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Direct Dimensions Inc.

Metrology

Modern 3-D Technology Virtually Restores Ancient Roman Sculpture

Scholars create historically accurate statue of Emperor Caligula

Published: Tuesday, February 7, 2012 - 14:44

The city of Rome is one of the most popular destinations in the world owing to its culture, architecture, and especially the art that remains from its ancient citizens. Every year millions of people visit the travertine stone remains of the Coliseum, the Roman Forum, and other sites, wondering what life must have been like at the height of the empire.

Bernard Frischer, Ph.D., of the University of Virginia and the Virtual World Heritage Laboratory employs 3-D technologies to answer that question. In 2007 he initiated the “Rome Reborn” project to build a 3-D digital version of the original Rome, circa 320 A.D. Today he is directing the Digital Sculpture Project to exploit 3-D scanning and modeling technologies for the “capture, representation, and interpretation” of ancient sculpture.

During the past year, Direct Dimensions worked with Frischer’s team to digitally re-create a famous life-size marble sculpture of the Emperor Caligula from first-century Rome. This project resulted in a unique combination of 3-D technologies and academic research.

The Caligula sculpture is owned by the Virginia Museum of Fine Arts (VMFA) and, as one of only two complete existing sculptures of the emperor, is also considered one of the most important Roman “portraits” in the United States. Although the sculpture is in generally good condition, it suffered damage through the years—such as losing its nose and hands, missing chunks of the toga, and a poor repair job some years ago that misplaced Caligula’s head.

A team of experts from around the world was assembled to research how the Caligula sculpture might have looked when it was first created. But how would the team collaborate with scientific accuracy on such a large, complex sculpture located in Virginia?

The answer: utilizing advanced laser scanning technology to accurately digitize the physical sculpture, thus allowing the team to collaborate virtually in 3-D.

In September 2010, our engineers traveled to the Virginia Museum of Fine Arts, where they spent a full day capturing the Caligula sculpture with a laser line scanner mounted on a Faro Arm portable articulating digitizer. They scanned the entire complex piece with an accuracy of about 0.1 mm and resolution of nearly a 0.25 mm. The resulting 3-D point cloud file was more than 1.5 GB and contained nearly 137 million points.

https://lh3.googleusercontent.com/h1yfCTysPm-_MOkx9l7bcDyhDXWAK_cu22TD6m7-hi2Acbay_CRo9Ie22H5E8yzqDl7lq8NCf7RId8JrsJBjWuC61PR--lDHwnRkyb4-O33CrtPZEuQ
On September 2010, Direct Dimensions traveled to the Virginia Museum of Fine Arts in Richmond, Virginia to 3-D laser scan the Caligula statue.The scanning took a full long day using the Faro PlatinumArm, the Faro LaserScanner, and PolyWorks software.

Back at the DDI facility in Baltimore, the raw laser data were processed into a super high-resolution polygonal model using Innovmetric’s PolyWorks Modeler software. For technical reference, the final model was nearly 400 MB in size and contained more than 9 million polygons. Because this model was watertight, the team also calculated the exact surface area of marble, just less than 5 million square millimeters.

However, this “exact” digital replica model of the existing condition piece was only the first step in their work. The goal for the project was not simply to re-create the Caligula sculpture as it looks today, but how it might have looked when it was originally created almost 2,000 years ago. Given its current condition, this meant digitally restoring the missing hands and nose, replacing the missing pieces of the toga, and even “repainting” the sculpture. (Note: Although all that we see today is the marble, the ancient Romans actually painted their sculptures in brilliant colors, which have worn off over the passing years.)

To perform these tasks, the Direct Dimensions’ digital modelers worked in close collaboration with the international academic research team to digitally sculpt and repaint the missing elements of the sculpture. Using ZBrush software, for example, the modelers created the shapes for the missing parts, such as the hands. The academic experts then indicated how the modelers needed to adjust the hand positions to be representative of the time period.

Using those examples, exchanged digitally across the Internet, the DDI modelers were able to iteratively sculpt new versions of the missing components. The research team was then able to suggest edits based on their hypotheses, leading to the creation of multiple digital models.

https://lh6.googleusercontent.com/hcd8lBQUAVyEoqCAezRJ6eQ9LiuBbZLZaDTkxPHvkUNbp6r2ACzM2946qn79cufmEEKiS3nKRanMpfhe0oybTCSY4dqxHg3Idx0JrxL3Hes7xLm10Z0
From left: Original Caligula scan, painted scan, painted Copenhagen Caligula used as reference.

This process was repeated for many of the missing elements and also to help with the positioning of the separated head. After exchanging and studying many iterations, the researchers ultimately selected the final configurations and the project continued to colorization.


Original Caligula and virtually restored Caligula

When it came time to repaint the digital model, it turned out that very faint traces of the original polychromy (color) still existed, allowing the research team to provide a likely color scheme to Direct Dimensions. Again using ZBrush, the DDI modelers created a layering of colors on the digital model, which they could turn on or off to display likely depth of color to the academic researchers. For instance, trace findings indicated that part or all of the toga was once painted purple, and the model was able to display slightly different purple colors as well as options for an entirely purple toga and also a simple purple sash.

The final digital model was unveiled to the VMFA on Dec. 4, 2011, during a special symposium entitled “Caligula 3D: Man, Myth, Emperor.”

A slide show of the project can be viewed here.

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Direct Dimensions Inc.

Direct Dimensions Inc. (DDI) provides products and service solutions to complex modeling and manufacturing problems, specializing in the on-site application of digitizers, laser scanners, and the conversion of complex 3D data into 3D computer models. DDI enables innovators to capture, model, and modify complex physical shapes, such as organic human forms, that would otherwise be impossible to design even with today’s advanced CAD systems. DDI’s engineers provide data measurement, inspection, and reverse engineering solutions in product evaluation, development, and manufacturing; in cultural preservation; medical prosthetics; and color 3D imaging for consumer applications.