Friday, April 16, 1999

In Digitizing 'David,' a Stanford Professor Tries to Carve His Own Niche By CAROLYN J. MOONEY Florence It's so quiet inside the Galleria dell'Accademia once the tourists leave. Michelangelo's 17-foot-tall "David" stands alone in an alcove at the rear of the empty main hall. His muscles and sinews ripple, as if they sprang from flesh rather than marble. A night guard's footsteps echo across the stone floor, but it is the graceful, nude "David" -- the biblical hero who slew Goliath, the masterpiece everyone comes here to see -- that seems to keep watch over the statuary and triptychs. Digital Michelangelo Project Before scanning "David," researchers constructed a gantry to hold the laser scanner. Marc Levoy arrives a few minutes after the museum closes. An associate professor of computer science at Stanford University, he has grown accustomed to nocturnal visits with "David." For several weeks, he and a research team have been working through the night to produce a digital, three-dimensional computer model of the famous sculpture. They scramble now to set up their computer terminals and equipment, cordoned off in a corner. It takes two people to move a large laser scanner mounted on a 20-foot gantry, which is used to sweep across the statue repeatedly, from hundreds of angles. The resulting digital data will be converted into a three-dimensional model, bit by bit, until the entire sculpture has been re-created. The computer archive, which would probably be used by scholars and museums (the data sets are too big to download over the Internet), would allow viewers to rotate the sculpture on a computer screen, look at it from different angles, and zoom in on details. They might even be able to animate it. Mr. Levoy has two degrees in architecture, a doctorate in computer science, and several years of experience as director of computer animation at Hanna-Barbera (producers of The Flintstones and other cartoons). He is quick to tell you that he'd like to make a splash in the worlds of art history and computer science. So he aimed for a high-profile artist in a city where Stanford had a study center he could use as a base during his sabbatical. "One reason for choosing Michelangelo was, I knew we'd hit a lot of art historians, and museums would take note. We'd like to see other museums take on this kind of work." The scanning of "David" is part of a project to produce a computer archive of Michelangelo's most important statues. Mr. Levoy's team plans to include four unfinished sculptures of slaves that are also housed at the Accademia, the sculptures and architecture of the Medici Chapel here, and the "Pietà" and "Moses" in Rome. A few museums have already digitized statues, but none has scanned such a large object at such fine resolution, Mr. Levoy says. His custom-made equipment scans with a quarter-millimeter precision -- fine enough to see the artist's chisel marks. As part of the $1.5-million project, the team also plans to digitally reassemble an ancient mosaic map of Rome and to scan the Vatican's "Laocoön," an ancient sculpture that depicts the priest Laocoön and his two sons being strangled by serpents. The Interval Research Corporation, a technology laboratory in Palo Alto, Cal., and the Allen Foundation for the Arts are paying the bill. (Paul Allen, co-founder of Microsoft, helped establish the lab and foundation.) The project has been well documented on the Internet. Its World-Wide Web site contains many links, including one to the sculptures of Mr. Levoy's mother (she's an artist) and another to a field trip that he led to the marble-producing town of Pietrasanta, in the mountains west of Florence. The road that Michelangelo designed to bring marble from the area remains. Michelangelo Buonarroti was still in his 20s when he finished carving "David," in 1504. Commissioned by the city as a symbol of independence, it stood in the Piazza della Signoria until 1873, when it was moved to the Accademia. A copy now stands in the piazza, but it is the original that tourists stand in line to see. Cristina Acidini Luchinat, an inspector with Italy's ministry of culture, doesn't expect that to change. Critics who have accused the museum of trying to "clone" the precious sculpture are missing the point, she says. Among other things, digital technology could help track the condition of artworks. "We're excited about it," she says. Kathleen Weil-Garris Brandt, a New York University art historian who is in Florence preparing an exhibition of Michelangelo's early work, is interested -- but guarded. "The computer image of three-dimensional objects has an authority and status and reality that is false," she says. "The computer people I have known have tended to have an unexamined faith in the objectivity of what they're doing. But seeing is a complex act." For example: "The way we see the 'David' is entirely conditioned to the size of our bodies in relation to his." "Listen," says Jack Wasserman, a professor emeritus of art history at Temple University, "anyone who relies on photographs or digital images alone without looking at the original is a fool. These are all aids to seeing, and they're all useful." Seeing a digital image is like listening to a Beethoven symphony on a CD rather than in a concert hall, he explains. "What do you miss? The nuances, the tones of the instruments, the emotional quality. It's the same with a work of art." Nonetheless, Mr. Wasserman was so impressed by the technology that last year he worked with an I.B.M. team to scan Michelangelo's second "Pietà," in Florence. (He had also approached Mr. Levoy about doing the project.) The "Pietà" in the Vatican, carved by a young Michelangelo, depicts Mary tenderly holding her dead son. An elderly Michelangelo carved the unfinished Florentine "Pietà," which he planned to use for his own tomb but intentionally ruined. Christ's broken body is held up by Mary Magdalene, aided by Nicodemus and the Virgin Mary. Digital Michelangelo Project The red light of a laser beams scans the statue's nose. The digital model let Mr. Wasserman see how the sculpture was repaired. It also made it clear that Michelangelo, a master at tricks of proportion, meant for the sculpture to be placed higher up, probably on an altar. "The digital image radically changes what you see. The composition becomes more complete." At the Accademia, the first shift of scanning is well under way; the second will start after midnight. The 22-member team includes two professors, a research associate, graduate students, and undergraduates enrolled in a field course Mr. Levoy teaches. Most of them work full time. They take turns scanning, processing data at a laboratory housed in an old palazzo here, and catching up on sleep. The scanning works like this: The laser casts a thin stripe of red light onto the sculpture as a video camera is trained on the sculpture from one side. The object's shape can be computed by analyzing the changing shape of the stripe as it sweeps across the surface. The resulting data take the form of a grid of points in three-dimensional space, which are then connected to form a mesh of millions of tiny triangles. Images from repeated scans are combined into a seamless mesh, a step that uses an algorithm developed by the project's other professor, Brian Curless, a computer scientist at the University of Washington. Often, several scans are needed to get into crevices, such as the lips. Each segment of the sculpture is then scanned a second time, by white light, to record color. One of the most striking features of "David" is its anatomical precision. The neck bulges. The biceps flex. The hair nestles in soft clusters. The eyes focus intently. (Actually, they don't, as Mr. Levoy will explain.) Michelangelo captured such a range of expression -- strength and sweetness, tension and grace. Mr. Levoy will never again see "David" with the wonder of the first-time viewer. Still, he constantly sees new things. "Notice how each eyeball gazes in a different direction," he says. You see it only when you look at the statue head-on, which the average visitor can't do because of the way the sculpture is displayed. He believes that the artist meant for the statue to be viewed in profile. Digital Michelangelo Project A sample digitized image of the head of "David." "And those furrowed brows," he says. "Your brows would never protrude like that, but when seen from down below, it looks right. Michelangelo wasn't just a good carver, but a clever showman." Because of the security system, team members can't come and go as they please; once they enter, they're here until the second shift arrives. Alana Chan, an undergraduate who is scanning one of the slave statues, doesn't mind. "It's exciting to be so close to Michelangelo," she says. There are worse ways you could spend an evening.