish arrival." Caguana receives 40,000 visitors each year.

In addition to digitally displaying the petroglyphs, the ICP in Ponce will make available works of art that were previously unavailable to the public because of lack of display space. "There were many works of art at the Institute that were not displayed–they were just sitting in a room. They were very well taken care of by the Institute, stored in air-conditioned rooms, but still the public wasn't able see them. Now the public will be given the opportunity to view them, and they'll be preserved in a digital format," says Acuña.

José Ramón Villalón (UPR), Professor Herman Acuña (UPR),
Daniel Olson (UK) and Giovany Vega (UPR)

www.icp.gobierno.pr