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1) Aim of the research

2) State of the art

 

 

 

1) Aim of the research

First aim of the search is the reconstruction of the virtual shape of an archaeological find through the management, on CAD system, of information obtained from the analysis of available fragments. This objective demands the setting up of a methodology, supported by computer science systems, for the acquisition, by means of automatic machine of measure, of relative geometrical data to the lower surface and the upper wing surface of the elements of surface of fragments. With a limited number of measure points it is possible to obtain the definition, sufficiently near the truth, of the surface that envelops them. Moreover, it is possible to employ, beyond that the traditional techniques, also techniques of scansion with scanner 3d laser or television cameras in order to optimise the times or to improve the virtual reconstruction of the object of perfect shape.

A second aim, connected to the first one, is the development of a classification system and coding of the characteristics of the fragment. That particularly demands to considerate the geometric nature of the two surfaces, the inner and the external one, and of the main characteristics of the thickness that, as an example, could be its main value and its maximum variation percentage. These data, joined to those of descriptive type that the experts of archaeology will suggest to take in consideration, will be the base of the classification and coding system by means of which, with an appropriate algorithm the rebuilding of fragments pertaining to the same object or the same productive technology could be operated. The resetting operation, in particular, could be made easier from the comparison with virtual elements gathered from the analysis of intact or already restored objects and inserted in the classification system in order to act as guide elements of the selectioning algorithm.
The rebuilding of fragments could therefore be operated at first in virtual way, using the parametric capabilities of employed CAD system that will follow an algorithm of genetic type in order to define the shape that better draws near the external or inner surface of the object.

The third objective, in fact, coming out from the definition of geometry, consists in the construction using Rapid Prototyping (RP) techniques, of the virtual object. All that to reach the definition of the inner surface of the object which functions as external surface to the supporting model of the real fragments that will be rebuilt after the necessary cycles of analysis and synthesis to obtain, with the best approximation, the shape of the report to restore.
The file relative to the digitised model of the approximate inner surface of the manufacture to reconstruct can in fact be directly transferred to the RP equipment. It is employed in order to generate the model in resin to employ as support surface of the fragments that on it will be fixed with suitable glues, before in temporary way and therefore, after the necessary replies, in definitive shape.

 

2) State of the art

The present proposal is originated from the crescent interest that the archaeologists recall in a generalised manner in relation to their valorisation like fundamental economic resource of the Italian territory and in particular of the southern region. In the southern territory, that corresponds in great part to that one of the Magna Greece, in fact, There are the signs of the civilisations that have marked the more flourishing periods of the history. It is thought of fundamental importance to bring a methodological and technological contribution to the valorisation, through the recovery, the classification and the restoration, of this huge patrimony. The technologies, today available, whose employment is shown here, are in a position to bring a substantial contribution to the irreplaceable and passionate work of the archaeology experts. The present proposal must be considered a contribution to the cause of archaeology in the spirit of the multidisciplinary co-operation that is the only approach that concurs, in the diversity of the roles, the most effective valorisation of the specific competencies.

The job that the archaeologists carry on, at first previews the collection and the classification of fragments recovered during the dig, and therefore it demands the reassembly and the reconstruction of the original objects from which they come.
Sometimes there are very small fragments (also of the order of magnitude of ten millimetres) that, with a manual and laborious procedure are in first, cleaned up and classified for zone of recovery, thickness, colour, quality of the paste and therefore for shape. Subsequently it proceedes to the aggregation of the fragments that are judged pertaining to the same find and, therefore, they pass to the definition of the shape of the original object through the acknowledgement of the curving by means of the employment of opportune characteristic shapes and of the resemblance to already known archetypes. The experience, the sensibility and the acquaintances of the researchers engaged in a such kind of job produced permit to reconstruct an object destroyed many centuries before, replacing the numerous fragments. All the described operations are conducted manually. The acknowledgement of the shapes and the attribution of the qualitative parameters are only fruit of the acquaintance and the subjective experience of the operator.

Even if subsequently it has been done a certain progress because the phase of classification and of acknowledgement of fragments, with the purpose to recompose the single objects, has been managed, by means of an appropriate program, with the aid of the computer, other systematic applications of the computer science technologies are not still diffusely employed. After recent but episodic applications, of the solid modelling and the rapid prototyping to the reconstruction or the duplication of particular works of art, it comes the consideration that would be today possible to co-ordinate and apply to all the available experiences and to obtain very important results integrating, in an only procedure, a series of techniques and technologies.
Great part of such acquaintances constitutes a cultural patrimony, within the disciplinary area of the Drawing and Methods of the Industrial Engineering.

The present plan of search foresees, moreover, the use of multiple computer-aided systems and therefore the necessity to guarantee the continuous transmission of information. The management of reference protocols for data exchange is integrating part of the present job in object.
The actual studies lead on the problematic dealing with data exchange between CAD systems, by means of neutral translators (IGES, STEP), have evidenced which problems are in the transfer of the surfaces constructed in different ambits of development (each characterised from a specific inner format of system) , to different ambits of use (virtual reality, rapid prototyping). A Correct data exchange of the surfaces demands a particular attention to the parameters of accuracy (that control the generation of geometry) and to the zones of connection between different "patches" of surfaces (presence of gap or overlapping).
For the individuation and the correction of eventual errors and inaccuracy of the geometry, object of a reconstruction or an operation of transfer, will be used CAD systems more advanced or " dedicated " to the management of the surfaces.

 

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