The use of laser scanner and data processing of the data has significant applications in the digital restoration of individual archaeological artifacts, also for what concerns the clarification of certain technical or artistic features. A case study of this type was represented by the analysis on a portion of female torso in marble, dated between the middle and late Roman Empire (II-IV century AD), found in the excavations in the courtyard of the church of St. Agata la Vetere in Catania (Figure 1.18). The bust of 32 x 18 x 11 cm, headless, retained only the left half, missing arms and the torso was preserved in the upper part. Near the sternum was evident that a sharp slit resulted in a lack of left side. Considering that the level of the excavation from which it came was related to a landfill and then the bust was not in primary position, its condition and typology seemed to be unusual. To better document the signs of working and to try through the modeling of 3D virtual models to propose a more precise interpretation, it was decided to acquire the bust with a laser scanner and then to operate on the model in Blender environment. The study and examination of the part under the cut, highlighted, in addition to signs of a progressive series of smoothing, the presence of a deep cut with a shallow central hole for housing a nail. The hypothesis was that the artifact was a kind of architectural applique in the form of semi-female bust; it would seem, however, refuted by the fact that the hole for the nail is very shallow and not sufficient to ensure a firm grip with a masonry wall. Furthermore, as the section is not vertical but curvilinear it is not possible to suggest any other hypotheses of reconstruction. A second hypothesis, more plausible, is that the bust was part of an acrolith of marble and wood, parts of which were made with small pieces of marble for reuse; this could justify the lack of depth and shape eccentric of the nail, which in this case would grip the wood. The analysis on the 3D model of the compatibility of the contact surfaces in the proximity of the neck and between the breasts, shows that probably the artifact was composed by two half parts. In this case the hole for the plug would serve for a short nail that would clamp the two halves of the trunk between them. The peculiar shape of the chest can be justified suggesting the insertion of the wooden part of the acrolith, that also determined an uncommon chromatic effect for the Late Roman empire sculpture.
(a) Late Roman marble female torso from the excavation at St. Agata church at Catania; (b) phases of study and restoration analysis in virtual ambient of the torso acquired with laser scanning technique.
This case is a true virtual replication of an architectural or archaeological reality aimed to preseverve its condition before undergoing inevitable changes of time or human work. For these reasons, the technique of digital restoration finds wide application especially in the field of urban archeology where the stratification, the continuous building activity, and reduced chance to maintain accessible the discoveries become recurring features. In this perspective, the research carried out by the team of Archeomatica Project is set, in relation to some evidence emerged during archaeological excavations in Catania, between 2002 and 2005, in the complex adjoining the churches of St. Agata la Vetere  and St. Agata al Carcere , in the heart of downtown, where a continuous stratigraphy articulated from the Late Hellenistic period to the Middle Ages was identified . Surveys held in conjunction with restoration of the two churches have revealed numerous monumental emergencies that were restored and preserved but, after the end of the works and the returning to the worship of the two buildings, cannot be showed to the public. During exploration , the most significant discovery was done in the sacristy of the Church of St. Agata al Carcere. Here, just below the modern pavement, in the midwest part, an accumulation of large rough blocks that seemed to follow a north-south alignment was unearthed (Figure 1.19(a)). The first hypothesis was that this accumulation was the result of the collapse of a great wall structure. It had an appreciable width of 2.25 m and a length of 2.80 m. The irregular blocks of lava stone of huge dimension were set as double curtains of a large wall filled with emplecton technique. It can be compared to other polygonal archaic walls dating from the first half of the sixth century BC, found in nearby excavations near the former Reclusorio della Purita, inside the Roman theater, and in the cloister of the Benedictine monastery . With the deepening of the investigation, in a small hole, filled with ashes and a few minute burnt animal bones, were found in situ, 2 two-handled olle and large two-handled stamnos with discoid lid, which suggest a chronological framework in the second half of the third century BC (Figure 1.7.4). This thysia finds comparisons in other part of the city, such as excavation yet unpublished at Palazzo Sangiuliano, or more properly as in the above-mentioned complex of Reclusorio della Purita [113,114], where there were found some votive pits dug into a pavement related to polygonal wall, containing two-handled olle and ashes.
(a) Hellenistic votive deposit from the excavation at St. Agata church at Catania, at the moment of the discovery; (b) 3D models of three vessels of the votive deposit obtained with laser scanning technique; (c) virtual model of the excavation area depicting the discovery conditions of the votive deposit obtained integrating laser scanning and 3D modeling techniques.
This Hellenistic depositional practice is well documented also in Syracuse in the sacred area near Altar of Hiero II . For the Catania context, this means that in the Hellenistic age the ruins of the archaic city were still visible and considered sacred as to perform specific rituals related to them, rituals of remembering the ancient tradition of the city. To better analyze this significant evidence, extrapolating from the rest of the architectural complex, it was decided to operate the digital restoration of the environment of the sacristy, of the ruins of the ancient city wall, and of the Hellenistic deposition, using a hybrid technique, the 3D modeling in Blender environment for the walls and the laser scanning for the vessels of the deposit. The integration of the two techniques has allowed, on one hand, to assess the strengths and weaknesses and opportunities of integration and on the other provided a virtual model that offers a snapshot of the Hellenistic depositional area on the ruins of the Archaic wall, as it was when it was used.
Dealing with Image Data in Archaeology: New Perspectives
The future of virtual archaeology and of its applications in the field of research and promotion of archaeological goods seems to be linked in an unavoidable way to the evolution of the virtual reality (VR) environment . The virtual reality allows the 3D visualization of concepts, objects, or spaces and their contextualization through the creation of a visual framework in which data is displayed. VR also enables interaction with data organized in 3D, facilitating the interaction between human, data, and information in order to enhance the sensorial perception . It creates a virtual space that is a replica of the real space, where the information about every feature that constituted the different moments of life of the real space are “translated” in 3D data. The two crucial points of every project of VR are the selection of the informations (pictures, drawings, geometrical measures) and the choice of which facet of the original object’s nature must be captured and reconstructed. “Visual computer models should make clear their sources and the criteria on which they are based” .
From this point of view, VR is not a copy of the “reality,” but the representation of “one,” or, several “instances,” possibilities among others, various under different circumstances and contexts, even if it can offer a multilayered reality experience, a kind of digital surrogate of the real world . It has the cohesive function of relating the raw data to the interpretation  and “the ability to get inside and walk around the reconstruction buildings gave a stronger feeling of enclosed space and volume, and enhance the sense of being there” . The most important limit in the mimetic ability of the past and present reality of the VR is, in fact, represented by the cultural formation of the authors of the project, that in many cases are archaeologists. Diverse point of view can, in fact, affect the selection of the informations and produce very different results in terms of visual image of the past . In order to understand archaeological systems, much more than a visually “realistic” geometric model is needed. “Dynamism and interaction” are essential. A dynamic model is a model that changes in position, size, material properties, lighting, and viewing specification. If those changes are not static but respond to user input, we enter into the proper world of virtual reality, whose key feature is real-time (RT) interaction. Here real-time means that the computer is able to detect input and modify the virtual world “instantaneously” at user commands. By selectively transforming an object, that is, by interpolating shape transformations, archaeologists may be able to form an object hypothesis more quickly . The next step, on the same research direction, is the realization of systems of virtual experience of the recreated past, beyond the physical limits of the personal computer. “To make an archaeological excavation simulation compatible with the dynamics of the learning environment, the user must be able to navigate within it without being entirely bound to specified pathways, as typified by menu-driven routines or the buttons and links of a hyperspace environment” . One field where the scholars in archaeology and computer science are recently getting involved is augmented reality (AR) or enhanced reality (ER) environments. Augmented reality has been defined as the simultaneous acquisition of supplemental virtual data about the real world while navigating around a physical reality . In an AR environment the computer provides additional information that enhances or augments the real world, rather than replacing it with a completely virtual environment . One of the objectives of AR is to bring the computer out of the desktop environment and into the world of the user working with a three-dimensional application. In contrast to VR, where the user is immersed in the world of the computer, AR incorporates the computer into the reality of the user. The user can then interact with the real world in a natural way, with the computer providing information and assistance. It is then a combination of the real scene viewed by the user and a virtual scene generated by the computer that augments the scene with additional information. The virtual world acts as an interface, which may not be used if it provides the same experience as face-to-face communication. AR enables users to go “beyond being there” and enhance the experience in order to achieve both the full interpretation of the traces of the past and the developing of the best tool for the dissemination of their message . An example of the potential of this technology applied to archaeology is the augmented reality-based cultural heritage On-site Guide, acronym ARCHEOGUIDE, that provides new ways of information access at Greek archaeological sites in a compelling, user-friendly way through the use of 3D-visualization, mobile computing, and multi-modal interaction [126,127]. The potential of this approach in the future could be enhanced by investing much more in the five fundamental elements of an AR environment, namely virtuality (objects that don’t exist in the real world can be viewed and examined), augmentation (real objects can be augmented by virtual annotations), cooperation (multiple users can see each other and cooperate in a natural way), independence (each user controls his own independent viewpoint), and individuality (displayed data can be different for each viewer) . In conclusion, the encouraging results of the application of the computer graphics 3D to the archaeological evidence has demonstrated that it is possible to use another “sense” do decrypt the traces of the past: three-dimensional recreation of ancient life and visual images are extremely effective in explaining the past because they allow us to experience it.