Issue: Volume: 24 Issue: 9 (September 2001)

Preserving the Past

By Karen Moltenbrey

Imagine the historical and cultural toll if a flood suddenly decimated the Egyptian temples of King Ramses II, or a bomb blast turned the world's largest stone Buddha to mere pebbles. You may think that these scenarios are more apt to unfold on a movie screen than in real life. But consider this: Following an international campaign, the colossal Egyptian monuments at Abu Simbel were moved to higher ground so they wouldn't become submerged when the Aswan High Dam was constructed during the mid-1960s. And only a few months ago, towering Buddha statues hewn from a cliff in Afghanistan's Bamiyan province were reduced to rubble by the Islamic militia.
A pulsing green beam from a Cyra Technologies long-range laser scanner helps record hundreds of thousands of surface coordinates on a badly eroded gravestone at Kilmartin churchyard in Argyll, Scotland. The digital record will be used for conservation mon

Today, many other natural and man-made wonders are teetering on the edge of destruction. International groups such as the United Nations Educational, Scientific and Cultural Organization (UNESCO) are trying to safeguard hundreds of such cultural sites worldwide by designating them as areas needing protection. But efforts by conservationists, archaeologists, and others to keep these locations from becoming a fading memory are not always enough. Once a treasure is lost, so is the chance to study, analyze, or simply appreciate its impact on society. Through digital means, how ever, culturally significant sites can be preserved by committing them to computer memory, so these wonders of the past can be enjoyed by generations in the future.
This digital model of a walled temple complex at Phimai, Thailand, was created using Autodesk's AutoCAD and Discreet's 3D Studio Viz software. Originally planned as a promotional and educational tool, the virtual environment likely will be used to

The role of 3D computer graphics in preserving historical sites has grown significantly during the past decade. This expansion can be attributed to advances in scanning techniques, virtual reality, computing power, 3D modeling tools, presentation devices, and other related technologies, which have made it possible to accurately re-create buildings, antiquities, and even ecosystems for posterity. Virtual cultural heritage, as the ongoing preservation endeavors using these technologies are collectively referred to, also makes it possible to conserve and interpret an area, building, or object in ways that were previously inconceivable through photographs or other techniques. For instance, researchers can use a virtual replica of a monument to illustrate the destructive effects of pollution over a given period of time, or they can digitally restore a damaged building to its original state. More important, they can do this without altering or affecting the original specimen.
Thanks to advances in digital scanning, researchers can produce realistic 3D replicas of antiquities such as this clay tablet from Mesopotamia, believed to be a sales contract from 3000 BC. (Image courtesy Arius3D and the University of Chicago.)

"In the past, governments, tourists, and re searchers have physically altered our cultural legacy in an attempt to protect it," says Alonzo Addison, director of the Center for Design Visualization at the University of California, Berkeley, and a co founder of the Virtual Heritage Network (VHN), an international organization promoting the use of technology in cultural heritage. "More often than not, humanity could have benefited by leaving sites pristine for future generations. Virtual heritage enables us to experience, study, and better preserve with reduced physical impact."

The most immediate benefit of virtually re-creating a historical site is that it establishes a "living" record of a site that no longer exists. Yet, the technology is also solving one of the biggest issues concerning cultural heritage as sets-public destruction.

Several years ago, the British government barred public access to Stonehenge, one of England's most popular attractions, be cause acid from visitors' finger tips was destroying protective and aesthetic moss and flora growing on the stones. As an alternative, English Heritage, Britain's quasi-governmental preservation organization, hired Virtual Presence (Manchester , UK) to create an ac curate 3D record of the stones and their environment in their present state. "While not de signed to totally re place the real experience, the visualization is detailed enough to allow people to 'walk' among the stones and inspect the different textures in 3D," says Bob Stone, Virtual Presence's scientific director and a VNH co founder.
These interior and exterior images of a recreation building at Ancy Castle in Burgundy, France, were made for the Louvre Museum using laser scanning, photogrammetry, and 3D modeling. (Images courtesy SimTeam and AGP.)

The team created the representation from site data collected by English Heritage during an extensive survey of the area, which was input into Sense8's World Tool Kit real-time 3D development and viewing software. "Even the small surface features such as cracks, lichens, and fungi are visible," says Stone. The visualization also includes digital representations of related environmental features such as burial mounds. "The beauty of virtual heritage is that we can make people more aware and appreciative of the sites," says Stone. "For example, many people who visit Stonehenge don't know how it fits into the surrounding landscape."
This re-creation of a Sicilian dining hall from the late-sixth-century BC is part of virtual model that will be shown in a kiosk at the site's visitor center in Italy. (Image © 2001 Learning Sites Inc.)

Shortly after Virtual Presence created its Stonehenge model, Intel commissioned Superscape to produce a Web version of the project. While the reduced-polygonal model did not show the minute details in each stone, as did the high-fidelity model, it offered capabilities that the larger version did not, such as the ability to control a slider that presented the site at various stages through time. "Each model was de signed to display specific features based on the target audience and delivery method," ex plains Stone.
Using historical documents, researchers built this digital depiction of the famed Temple of Zeus, which no longer exists, as part of an effort to re-create ancient Olympia in Greece. (Image © 2001 Powerhouse Museum)

Early data-intensive virtual heritage projects, created by universities or commissioned by large companies, were performed on costly supercomputers or produced as prerendered animations on video. And yet, the accuracy was limited by the hardware and software that were available. "Although a growing number of low-resolution, three-dimensional, and even immersive virtual tours, photo al bums, and multimedia pieces have been constructed, few of the early forays [in the mid-1990s] satisfied the preservationist's need for documentation, the historian's need for interpretation, or the public's need for visual realism," says Addison. These early models were mostly intended as reconstructions and database studies of sites that no longer exist, and were rarely used as proactive tools for conservation or the future preservation of a site, as they are now, notes Scot Thrane Refsland, a VHN cofounder and a researcher at UC Berkeley's Center for Design Visualization.
Physical reconstruction and archaeological work at this temple site in Myanmar (formerly Burma) have done more harm than good, as destructive enamel paints have been applied over delicate thousand-year-old murals. Virtual technologies can help sites like

As the digital tools have matured over the years, so too have the applications at both ends of the reality spectrum. At the high end are authentic augmented-reality pieces that run on complex machinery. These visualizations, which may run in CAVEs or Reality Centers, are usually produced at universities and funded by national budgets for conservation, preservation, and interpretation purposes. At the mid-range and low end are flythrough applications targeted at global audiences for educational purposes.
Virtual models can reveal information that might otherwise go unnoticed. For example, visitors can't get close enough to Stonehenge to see this graffito (highlighted in lower image) by the noted English architect Christopher Wren. (Images courtesy Bo

The recent high-fidelity projects are living up to their promise of re-creating reality, thanks to the tools and techniques now emerging from academia, government, and industry labs that enable accurate data collection, representation, and dissemination. Ac cording to Addison, a major breakthrough in the data collection process has been the introduction of 3D digitizing systems such as laser scanners, photogrammetry, and image-based modeling software, which have made it possible to rapidly gather extensive and highly accurate data sets for constructing virtual worlds. "Virtual heritage can be an invaluable tool, but if not applied wisely, it has the potential to do as much harm as good," says Addison. "Dozens of virtual Pompeiis now exist, yet few are historically accurate or reliable enough to be truly useful, while others are even misleading. Therefore, historical accuracy is perhaps more important than ever in the new digital landscape."
Using a laser scanner, spectral camera, digital camera, and charts for color calibration, modelers at UC Berkeley and the Universities of Ferrara and Rome collected millions of survey-grade 3D coordinates and color textures to reproduce a bay of Rome'

One of the more compelling projects using close-range laser scanning, panoramic photography, and 3D modeling is Virtual Olympia, created by Sarah Kenderdine, curator/creative producer of special projects at the Power house Museum in Sydney, Australia, to complement an exhibit at the 2000 Olympic games. Kenderdine, along with John Ristevski and Cliff Ogleby from the University of Melbourne and photographer Peter Murphy, created a historically accurate stereoscopic reconstruction of ancient Olympia and the Temple of Zeus using architectural, archaeological, cultural, aerial, and geological information.

Recently, Virtual Presence's subsidiary SimTeam (Paris), along with AGP (Joinville le Pont, France), used photo grammetry, laser scanning, 3D modeling, and proprietary compression software to create a real-time virtual restoration of the thirteenth-century Amiens Cathedral in France, depicting the building and its artwork in their original state. Once the team created the complex models, it then digitally repaired the damaged sculptures and statues using SensAble Technologies' Phantom force-feedback technology and FreeForm "virtual clay" product. The artists also used a proprietary texture-mapping tool to restore the faded art to its original brilliant colors. Using SimTeam's proprietary Praxitele compression software, the group overcame another huge VR obstacle by creating precise models that can be manipulated in real time without lowering the quality of the image.
Researchers from UC Berkeley recently completed a virtual recording of the Inca ruins at Tembo Colorado on the Peruvian coast in what may be the largest and most extensive 3D laser survey of a heritage site. At the top is a picture of the actual site. The

At Angkor Wat in Cambodia, archaeologists, conservators, and maintenance crews are employing photographic-based techniques to analyze and slow the decay at the twelfth-century temple complex, the largest religious stone monument in the world. Today, monks live at the former sanctuary, and tens of thousands of pilgrims visit yearly. Their physical interaction with the enormous carved sandstone reliefs, along with the climate's tropical moisture, are causing the structures to decay rapidly. A team from the University of Cologne in Germany, led by Hans Leisen, is tracking the degradation on a digital model created from high-resolution photos and individually documented layers representing each form of decay (cracking, flaking, etc.), which were produced in Autodesk's AutoCAD software. "Using an architectural tool gives us the capacity to measure, calculate surface areas, and perform other analytical functions to try and slow the decay," says Simon Warrak, chief conservator. "As a result of our efforts, we're extending the life of the site, albeit perhaps only a few years for the areas in the worst condition."
A team of curators, archaeologists, surveyors, and photographers captured high-resolution data sets that were used to create this virtual reconstruction of Olympia in the year 200 BC. (Image copyright 2001 Powerhouse Museum.)

In Xi'an, China, researchers are fighting another natural battle, this one against white ants that are gnawing their way through ancient landmarks and threatening the city's famed terra-cotta warriors, an army of life-size clay soldiers, horses, and chariots found inside the tomb of China's first emperor, Qin Shihuangdi. Archaeologists have spent 20 years unearthing 3000 of the estimated 8000 statues, many of which were broken long ago. To speed the recovery process and to prevent further damage to these delicate objects during excavation, a team led by Jiang Ju Zheng, former associate professor at Kyushu Institute of Technology in Japan, devised a virtual recovery method using a portable laser range finder and proprietary imaging technology. The technique produces a depth and color map of an object, so archaeologists can precisely document and model unearthed objects. The group also created customized software that enables researchers to piece together 3D fragments of the broken statues without harming the originals.
Through complex modeling techniques, artists restored digital versions of the intricate statues from the Amiens Cathedral to their original brilliance from the Middle Ages. (Images courtesy SimTeam and AGP.)

While aesthetically captivating, these authentic virtual worlds have until recently been largely static and lifeless. However, with today's global networks and fast computers, re searchers are now able to bring these worlds to life. In their re-creation of the golden temple of Kinka Kuji in Japan, Refsland and colleagues at Gifu University in Japan incorporated artificial intelligence features into 3D models of fireflies, which were inserted into the virtual environment for effect. The in sects were connected in real time to the Nasdaq stock exchange, whose trade movement sparked the random motion of the fireflies within the scene.
Most archaeological finds incur damage during excavation. But a new virtual recovery method enables archaeologists to create digital models of unearthed relics, such as these from Xi'an, China, using a sophisticated laser-scanning technique. (Image co

Refsland has extended this research into a brand-new project called Virtual Snowshoe Mountain, which he created using customized GIS satellite, terrain, and photography data that's linked to real-time weather service information. The result is an accurate, living simulation of the actual area. "What you experience in virtual reality is really happening on the mountain," he says. "If it's snowing, then it's snowing in the virtual environment." In fact, the entire model is mapped to the real environment through sun positions, clouds, seasons, precipitation, and the like. Refsland has also mapped artificial life creatures to the real-time information, so their behavior is likewise related to the real environment. For instance, if it's snowing, then the virtual birds in the 3D environment will not be present to search for food. "This new style of living virtual environment, or enhanced environment, provides users with a more immersive feeling of the site, as if they were really there," Refsland adds.
Stone reliefs at Angkor Wat in Cambodia are rapidly deteriorating, as can be seen in a comparison of photographs taken of the same carvings in 1965 (left) and 1995 (center). Using digital modeling, conservators are mapping and analyzing the decay (right).

According to Stone, using virtual models to educate the public and teach them how to respect existing facilities is paramount to cultural preservation. "The content must teach visitors how to respect the site to ensure its survival for generations to come," says Stone. This can only be ac com plished, though, if the models can be viewed by the general public. Until a few years ago, offering widespread accessibility of virtual heritage models was unthinkable. But now, with powerful, low-cost multimedia computers and graphics cards, in creased Internet bandwidth, and widespread availability of VR modeling and run-time software such as DirectX and OpenGL, it's possible to deliver a virtual experience that offers an impression of reality to just about anyone, anywhere. However, bringing virtual heritage applications to the desk top, where they can be easily shared, is difficult, given the large amount of data that's required to construct an authentic model.
Scientists added life to a digital model of a Japanese temple by connecting the activity of 3D fireflies to the movement of stock trades. (Images courtesy Scot Thrane Refsland.)

"Some groups are creating extremely detailed visualizations that can only run on a supercomputer, so they are only viewed by a select group of re searchers and scientists. While that level of accuracy is essential for recording an artifact or site for posterity or historical projection, it is unnecessary for an educational perspective," Stone maintains. "All you need for this general audience is a visually appealing representation that's rich in content." This can be done, for instance, by creating a low-resolution model and augmenting it with hot spots that link to other forms of media, such as VRML models, MPEG files, or AVI clips.
Researchers have linked a synthetic model of Snowshoe Mountain in West Virginia to actual weather service data, so when it rains at the actual location, it rains in the virtual environment. The visualization, created in Maya, uses Epic's new Unreal Warfar

Virtual Stonehenge, created in the mid-1990s, was the first virtual heritage project to break the supercomputing boundary by running on a Pentium Pro platform. This trend continues today with sophisticated 3D worlds that run on off-the-shelf Pentium IIIs with accelerated graphics boards such as Nvidia's GeForce. One company that's using the desktop platform to push the reality envelope is Learning Sites (Williamstown, MA), a company that creates digital heritage site models for museums, schools, and archaeologists. Unlike most other such projects, which are produced by 3D artists, Learning Sites' visualizations are created by a team of 3D modelers, archaeologists, architects, and art historians.

"Our applications are used as research tools by students, scholars, and museum personnel, so they have to be precise," says Don ald Sanders, president of Learning Sites and himself an architect and archaeologist. "We can accomplish this by asking the site archaeologists key questions about the architecture." Using this data, along with proprietary navigational tools, the company has re-created numerous sites throughout the Mediterranean region that run on the desktop or in a CAVE, depending on the client's needs. Sanders hopes to make these and similar historical visualizations more accessible to the public when he launches the Institute for the Visualization of History, a venue he plans to build somewhere in New England that will incorporate leading-edge computer technologies, including holograms and CAVEs, for immersive viewing experiences.
A new trend in virtual heritage is re-creating industrial sites from the not-so-distant past, such as this ongoing restoration of the Lion Salt Works in Northwich, England. (Images courtesy of Bob Stone)

According to Sanders, two major technology evolutions that have made compelling desktop applications a reality are computer game engines and VRML for easy 3D navigation. "Game companies have spent millions of dollars developing real-time 3D engines that specifically deal with presenting textured and shaded 3D worlds on standard PCs," says Victor DeLeon, creative director of Digitalo Studios (Coral Springs, FL). While at the University of Gifu during the late 1990s, DeLeon and his team were the first to develop high-resolution, real-time virtual heritage projects-the Florida Everglades and Notre-Dame-driven by 3D game-engine technology.
This re-creation of the Northwest Palace of Ashur-nasir-pal in Iraq runs on various platforms, from PCs to CAVE installations. It unites, for the first time in thousands of years, relief sculptures that are now scattered in museums and collections around

While the introduction of gaming technology has been a big boost for desktop projects, these applications still can not compete with the realism and historical accuracy of their super computer-based brethren. "Access to virtual heritage on the desktop is slowly moving in the right direction, but there are still many technological obstacles, such as the lack of high-speed bandwidth in most locations for downloading Web-based applications and a real data standard for Internet content," Stone says.
This virtual model of Notre-Dame, powered by Epic's Unreal game engine, offers viewers a virtual walkthrough of the cathedral and virtual guided tours by digital friars. (Image courtesy Digitalo Studios, Inc.)

The past decade has witnessed a rebirth of history through virtual reconstruction. But the progression toward digitally preserving cultural sites has been slow; fewer than a dozen of the nearly 700 designated UNESCO World Heritage sites have been virtually re constructed as authentic re-creations. Unfortunately, time is often a historical site's worst enemy. For areas that need immediate attention, Sanders hopes to assemble a digital swat team that can respond to a location for emergency data collection.

"We're hoping to use the Afghanistan situation [involving the destruction of the Buddha statues] as a springboard for alerting people to such crises and showing them how digital preservation can be used as a means to record the condition of a precious site before it becomes extinct," Sanders says. While it's too late for such action in the case of the Buddha statues, Sanders believes there is still a chance of digitally preserving the site, and has contacted scholars around the world who have photographed and studied the region prior to the destruction, so a digital model can be made.

Besides time, other limiting factors to virtual heritage are money and available information, according to Richard Levy, associate professor of planning and urban design at the University of Calgary. "These projects are extremely time-consuming and expensive," he adds. Until now, most of the projects have been funded through government grants and academia, especially in locales sensitive to their deteriorating cultural assets such as in Europe, Asia, and Australia. "Although all sites need help, many well-known and well-protected landmarks receive a disproportionate share of scarce technological expertise," notes Addison. "Since many sites are in physically or technologically re mote locales, we must strive to avoid the perception of cultural or digital imperialism."
Digital measurement and data-collection tools enable increased precision for virtual models, such as this re-creation (top) of the present-day baths at Caracalla, Rome (bottom). (Images courtesy Marco Gaiani, Alonzo Addison, Marcello Balzani, and Federico

According to Sanders, site access, especially in countries experiencing political unrest, is also a huge stumbling block. Just as problematic is obtaining access to the antiquities found in museums and cultural centers, which are usually unwilling to share their treasures so openly for fear of losing visitors.

Issues such as these, which are slowing the progress of virtually re-creating historical sites, will be discussed at a virtual heritage colloquium, held during the International Society of Virtual Systems and Multi Media's international conference at UC Berkeley next month. The session will be chaired by Addison and Minia Yang, deputy director for World Heritage at UNESCO.

Re-creating historical sites using virtual technology is still in its infancy, but the necessary technologies and their subsequent applications are springing up, breathing new life into the ancient past. And this is happening just in time, too, as the obliteration of many of these landmarks could be just a disaster away.

Karen Moltenbrey is a senior associate editor for Computer Graphics World.

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