Virtual restoration.(lighting)

One of the most stunning animations premiering in the Electronic Theater at SIGGRAPH 2004 was a computer graphics tour de force, titled "The Parthenon," which, in two and a half minutes, visually restores to its original glory the ancient Greek monument that has stood at the head of the Athenian Acropolis for two and a half millennia.

The film--created by a team led by Paul Debevec, executive producer of graphics research at the Institute of Creative Technologies (ITC) in Los Angeles and research assistant professor at USC--applied new techniques to reassemble and renew the Parthenon, considered to be one of the world's most architecturally refined structures.

Constructed in 432 B.C. as the temple to the goddess Athena, the Parthenon has been damaged by wars and the elements over the centuries. Adding insult to injury, most of the classical statues and sculptures decorating the monument were removed in the early 1800s and placed in the British Museum, where they remain on display today.

To create CG models of the sculptures, Debevec's group developed a 3D scanning system consisting of a standard 1024x768 video projector and a 1KXlK video camera. With the device, researchers captured 2200 scans, accurate to approximately 1mm, which they assembled into precise models. Next, they employed a 3D laser scanner, taking some 120 panoramic scans of the Parthenon and collecting more than six billion point measurements, which were assembled into a 90-million polygon model.

Once the CG models were completed, the team devised a novel method of generating accurate color texture maps that overcomes the shortcomings of traditional techniques. Rather than simply using digital photographs--which record surface colors only as they appear under lighting conditions that can vary widely according to cloud cover, time of day, shadows, and so forth--the researchers ...