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THE PAST REBORN.DIGITAL RESTITuTION OF THE ARCHAEOLOGICAL

SITE OF POLIZZELLO

Alessandro Fiamingo*, Enrico Greco*, Emanuele Sangregorio*, Riccardo Giovanni Urso*

* University of Catania, Italy (fiamingo.alessandro@gmail.com, egreco@dmi.unict.it,

sangregorioemanuele@gmail.com, riccardourso@live.it) AbstractIn the last decade, the use of 3D reconstructions of antiquities has become a well established trend that is now widely applied to increase the value of cultural heritage. Only recently 3D computer graphics have been interpreted also as a cognitive tool for the archaeological research, especially with regards to the great monuments of classical civilization. The decision to produce virtual models of pre-protohistoric monuments, often characterized by bad preservation of the remains and lack of other classes of documentary sources, can be considered as a real challenge for archaeologists and experts.This work, fitting the interests of Catania University’s Archeomatica Project (www.archeomatica.unict.it), aims to create a multi-phase virtual model, integrating the natural landscape and hu-man constructions, of the Polizzello Mountain site (Mussomeli, CL), that flourished between the 10th and the 4th century BC. In particular, in this paper, the 3D models of two large holy enclosures are presented. They were interpreted as the focus of the activities of the acropolis of the site between the 8th and the 6th century BC. The elaboration has taken into account all the classes of data collected during the excavations, which have been recently completed, in order to give the philologically correct replica of what the buildings were at the time of their use. The work tool chosen is Blender, an open source, multiplatform software that is extremely powerful and versatile in 3D modelling, rendering and animation.

Keywords: 3D modeling, Pre-historical sites, Open Source, Digital archaeology

Reconstructing the human presence in historical settings has recently become the aim of several scientific co-operation programs between archaeological and computer science personnel. In particular, computer graphics help researchers to reconstruct original locations starting from a simple plan. Digital Archaeology therefore improves the quality of the data available in archaeology. 3D modeling allows some of the most important buildings of the classical or near-eastern cultures to be reconstructed in order to diffuse knowledge about this world. As stated by article 12 of the 1964 Venice Charter of international council on monuments and sites, “Where traditional techniques prove inadequate, the consolidation of a monument can be achieved by the use of any modern technique for conservation and construction, the efficacy of which has been shown by scientific data and proved by

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experience”. Despite a certain level of success, the reconstructions made to date have not been very detailed, and are usually inaccurate. In the last few years, several research projects have begun in order to provide optimal reconstructions that include also all the data sets from the prehistoric excavations. The most important projects concerning prehistoric research in the Mediterranean area have been carried out by the University of Bristol in Malta (Xaghra Circle) and by the University of Southampton in Sicily (Troina Project). The basic idea is that archaeological 3D modeling adds the possibility of creating virtual reconstructions to the usual graphic and photographic documentation. These reconstructions help to show how the place originally looked and in some cases this is the easiest way to reach it. In the case study selected for this paper, the Acropolis of the Polizzello Mountain, two circular precincts, A and B, were chosen for 3D modeling reconstruction with Blender (www.blender.org).

The excavation of building A, on the northern side of the hill, was of primary importance to clarify the most ancient traces of occupation in this area. With 8 meters in diameter, it shows, in the perimeter wall, a particular building technique with a double rows of regular blocks filled with chaotic stones and an entrance on the southern side. The pavement is composed by a thick layer of pebbles, gravel and beaten earth. On the west side is placed a ring-shaped bench. In the centre of the pavement lies a set of flat stones that could be interpreted as a base for a wooden statue of the deity. Not distant a huge parallelepiped block stone is placed, probably used as an altar. Several depositions, dated back to the 7th BC, have been found on the pavement. They are characterized by the constant presence of food remaining, ashes and animal bones. Among these are worth of mention some oinochoai with an indigenous style painting, an iron sickle, two iron dagger blades intentionally broken and several ornamental elements like bone, amber, bronze rings beads. Furthermore, underneath the building A an older structure dated to the mid 9th century BC, called the North Building, was identified. From an architectural point of view it seems to be composed of a large main room with trapezoidal shape which, although mutilated to its southern end, has an appreciable length of about 15 m and a width of 6.70 m. The presence of a second stiffer area, maybe a store room, of about 3.50 m to the East is quite likely. At least two openings are recognizable: the first one on the north side and the second on the east side. Along the east wall haven’t been detected signs of internal divisions and the pavement was uniform without re-adaptation. Inside the trapezoidal room has been found a large amount of crockery that suggests the practice of community activities like meals and libations.

Building B was surely one of the most important structures of the proto-archaic and archaic sanctuary. It was an open precinct 10 meters in diameter with access from the south side and a small semicircular room on the east and perimeter walls are built with the same techniques of the building A. Inside there was a central hearth and along the walls were stone furniture elements such as altars and benches. A large paved area was discovered outside by the access point. 255 objects were found on the floor of Building B, including vessels, weapons, clay models and exotic goods in amber, glass and ivory, divided into 17 groups of votive deposits,

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and found in excellent condition. Several of the most significant objects show a strong link with ancient Minoan religion and an important link between Polizzello Mountain and Crete was also shown by the discovery of a rare bronze helmet of Cretan type and of a couple of female ivory figurines of sub-daedalic type.

The two buildings are slightly intersecting each other so that they share a portion of the outer precinct, indicating a later chronology for building B in comparison to Building A (Fig. 1).

About the phases of the digital reconstruction, for the building A the first step was the recreation in CAD environment the perimeter, the imported in Blender. The modeling was done in wireframe mode in order to reproduce better the surface of each stone and respect the proportions and the positions identified during the excavations. Then every polygon representing each single building unit, has been revised and extruded generating a three-dimensional model imitating the original building texture of the perimeter wall. The only two layers of basement well preserved were enriched with the adjunction of a third one to enhance the readability the specific herringbone building technique. To complete the model, an earthen mesh was inserted between the stones to underline the effect of reality. At last an horizontal plane was placed to simulate the pavement and the terrain, modeled with sub surf, smoothing, displacing and decimate tools. For what regard the building B, its plan was used to obtain the rough outline of the models, and the location and shape of the upper visible stones. Instead of manually drawing all the stones one by one it was preferred to use a displacement modifier on a grid, using an height map obtained from the survey. This has been later decimated using the open source mesh editing program Meshlab developed by ISTI-CNR, Pisa. As the precincts were basically composed of earth and stones, two equal

Fig. 1: Buildings A and B during the excavation.

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and separated models were produced and then intersected and meshed in order to obtain the same building technique. While the vast majority of the recent works belonging to this field used photographic textures for their reliability respect to light conditions and availability, in this case were preferred procedural textures for almost all materials, because of the ease of use when applied to complex meshes such as the groups of stones the buildings are made of.

Besides the structures, two votive deposits were chosen for the realization of a 3D model on the basis of direct observation of the archaeological site, the deposit 1 for building A and deposit 6 for building B. The original positions of the objects were located on the basis of photographic and graphic documentation taken during the excavation.

The deposit 1 of building A (Fig. 2)consisted of one oinochoe, an iron sickle and an elaborated necklace composed by clay, amber, and bone globular beads. In this case, the texture were created starting from photographic images of each objects and pictures taken on site. Through graphic software an image that could represent the entirety of the models was created. The occasional information deficiency was filled sticking with stylistic data. For the modeling the sculpt mode was used in order to obtain a closer and finer reconstruction. Differently from other finds, about the necklace, procedural textures were used to better represent amber and bone. The items of the votive deposit 6 of building B were four vessels, three oinochoai and one bowl, two small ivory heads belonging to small statuettes, an iron spear head and a bone hairpin. For the modeling, the principal volumes were extruded by modeling the extra parts, starting from these drawings, The textures were obtained from stereoscopic pictures combined in a unique scheme and then applied to every model. A procedural texture was also applied to the virtual vessels in order to generate a normal mapping.

As the virtual recreation of all the monuments of the Polizzello Acropolis is a still ongoing research of Archeomatica project (www.archeomatica.unict.it), the 3D models of each building was realized in different times. In this case, Building B model was developed in 2008 by E. Sangregorio and Building A in 2009 by an equip work of A. Fiamingo, E. Greco and R. Urso. The two projects were meshed together and placed in the same virtual environment in order to

Fig. 2: Deposit 1. From left to right, a necklace, fragments of an oinochoe and an iron sickle.

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create screenshots and videos. The landscape has been modeled using the height values of the acropolis, textured with a mixture of procedural grain and sand and enriched with L-System generated trees and other flora. Fraxina veluta for trees and Mediterranean flora, currently present on the Polizzello Mountain, were recreated, because of the lacking of archaeo-botanical studies on site. This preliminary work, part of a much more complex and articulated project of recreating the past, aimed to demonstrate the expressive power of 3D modeling applied to the conservation and fruition of cultural heritage. This type of representation allows a better and faster comprehension of the site offering virtual benchmarks for the archaeologists’ interpretations.The next step is to improve the rendering graphic, explore new fruition ways as, for example, interactive applications focusing in particular on the lightweight for the web. Furthermore the are models, still on developing, will be realized and merged in order to obtain a virtual replica of the Polizzello Acropolis, as it is now and as it was during the phases of its past life. In fact, one goal is to produce a multi-phase model representing the evolution of the area, the changes carried to the buildings and the exact arrangement of the archaeological finds, always focusing on the philological approach that distinguish the project.

ACKNOWLEDGEMENTS

The authors gratefully thanks professors Filippo Stanco and Davide Tanasi, scientific directors of the Archeomatica Project, for the permission to carry out this study.

Fig. 3: Final 3D renders. Figures a and b: Buildings B and A, panoramic view; figure c: Deposit 6, inside Building B; figure d: Deposit 1, inside Building A.

a

c

b

d

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