Michelangelo Reborn Through Full-Size Virtual 3-D Sculptures

Through the magic of advanced computer graphics, art lovers soon may be able to examine highly realistic, 3-D images of the statues of Michelangelo on their personal computers or on display screens at public art museums. Under development by researchers at Stanford University (Stanford, CA), the Digital Michelangelo Project may soon make it possible to view a sculpture from different angles, zoom in on details as small as chisel marks, change lighting conditions to see how they affect a statue's appearance and animate classic art figures.

The Digital Michelangelo Project is an ambitious effort to create the first authoritative 3-D computer archive of the 15th-century Italian artist's most famous sculptures. The project will produce some of the largest 3-D computer models ever made and will combine color and shape information at a level of detail never before attempted. The project also may set a new standard for computer representations of 3-D physical objects.

Through the Digital Michelangelo Project, virtual copies of Michelangelo's statues will be available for appreciation and study around the world.

The Stanford research team conducting the project is working closely with officials from a number of Italian museums and institutions in Florence, Rome and the Vatican who have given them access to the priceless art treasures. In mid-January 1999, the researchers intend to begin scanning Michelangelo's sculptures in the Gallerie dell'Accademia in Florence, including The Unfinished Slaves and The David. In February 1999, the team is scheduled to move its work to the Medici Chapel.

Research Algorithms

A research team headed by Marc Levoy, the associate professor of computer science and electrical engineering at Stanford who conceived of the project, is spending the 1998-99 academic year in Italy. The team—which consists of research associate Kari Pulli, five graduate and several undergraduate students—is applying state-of-the-art technology to digitize the famous statues. Once they have scanned a sculpture, the researchers will apply advanced algorithms developed at Stanford to convert the digital data into accurate, 3-D computer models. They will then create a matching overlay that contains additional data about surface color and characteristics required to reproduce the image accurately.

Levoy and his colleagues at Stanford's computer graphics laboratory have developed the algorithms over a period of several years. In 1996, they used the basic technique to create the world's first "3-D fax." To do this, they scanned a small statue, created a 3-D computer model of it and transmitted the model electronically to a stereolithography plant in Southern California that used the information to produce a detailed plastic replica of the original statue.

Uses For Virtual Sculptures

Once computer models of Michelangelo's statues have been created, they will have a variety of uses. The virtual sculptures can be viewed on a computer screen from any perspective, even those not visible to museum visitors viewing the actual pieces of art. For example, postcards sold at the Accademia Gallery in Florence show a close-up of the head of The David that cannot be seen by tourists because the statue is almost 20-ft tall. If the gallery includes a virtual model of the sculpture in its planned multimedia center, visitors could admire the sculpting of David's furrowed brow and piercing eyes for themselves, instead of relying on postcards.

Computer graphics can be used to virtually restore damaged areas of an artwork. It should be possible, for example, to reconstruct the beard of Michelangelo's sculpture Moses in San Pietro (Vincoli, Rome), as it appeared before it was worn down by the reverent touch of generations of visitors.

Through animation, art teachers can illustrate some of the tricks of perspective that Michelangelo used. In his Pieta, for example, he was the first to solve the problem of making a grown man fit neatly in a woman's lap. But he did so in part by giving Mary extremely long legs. Using animation to have Mary stand up would show this distortion plainly to art students.

Many ancient Greek statues were originally painted in bright colors. Computer models can be used to illuminate the sculptures with colored light so precisely that it looks as if the sculptures had been painted, even on close examination. With such a light system, visitors could turn on the lights to see how such a statue originally looked and turn them off to appreciate its current appearance. Such a lighting scheme also could be used to project outlines and other guides on damaged statues to aid in the restoration process.

A detailed computer model can be used to make accurate physical replicas of a sculpture at any scale. Currently, small replicas of important sculpture are not accurate because they generally are based on a contemporary artist's interpretation. Accurate replicas could be used for both research and commercial purposes. But Levoy emphasizes that the goals of his project are entirely scholarly.

Laser Scanners Uncover Sculpture Nuances

During the fall quarter, the Stanford researchers set up a temporary computer graphics laboratory adjacent to the Stanford Overseas Studies Center in Florence. There the team has been designing, building, and testing the three computer-controlled laser scanners and custom-built mechanical frameworks they will use in the scanning process.

Engineers at Stanford and Cyberware Inc. equipped this custom laser scanner with a 20-foot gantry to scan the sculpture of Michelangelo. (Photo: Marc Levoy)

The largest scanner is mounted on a 20-ft truss, can measure distances to within a quarter millimeter and was built to the researchers' specifications by Cyberware, Inc. (Monterey, CA). The second is a bread box-sized scanner mounted at the end of a precision robot arm that is designed to take measurements in hard-to-reach places. The third scanner is a test model that measures distances by the time it takes laser light to travel to an object and bounce back. It was built by Cyra Technologies (Oakland, CA), and can measure the distance of objects up to 300-ft away with an accuracy of 5 mm.

In their preparatory work, the researchers already have discovered a major error in the art history books. These volumes, and even the guidebooks sold at the Galleria dell'Accademia, uniformly agree that Michelangelo's David is 14.25-ft tall without its pedestal. But the computer scientists have determined that the famous statue, which sits on top of a 6-ft pedestal, is actually 17-ft tall.

"I expected our project to be historically significant," Levoy says, "I never expected it to start by correcting the history books." The statue's extra three feet of altitude created a major problem for the Stanford team. They used the official figures of its height to size their large scanner, so it was too short to reach the top of the actual sculpture. That forced researchers in Florence and at Cyberware's headquarters in Monterey to work through the holidays to extend the gantry by another three feet without compromising accuracy or safety, Levoy says. They were working against a tight deadline because Accademia officials made elaborate plans to hire extra guards and reroute tourist traffic during the scheduled scanning period.

The researchers intend to scan the sculpture The Unfinished Slaves first. They will do so with 1/4-mm precision. That will allow them to create a computer model that contains approximately 100 million triangles and provides sufficient detail to show individual chisel marks. The ability to capture chisel marks is particularly important in the case of this set of figures. Part of the sculptures' fascination lies in the fact that they are unfinished and so provide important insights into how the master sculptor worked.

Computer Science Challenges

Levoy expects the computer model of The David to run to tens of gigabytes, and the total for all of models the team intends to create will run into terabytes. The team has never dealt with 3-D models of this size before.

Scanning simultaneously for color and shape is also a questionable area. All three of their scanners will be equipped with color cameras for this purpose, but the researchers have never attempted to record both range and color at such a fine scale.

Finally, extracting the intrinsic surface reflectance of the statues will be a challenge. Getting the proper value for the surface reflectance is key to making the computer models look right under different lighting conditions. To do so, the researchers must process the images to remove the effects of shadows and highlights. They have done this in controlled lighting conditions in the laboratory. But doing it in the field, where the lighting is more variable, may prove more difficult.

"I think we know how to do all of these things, but putting them together will be a challenge," Levoy says.

Scanning Agenda

After completing their work with the sculpture in Florence, the group intends to move their operations to Rome, where Michelangelo's Pieta and Moses, along with Laocoon, one of the best-known works of Roman art, are on the agenda.

They also will scan the pieces of the Forma Urbis Romae, an ancient mosaic map of Rome. Levoy intends to use computer techniques to fit together pieces of the broken map. In addition, the group will take on other projects if time permits, such as scanning ancient musical instruments in the Medici Collection, including a Stradivarius violin.

Project Funding

The $1.5 million research project is funded by the Interval Research Corp. and the Allen Foundation for the Arts. Founded in 1992 by Microsoft co-founder Paul Allen and Silicon Valley veteran David Liddle, Interval Research is a high-technology laboratory that performs research and advanced development. The Allen Foundation is one of Paul Allen's charitable organizations.

"The Digital Michelangelo Project is an ambitious task that dovetails with Interval's research studies in new market opportunities at the intersection of technology and popular culture," Liddle says. "We believe that real-time interactive graphics have immense potential as a more effective tool for communications, education, and especially entertainment."

The project has required extensive cooperation from officials at the Italian museums and institutions that house the irreplaceable sculptures, including the Accademia Gallery, Medici Chapel, Superintendency of Fine Arts in Florence, Superintendency of Fine Arts in Rome and the Vatican Museum.

For more information, call 650-723-2558 or visit graphics.stanford.edu/projects/mich/.