Reconstructing the Center of Civic Life
undreds of Web sites are devoted to Pompeii, the Italian city buried beneath volcanic ash and dust from the 79 A.D. eruption of Mt. Vesuvius: evidence of the hold this ancient city has on modern imaginations. To reconstruct a glimpse of life at the height of the Roman Empire, a team of scientists at the University of Virginia is creating 3-D computer models of ancient structures found in the forum, or city center, at Pompeii. By applying computer technologies, the Pompeii Forum Project is helping urban historians, engineers, archaeologists, and architects study how the citizens of Pompeii rebuilt the forum after an earthquake in 62 A.D.
Roman writings document the occurrence of the lesser-known Pompeii earthquake, but provide little detail concerning its effects, which are of great interest to researchers in urban history and design. They see in the remains of Pompeii a basis for creating an account of the life of the city between the earthquake and subsequent volcanic eruption.
The Pompeii Forum Project at University of Virginia's Institute for Advanced Technology in the Humanities (IATH)--an NPACI Education, Outreach, and Training partner--is a collaborative research venture that is archaeologically based, heavily dependent upon advanced technology, and so conceived as to address broad issues in urban history and urban design. John J. Dobbins, an IATH Fellow in 1993-94, is the project's director.
"The Pompeii Forum Project is an excellent example of how advanced technology can be brought to bear on some of the most interesting research questions within the humanities," said John Unsworth, director of IATH and an associate professor of English at Virginia. "Visualization opens new doors for researchers to represent everything from literary works to archaeological reconstruction, all of which contribute to the body of knowledge and understanding in these disciplines."
The institute, founded in 1992, was the vision of William Wulf--the AT&T Professor of Engineering and Applied Science at Virginia and president of the National Academy of Engineering--made real through support from IBM. Fellowships in Residence at the institute are granted to a select number of Virginia faculty each year, and to teams of researchers at other universities who participate over the Internet as Network Fellows.
"Studies in the humanities are traditionally strong at the University of Virginia," Unsworth said. "Bill expected that some of the most interesting computing problems of the future would come from this area."
The IATH goal is to explore and expand the potential of information technology as a tool for humanities research. To that end, Fellows receive consulting, technical support, applications programming, and networked publishing facilities. IATH also cultivates partnerships and participates in humanities computing initiatives with libraries, publishers, information technology companies, scholarly organizations, and others interested in the intersection of computers and cultural heritage.
The Walls of Pompeii
To create a realistic 3-D model of Pompeii's Macellum, the members of the Pompeii Forum Project build small segments of walls in VRML (left) and then mapping photographs of the actual walls onto the model (below). The segments are then "stitched" together to form a larger model.
The former city of Pompeii is centered on the forum--a space of temples and administrative buildings--surrounded by 117 blocks of ruins, all contained within crumbling city walls. The form and face of the forum changed with each political incarnation of the city. According to Carroll William Westfall, an urban historian who has participated on the Pompeii Forum Project, under Roman rule the forum achieved a new prestige as the Romans used civic activity and accompanying urban architecture to show that religious and civic life gave order and vitality to the private and commercial affairs of the city. The remains of the forum therefore provide a visual history from which to read the state of civic affairs when Mt. Vesuvius erupted.
The archaeological record of Pompeii, however, presents inconsistencies that have long intrigued scholars. Specifically, the buildings of the forum appear deteriorated or partially repaired when compared to surrounding buildings. The earthquake of 62 A.D. accounts for the damage to the city as a whole, but urban historians wonder why the central space of Roman life was allowed to linger in a state of seeming disrepair.
Evidence gathered to date by the Pompeii Forum Project challenges commonly held and widely published notions about the evolution of the forum, especially during the final years of the city's life. The project aims to provide the first systematic documentation of the architecture and decoration of the forum and to interpret this evidence as it pertains to the city's urban history. According to Westfall, this reading of Pompeii is applicable to subsequent and contemporary problems in urban design, or how urban architecture supports city life and the well-being of its citizens.
Structural engineering principles might offer insight into such archaeological questions about the reconstruction following the earthquake. Kirk Martini, an assistant professor of Architecture and Civil Engineering at Virginia and an IATH Fellow, has been applying terrestrial photogrammetry to create a 3-D model of the Macellum--a large market building on the Pompeii Forum.
Photogrammetry uses photographs to derive 3-D geometry, which can be modeled with methods such as the Virtual Reality Modeling Language (VRML). The 3-D models are generated by the EOS Systems Photomodeler program. The surface textures from the photographs are mapped onto the model so that it shows not only geometry, but also surface material and texture, effectively creating a 3-D photograph that can be viewed from any angle.
Martini and a multidisciplinary team of researchers and students at Virginia are currently creating a partial model of the Macellum using approximately 100 photographs: a challenge to the Photomodeler software that has led the team to develop a process called "stitching." Worthy Martin, professor of computer science, students Randy Hudson and Tony James, architecture student Rodrigo Abela, Martini, and IATH graphics specialist Chris Jessee are collaborating on the four-step process, which allows the modelers to create a large VRML model of the building by joining smaller models created with Photomodeler.
The motivation for this approach lies in the fact that photogrammetry is more effective when applied to a group of photographs that include many common points in a scene; the large building is broken into parts that can be covered by roughly six to 10 photographs, with some overlap common to the parts. The geometry of the parts can be calculated effectively, and then the parts can be stitched together at the overlaps.
The four steps of the stitching process are to identify corresponding regions of triangles between two models, calculate a transformation that roughly aligns one model with the other, calculate from that starting position a more refined transformation that minimizes the error in the alignment, and then merge the matched vertices to produce one complete model. In the future, Martini hopes to work closely with the NPACI Interactive Environments thrust area to expand these types of modeling activities.
The researchers can also enhance the models to recreate the building before the earthquake and use that data about prior form and seismic effect to extrapolate the effects of the earthquake on other structures. They can then compare the degree and chronology of reconstruction in private buildings to the reconstruction of the forum.
"Architects, archaeologists, and computer scientists build and analyze computer models of structures, and construct a chronology of events that matches the evidence in the masonry," Martini said. "The results drive urban historians' theories about the life of the civic center of Pompeii. Many disciplines contribute to the work of the project, and in the end we all benefit."--AF