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The aim of this research is to suggest a methodology based on 3D survey and reconstructive modeling, suitable to increase the actual knowledge of an historical building and supporting its historical interpretation. The case study used for testing the proposed methodology is the huge Chartreuse of Pavia, with a special focus on a relatively unexplored portion of the monument. The survey, based on 3D laser scanning and orthoimages, integrated by historical studies and other complementary information (thermoluminescence dating, IR imaging, hystorical analysis), allowed to read all the architectural aspects hidden in this highly architecturally stratified monument, improving in this way the comprehension of the building’s transformations in time. A 3D reconstruction approach was then suggested, merging several information of different nature, from the actual geometry of the building to the interpretation of historical documents, suggesting a sequence of diachronic models as virtual narration of the historical evolution. On other hand the 3D models were used to obtain a cross-validation of the historical evolution hypotheses developed by experts in the various disciplines involved in the project. The data collected were exploited through a web portal in order to enhance the readability of tangible and intangible heritage associated to that Chartreuse portion, nowadays not accessible to common public

ABSTRACT:The methodology proposed in this paper in based on an integrated approach for creating a 3D digital reconstruction of an archaeological site, using extensively the 3D documentation of the site in its current state, followed by an iterative interaction between archaeologists and digital modelers, leading to a progressive refinement of the reconstructive hypotheses. The starting point of the method is the reality-based model, which, together with ancient drawings and documents, is used for generating the first reconstructive step. Such rough approximation of a possible architectural structure can be annotated through archaeological considerations that has to be confronted with geometrical constraints, producing a reduction of the reconstructive hypotheses to a limited set, each one to be archaeologically evaluated. This refinement loop on the reconstructive choices is iterated until the result become convincing by both points of view, integrating in the best way all the available sources. The proposed method has been verified on the ruins of five temples in the My Son site, a wide archaeological area located in central Vietnam. The integration of 3D surveyed data and historical documentation has allowed to support a digital reconstruction of not existing architectures, developing their three-dimensional digital models step by step, from rough shapes to highly sophisticate virtual prototypes.* Corresponding author. This is useful to know for communication with the appropriate person in cases with more than one author. INTRUDUCTIONReconstructing ancient buildings and cities from their remains has been one of the main applications of computer graphics in Archaeology for its suggestive potential. Behind a generic imaginative effect that might be considered fake or purely spectacular by purists of the archaeological science, in several cases it has been demonstrated that seeing a reconstructed artifact in a realistic simulated context, may allow obtaining new archaeological discoveries. As shown by some authors (Frischer and Dakouri-Hild, 2008), the visualization of actual shapes and their geometrical relationships with the contextonly explained in verbal form in a traditional approach -may act as a trigger to imagine novel scenarios. On the other hand, the logical path leading from an archaeological site to a reasonable reconstructive hypothesis is full of pitfalls that can lead to multiple solutions, even very different from each other due to multiple levels of interpretation of the historical sources that can be used for such purpose. The problem, already quite complex when considered in the two dimensions of the buildings footprints, is further complicated when the third dimension of the elevations, generally much less documented in the historical sources, is added. The many experiments conducted in the past twenty years have been anyway conducted in large majority on available sources and existing surveys rather than facing the problem as a multidisciplinary problem, as it is. This paper tries to focus wh...

In the past 20 years, several methods have been proposed for re-coding 3D models with a low-spatial-frequency 3D representation plus a high-frequency 2D map for recovering the details. This approach has been explored with different kinds of mapping (bump, normal, relief, parallax, displacement), which have been shown to be effective in dramatically reducing model size while still maintaining a good visual appearance. For this reason, these approaches are widely applied in those situations where the rendering time constraints are critical (e.g., real-time rendering of complex models for gaming). However, the significant difference between the original detailed 3D model and the re-coded version has made it impossible to consider the latter as a metrically satisfying substitute for the former. The purpose of this article is to propose a re-coding method based on displaced subdivision surfaces that makes it possible to adapt the re-coded 3D representation to the metrological limitations of the 3D capturing technique used for generating the original mesh. In this way, it is possible to keep the geometric incoherency between the re-coded and the acquired mesh below the threshold determined by the natural capturing technology uncertainty. The resulting re-coded model can be therefore considered as close to the physical object/scenario, as the original acquired mesh, with a great advantage in terms of 3D representation size, UV parametrization, topological coherence, and scalability. The method has been tested on three cultural heritage objects with different complexity: a damaged wooden painting by Leonardo da Vinci (a nearly 2.5D shape), a Roman stone head sculpture (full 3D shape with simple topology), and a full body bronze sculpture by Donatello (full 3D shape with complex topology), demonstrating the coherency between the re-coded models and the originals, with a model size compression depending on the topological complexity that may reach a level of better than 1:25.

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