The Digital Michelangelo
Project:
Creating virtual
versions of world-famous sculptures
BY DAVID F. SALISBURY
Through the magic of
advanced computer graphics, art lovers soon may be able
to examine highly realistic, three-dimensional images of
the statues of Michelangelo on display screens at their
local art museum, or even on their personal computers.
The technology will 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 maybe even animate the
classic figures.
The Digital Michelangelo
Project, an ambitious effort to create the first
authoritative, 3-D computer archive of the 15th-century
Italian artist's most famous sculptures, is laying the
groundwork for these capabilities. The project not only
holds the promise of making virtual copies of
Michelangelo's statues available for appreciation and
study around the world, but it also may set a new
standard for the computer representation of
three-dimensional physical objects.
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 these priceless art treasures. In mid-January, 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 they are scheduled to move to
the Medici Chapel.
This
custom-built device, designed expressly for the
digitization of large statues, arrived Thanksgiving Day
at Levoy’s lab in Italy.
Courtesy
MarK Levoy
Marc Levoy,
the associate professor of computer science and
electrical engineering at Stanford who conceived of the
project, and a research team 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 an accurate, three-dimensional computer model.
They will then create a matching overlay that contains
additional data about surface color and characteristics
required to reproduce its image accurately.
Levoy and his colleagues
at Stanford's Computer Graphics Laboratory have been
developing these algorithms for several years. In 1996,
they used the basic technique to create the world's first
"3-D fax." 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.
The Digital Michelangelo
Project will produce some of the largest 3-D computer
models ever made. It will also combine color and shape
information at a level of detail never before attempted.
3-D computer models
have a variety of uses
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. Postcards sold at the
Accademia Gallery in Florence show a close-up of
the head of "The David," but no tourist
can see this view because it's 20 feet in the
air. 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 as closely as
they like.
- Computer graphics can
be used to "virtually" restore damaged
areas of an artwork. It should be possible, for
example, to reconstruct what the beard of
Michelangelo's sculpture "Moses" in San
Pietro in Vincoli, Rome, looked like before it
was worn down by the reverent touch of
generations of Jewish 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.
- 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.
The $1.5 million research
project is funded by the Interval Research Corporation
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 has immense potential as a
more effective tool for communications, education, and
especially entertainment."
Computer graphics
laboratory set up in Florence
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.
The largest scanner is
mounted on a 20-foot truss, can measure distances to
within a quarter millimeter, and was built to the
researchers' specifications by Cyberware Inc. of
Monterey, Calif. 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 of
Oakland, Calif., and can measure the distance of objects
up to 300 feet away with an accuracy of 5 millimeters.
"The David"
is three feet taller than art textbooks say
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 "The David" is 434 centimeters (14'
3") tall without its pedestal. But the computer
scientists have determined that the famous statue, which
sits on top of a six-foot pedestal, is actually 517
centimeters (17') 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 a quarter-millimeter
precision. That will allow them to create a computer
model that contains about 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 issues
"From a computer
science perspective, there are several issues that we
must deal with," Levoy says.
First, he 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. They have
never dealt with 3-D models of this size before.
Scanning simultaneously
for color and shape is also a question mark. All three of
their scanners will be equipped with a color camera 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 the 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.
After completing their
work with the sculptures 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.
The project has required
extensive cooperation from officials at the Italian
museums and institutions that house the irreplaceable
sculpture, including the Accademia Gallery, Medici
Chapel, Superintendency of Fine Arts in Florence,
Superintendency of Fine Arts in Rome, and the Vatican
Museum. SR
Digital
Michelangelo Project team members paused while packing up
their equipment for a trip to Italy in September.
Clockwise from bottom right are Sean Anderson, Lucas
Pereira, associate Professor Marc Levoy, David Koller,
John Gerth, Kari Pulli and Szymon Rusinkiewicz.
Courtesy
of MarK Levoy
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