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Despite what might be assumed, the surface of a painting on a canvas or a wooden panel is not perfectly flat, but rather is characterized by a complex three-dimensionality. The paint the artist lays down on the support possesses its own body and thickness, that, even on a millimeter or sub-millimeter scale, may be detected using instruments and three-dimensional measurement applications. At the same time, a wooden panel may be affected by deformations from historical or restoration changes, which may be readily revealed and documented. When analyzing a work of art subjected to an important restoration treatment, as was the case of the Adoration of the Magi by Leonardo da Vinci, a precise 3D documentation of the painted surface is thus strictly linked to the state of its wooden support. As is well-known, a panel painting is a layered structure (usually a protective varnish coating, paint layers, usually preparatory or ground layers, and the wooden panel), each with different physical and chemical compositions. Therefore, an accurate geometric 3D acquisition of the board structure and its connecting components (butterfly joins or dowel inserts) and the auxiliary support system (crossbars) may supply information to not only improve understanding of how the painting was made and its condition, but also permit it to be monitored over time or during restoration. Furthermore, the application of modern 3D computer graphics technologies is not only a valid diagnostic aid to acquiring knowledge about the work, but also a way to map information and share it (for example art historical information, technical data, and the results of chemical and physical analyses), making them easily accessible online both to experts in the sector and a wider public, thanks to specifically developed multimedia systems.1 In the case of the unfinished masterpiece by Leonardo, a complete high resolution 3D acquisition was performed in order to show and measure--at the moment during conservation treatment--a map of deviations from planarity caused by the curvature and warp of the wooden boards, permitting the documenting of the spatial deformation of the painted surface and the monitoring of its state of preservation.

Tra le analisi diagnostiche non invasive effettuate in supporto al restauro della tavola raffigurante Papa Leone X de' Medici tra i cardinali Giulio de Medici e Luigi de' Rossi di Raffaello è stato eseguito un rilievo tridimensionale (3D) dell'intera opera. Il rilievo 3D, oltre ad essere usato per effettuare misure sulla forma della superficie ed essere un valido supporto per la conoscenza e lo studio dell'opera, si configura anche come un efficace mezzo per monitorarne lo stato di conservazione nel tempo. In questo caso, l'acquisizione 3D era volta alla valutazione della deformazione del supporto ligneo e allo studio del deterioramento della superficie pittorica. Per tale motivo l'intera opera (fronte, retro e bordi) è stata acquisita con un passo di campionamento medio pari a 0.3 mm. Alcune zone sono state acquisite anche ad una risoluzione di 0.16 mm al fine di mettere a punto un metodo automatico in grado di evidenziare le micro-fratture dello strato pittorico.

Le tecniche di digitalizzazione 3D si sono fatte largo prepotentemente nel campo dei beni culturali. Dalle prime sperimentazioni dell'utilizzo di modelli 3D di due decenni fa, si è arrivati oggi ad una ampia diffusione e democratizzazione di queste tecnologie, fino a poter dire che la digitalizzazione 3D è uno strumento ormai essenziale nella maggior parte dei progetti di conservazione, restauro, documentazione e studio dei beni culturali. Nell'ultimo periodo, poi, anche le tecnologie di riproduzione fisica da modelli 3D (3D printing e la prototipazione rapida) stanno entrando nella routine di queste tipologie di azione. Un aspetto chiave dei modelli digitali 3D risiede nella loro "doppia natura": -i modelli 3D sono pura informazione numerica e geometrica, sono fatti, cioè, di numeri che rappresentano le misure e la forma di un oggetto fisico. Hanno dunque proprietà metriche, e le misure in essi contenute possono essere usate per calcoli tecnici, documentazione, simulazione e riproduzione fisica; -i modelli 3D però hanno anche un aspetto "visuale", cioè possono essere visualizzati e disegnati a schermo formando immagini che, visivamente, corrispondono alla percezione che noi avremmo davanti all'oggetto reale (specialmente quando il modello 3D geometrico è corredato anche di informazione di tessitura o colore). Questa doppia natura unisce una precisione, una scientificità del dato, alla possibilità di interagire con esso in maniera naturale, come faremmo con l'oggetto reale. Se è vero che nelle prime sperimentazioni, i modelli 3D sono stati utilizzati solamente come fonte di misure e di dati, oppure solo come "gadget visuale" per presentare al pubblico l'oggetto d'arte, possiamo dire che oggi, con il progredire delle tecnologie, e soprattutto con la definizione di protocolli di lavoro più completi, questi due aspetti riescono ad essere sfruttati appieno in maniera congiunta. In questo lavoro, per l'appunto, è stato possibile sfruttare appieno le potenzialità del media digitale 3D, sia dal punto di vista scientifico-documentale, che come strumento di disseminazione e di coinvolgimento del pubblico.

Un dipinto su tela o su tavola, contrariamente a quanto si potrebbe pensare, non è un oggetto con una superficie perfettamente planare, ma è caratterizzato da una complessa tridimensionalità. Il colore che l'artista pone sul supporto ha una propria corposità materica, uno spessore, che, seppur millimetrico o sub-millimetrico, può essere rilevato con strumenti e applicativi di misurazione tridimensionale (3D). Allo stesso tempo, il supporto ligneo può presentare deformazioni legate a vicissitudini storiche e conservative, che possono essere facilmente rilevate e documentate. Nella fase di analisi di un'opera soggetta ad un importante intervento di restauro, come è avvenuto per l'Adorazione dei Magi di Leonardo da Vinci, un'accurata documentazione 3D della superficie pittorica è pertanto strettamente legata a quella del suo supporto ligneo. Pertanto, una scrupolosa acquisizione geometrica 3D del tavolato e dei suoi elementi di collegamento (farfalle e cavicchi) e di sostegno (traverse) può fornire elementi utili non solo per una maggiore conoscenza della fattura dell'opera e del suo stato di conservazione, ma anche per un suo monitoraggio nel corso del tempo o in fase di restauro. Inoltre, un uso appropriato delle moderne tecnologie di Computer Grafica 3D non rappresenta soltanto un valido ausilio diagnostico per la conoscenza dell'opera, ma anche un mezzo per raccogliere informazioni di carattere scientifico-divulgativo (ad esempio dati storico-artistici, tecnici, risultati di analisi chimico-fisiche) e renderle facilmente fruibili on-line agli addetti del settore e ad un pubblico più vasto, grazie a sistemi multimediali appositamente sviluppati. Nel caso del capolavoro non concluso di Leonardo, una sua completa acquisizione 3D ad alta risoluzione è stata eseguita con lo scopo di evidenziare e misurare - in fase di restauro pittorico - una mappa di deviazioni della planarità causata dalla curvatura e deformazione delle tavole lignee, consentendo di documentare la deformazione spaziale subìta dalla pittura e monitorare il suo stato di conservazione.

Il progetto ArTeSalVa ha preso in considerazione con un approccio multidisciplinare il patrimonio immobiliare pubblico di interesse storico-artistico, dedicando particolare attenzione ad alcuni edifici di notevoli dimensioni e in attuale condizione di sottoutilizzo presenti nel territorio toscano. L'obiettivo è stato quello di rimettere al centro del dibattito pubblico alcuni grandi complessi immobiliari, per interrogarsi sul loro futuro a partire dalla conoscenza della loro storia. Il presente volume offre un approfondimento sulla Badia Camaldolese di Volterra, non solo sulle fasi costruttive ed espansive, ma anche su aspetti forse meno indagati, come le frane, le alterazioni d'uso e il lungo dibattito otto e novecentesco sui modi di protezione e salvaguardia del complesso.

Il volume, esito del Progetto Artesalva (POR-FSE Regione Toscana 2007-2013), offre una riflessione sul tema del riuso, prendendo spunto da singoli esempi presenti in Toscana, riferibili a diverse tipologie architettoniche e a funzioni differenziate. Tra i casi analizzati la Certosa di Calci (Pisa), un complesso monastico certosino abbandonato dai padri negli anni Settanta del Novecento e oggi sede di due musei; la villa medicea L'Ambrogiana di Montelupo Fiorentino (Firenze), trasformata alla fine dell'Ottocento in manicomio e poi in ospedale psichiatrico giudiziario; la Rocca delle Verrucole a San Romano in Garfagnana (Lucca), sottoposta a partire dagli anni Ottanta del Novecento a interventi di recupero.

A very large number of sites, probably the large majority of our Cultural Heritage (CH), are unaccessible to the public due to the lack of infrastructure, improper security conditions or lack of personnel. Digitizing in 3D those sites is not very complicated nowadays. We will briefly review the technology available for cheap 3D digitization, from 3D scanning to cheaper photogrammetric solutions. However, digitization per se is not a solution: 3D models have to be shared in the widest and easiest manner. We will present the design and results of a software instrument that aims at supporting easy navigation of 3D digitized spaces, running on top of mobile devices such as tablets or smartphones. The main goal of this project is to guarantee navigation with ease for users without experience in computer graphics and videogames, while providing high-fidelity rendering of the digital 3D model.

Our age is characterized by the ease of communication and fast and free exchange of data. The use of standards and a common approach to recollect, organize and present the documentation gives a great advantage for the knowledge and dissemination of the archaeological, artistic, historical and conservation information of Cultural Heritage. Establishing a "correct" documentation policy is the main goal that guided our initiative for the documentation, preservation and valorisation of the monumental complex of the Camaldolese Abbey in Tuscany. In this project we retrieved the paper documentation in the Historical Archives of the Tuscany Region, to study the historical and conservation data of the monumental complex. Digital technologies have been used to support storing and access to this important information, including also data to monitor the current state of its preservation. The documentation has been digitized and is accessible through a web database; this resource was designed by following the Italian National standards proposed by Central Institute for Cataloguing and Documentation (ICCD). The current state of conservation of some parts of the building has been documented by taking panoramic images or panoramas (360º images) and by the acquiring 3D digital models. In particular, panoramas are used to document the state of preservation of frescoed rooms, while geometric 3D models are produced to document the degraded areas of the church, which require a constant monitoring. Moreover, an analytical virtual reconstruction of the church was modeled to depict its status before the building's collapse. The main goals of this work are to provide a good-practice example on how to document and disseminate on the web the knowledge available on an endangered monument, following national and international standards, in order to make the knowledge widely accessible. In this way, it is possible to disseminate and enhance the old results with new analysis and interpretations of documents that can be easily shared with other researches, conservation experts and the ordinary public.

The chapter of the book "La Badia Camaldolese Volterra" reports the results obtained to the knowledge of preservation history of the Abbey church, through a deepening and integration of different knowledge fields. For this purpose, we have been used different data acquisition procedures, which have been specifically chosen to the investigated ancient building. They are supported through the study of historical and architectural features of the structure. This knowledge process was followed by a data processing step in order to manage and visualize the achieved results.

The Italian historic architectural heritage includes a special and widespread category of buildings: the fortresses. Fortresses characterized for centuries the image of many Italian towns and landscapes and their presence modelled their urban or rural settings. Today these military buildings have lost their original function and very often create difficulties in current urban policies, in consideration of their dimensions, their collocation and the high costs for their preservation. As consequence, they are often in critical conditions of conservation and they have been frequently transformed in empty spaces disconnected from the current city life. The better way to protect these huge architectures consists in a long-term planning of sustainable reuse. Obviously these structures cannot be used to fulfill their original military functions and their peculiar architectural features clash sometimes with actual needs. It is necessary to study each structure according to its environmental, social and cultural contest to facilitate its best reconversion. The use of multimedia instruments suggests a method to reach satisfactory results but also it engenders some questions and doubts. The goal of this paper is to analyze the problem of fortresses today and to explain some meaningful cases of reuse in central Italy. Particular attention will be paid to the fortress of Verrucole near Lucca. This is an emblematic case study both for the choices of restoration and new display and for the difficulty to select new functions.

The "ArTeSalVa" project starts from the observation of the neglect and disuse of the historical public buildings in Italy, which have important architectural value. The project aims at studying the less known historical events regarding some decaying buildings in Tuscany and using 2D and 3D digitization modalities in order to map the current status, to track decay processes and to create effective tools for scientific and tourism visual communication. A significant case study is represented by the medieval Carthusia, in Calci near Pisa. The his-torical research is investigating the different ways in which the monastery was used and thus the most important changes introduced in it. The related digitized data are used to record the decay, highlight transformations and support planning of possible new uses of the areas that are not currently accessible to the public. The digital models are the instruments to document and present visually the scientific results.

This paper describes the main phases of an ongoing project regarding the 3D virtual reconstruction of an Etruscan hypogeum together with the funerary equipment it contained. The tomb is dating back to late Hellenistic period. It was discovered in 1880 in Sigliano, between lake Trasimeno and lake of Chiusi in Central Italy. This sepulcher is a paradigmatic testimony to enlighten the processes of settlement and land use during ancient times in a district (Valdichiana) with a strong vocation for agriculture and forestry. Furthermore, this reconstruction allows to relocate in their original context some finds now kept at the Archaeological Museum of Perugia, together with some other lost goods, documented by detailed sketches and drawings only. Hence, 3D modeling and 3D scanning have been combined to present the plausible appearance of the tomb when it was discovered. Some of the most interesting objects have been 3D scanned to provide accurate data. Particular care has been devoted to the 3D model of a probably gilded bronze helmet, a Southern Italy production (probabl y from Taranto) dated 4th century BC. A portion of plausible landscape has been modeled taking into account the geomorphology obtained through Google Earth, to locate the grave, and to insert it in a possible context. Moreover, following the indications found in the original sketches, the interior of the tomb and some of the smaller objects have been modeled. All of the generated data have been used to produce a video which will be shown at the Archaeological Museum of Perugia.

Le tecniche di visualizzazione grafica tridimensionale accoppiate alle più recenti metodiche per il rilievo delle caratteristiche di forma e colore aprono notevoli possibilità di analisi, studio e documentazione nel settore dei Beni Culturali 2. Come emerso dai precedenti contributi è oggi possibile campionare la superficie di un'opera d'arte in modo molto accurato e con una risoluzione spaziale molto alta (si parla in entrambi i casi di valori dell'ordine di pochi micron), ottenendo modelli tridimensionali estremamente fedeli all'originale 3. Inoltre, e' oggi possibile acquisire informazioni sulle modalità con cui la superficie stessa riflette la radiazione luminosa, sia acquisendo la luce riflessa sulle varie bande 4 che rilevando come diverse direzioni di incidenza siano riflesse nelle varie possibili direzioni di riflessione (Bi-directional Reflectance Distribution Function, BRDF). In questa sezione vedremo come tale informazione possa essere integrata e fruita dallo studioso per mezzo di uno strumento di visualizzazione 3D.

In this paper we describe the virtual reconstruction of a dismantled and dispersed piece of art: the Funerary Complex of Arrigo VII. To faithfully reconstruct the monument, all of the statues and elements of the mausoleum have been acquired in digital 3D format; then, with advanced computer graphics techniques, some of the accredited reconstructing hypothesis have been assembled and evaluated.

Range map registration is still the most time consuming phase in the processing of 3D scanning data. This is because real scanning sets are composed of hundreds of range maps and their registration is still partially manual. We propose a new method to manage complex scan sets acquired by following a regular scanner pose pattern. Our goal is to define an initial adjacency graph by coarsely aligning couples of range maps that we know are partially overlapping thanks to the adopted scanning strategy. For a pair of partially overlapping range maps, our iterative solution locates pairs of correspondent vertices through the computation of a regular n×n kernel which takes into account vertex normals and is defined in the 2D space of the range map (represented in implicit 2D format rather than as a triangle mesh in 3D space). The shape-characterization kernel and the metrics defined give a sufficiently accurate shape matching, which has been proven to fit well the requirements of automatic registration. This initial set of adjacency arcs can then be augmented by the automatic identification of the other significant arcs, by adopting a criterion based on approximate range map overlap computation. With respect to the solutions present in literature, the simplifications and assumptions adopted make our solution specifically oriented to complex 3D scanning campaigns (hundreds of range maps). The proposed method can coarsely register range maps in parallel with the acquisition activity and this is a valuable help in assessing on site the completeness of the sampling of large objects.

The construction of detailed and accurate 3D models is made easier by the increasing diffusion of 3D scanning devices. These allow to build accurate digital models of real 3D objects in a cost- and time-effective manner. The talk will present the capabilities of this technology focusing mainly on some issues which are preventing its wider use, such as the considerable user intervention required, the usually incomplete sampling of the artifact surface and the complexity of the models produced. Another emerging issue is how to support the visual presentation of the models (local or remote) with guaranteed interactive rendering rates. Some examples of the results of current projects, mainly in the Cultural Heritage field, will be shown.

The paper presents the results of a 3D scanning campaign which sampled both the exterior facades of an ancient Basilica in Torcello (Venice, Italy) and some key elements of its interior. The targets of our scanning project were selected to be representative of different subjects, requiring different digital sampling technologies. We have used a range of scanning devices: a triangulation scanner for medium scale artifacts, a phase-modulation time-of-flight device for larger surfaces (mosaics), and a standard time-of-flight system for the overall architecture. All the data gathered have been integrated and fused in a multiresolution model which can be visualized in real time at full accuracy with an innovative visualization system.

The results of a project aimed to the study, reconstruction and presentation to the public of a monument disassembled and dispersed, the mausoleum of the emperor Arrigo VII, are presented here. We used modern 3D graphics for the acquisition of accurate digital models of all the elements of the funerary complex, to draw hypothesis on its original architecture, and finally to present all this knowledge to the museum public. Issues emerged during 3D scanning are discussed. The multimedia museum presentation was implemented with an interactive visualization system, which was extended to manage standard multimedia data together with 3D geometry.

The program of scienti?c investigations planned in the framework of the restoration of Michelangelo's David produced several useful guidelines for de?ning and developing innovative ways to process and visualize 3D data in cultural heritage applications. Our ultimate goal was to include 3D graphics among the tools which can help restorers select the proper restoration procedures for the task at hand and objectively assess restoration results. For this, the David restoration was an ideal test bed to demonstrate the usefulness of digital 3D models and visualization tools in a restoration project. The scientific analysis program began in Florence, Italy, in 2002, under the direction of Mauro Matteini and Franca Falletti. Because a complex set of scientific investigations was planned before and after the restoration intervention, we could try various methodologies to support restorers and scientists with visualization tools based on 3D digital models. In particular, a 3D digital model can support restoration either as a tool for undertaking speci?c investigations or as a supporting media for archiving and integrating the restoration-related information, gathered with the different studies and analyses performed on the artwork.

Range map registration is still the most time consuming phase in 3D scanning. This is because real scanning set are composed of hundreds of range maps and their registration is still partially manual. We propose a new method which allows to manage complex scan sets acquired by following a regular scanner pose pattern. The method makes proficient use of some initial considerations and auxiliary data structures, which allow to simplify the range map registration problem. It is designed as an iterative solution, where pairs of correspondent vertices are selected through the computation of a regular n * n kernel which takes into account vertex normals and is defined in the 2D space of the range map (represented in implicit 2D format rather than as a triangle mesh in 3D space). The shape-characterization kernel and the metrics defined give a sufficiently accurate shape matching, which has been proven to fit well the requirements of automatic registration. The solution proposed has been tested on a number of complex scanning set and results are impressively better than previous solutions.

Post-processing of 3D scanned data is still the bottleneck for a wider diffusion of this technology. In this paper we describe our second generation tools for processing 3D scanned data. In particular, our tools support: range maps alignment, range maps merge (or fusion), mesh simplification and color attribute management. This software package has been implemented by scratch and encompasses both up-to-date solutions and some original methods (merging, simplification, color management and, in part, alignment). The paper presents the architecture of the tools, the features supported and algorithms used; finally, an evaluation of its use in the framework of a complex acquisition in the Cultural Heritage domain (3D scanning of a bronze statue) is reported.

Le moderne tecnologie di scansione digitale tridimensionale permettono di ricostruire, in maniera semi automatica, rappresentazioni digitali di oggetti reali caratterizzate da un alto grado di accuratezza e di ricchezza di dettaglio. Un accurato modello digitale del David di Michelangelo e' stato creato nell'ambito del progetto Digital Michelangelo. La disponibilità della rappresentazione digitale apre ampie possibilita' di utilizzo da parte degli addetti ai lavori (restauratori, archivisti, studiosi) od anche di semplici visitatori (virtuali e non). L'integrazione tra grafica 3D e tool di supporto al restauro e' un campo di ricerca aperto ed il progetto di restauro del David ha fornito numerosi spunti per la definizione e lo sviluppo di soluzioni innovative. L'attivita' del nostro gruppo si e' indirizzata su problematiche proposte direttamente dell'equipe di restauro e qui brevemente descritte. Il modello digitale e' stato usato in due accezioni diverse ma complementari: come strumento con cui eseguire indagini specifiche, o come supporto per l'indicizzazione e l'integrazione dei risultati di altre campagne di indagine.

Based on the integration of image acquisition techniques and real-time systems, an innovative system for cutting raw hides has been developed at ISTI-CNR. The aim is to partly automate the cutting process, so that minimal human intervention is needed. The current procedure for cutting animal hide is completely manual. The hide is spread out on a bench and expert operators decide the best cutting lines on the basis of the location of specific features. The hide is then manually cut using ad hoc knives and the parts are removed from the bench. The work of cutting the hide is the most time consuming step, and requires three or four workers.

We present a new integrated tool, DERMA, which allows to measure and assess the time evolution of chronic wounds. A laser triangulation 3D scanner is used to acquire the wound geometry with high precision and to capture an RGB image aligned to the geometry. DERMA provides a single and uniform interface to: manage patient data, 3D scanning of the lesion region, and to perform different kinds of measurements and comparisons: geometric (on the 3D model) and colorimetric (on the image). All acquired data (3D geometries and images) as well as the measures calculated are stored in a database for monitoring the evolution of the skin lesion over time. The tool, developed in collaboration with dermatologists, is now under field evaluation in two dermatological clinics monitoring the evolution of wounds due to different types of skin diseases.

The David restoration project (started in Florence in 2002) has given several guidelines to the definition and development of innovative solutions to process and visualize 3D data in the framework of Cultural Heritage (CH) applications. Our main goal has been to demonstrate the usefulness of digital 3D models and of visualization tools in the framework of a restoration project.

The Visual Computing Group of IEI-CNR, Pisa, has developed a suite of software procedures for the processing of 3D scanning data. The software package can be used for the automatic acquisition of 3D Cultural Heritage and for the creation of realistic 3D digital models.

Il contributo presenta sinteticamente le potenzialità delle tecnologie di acquisizione automatica delle caratteristiche di forma e colore di oggetti tridimensionali (altrimenti dette 3D scanning). Si introducono quindi le specifiche e le funzionalità di alcuni strumenti sviluppati: uno scanner ottico a basso costo e discreta qualità, un insieme di moduli software che permettono di gestire in modo completo e integrato le varie fasi del processo di acquisizione. Tali strumenti sono stati progettati con un preciso orientamento alla loro applicazione nel settore della rappresentazione digitale di Beni Culturali tridimensionali.

Automatic 3D acquisition devices (often called 3D scanners) allow to build highly accurate models of real 3D objects in a cost- and time-effective manner. We have experimented this technology in a particular application context: the acquisition of Cultural Heritage artifacts. Specific needs of this domain are: medium-high accuracy, easy of use, affordable cost of the scanning device, self-registered acquisition of shape and color data, and finally operational safety for both the operator and the scanned artifacts. According to these requirements, we designed a low-cost 3D scanner based on structured light which adopts a new, versatile colored stripe pattern approach. We present the scanner architecture, the software technologies adopted, and the first results of its use in a project regarding the 3D acquisition of an archeological statue.

This paper presents the initial results of the "Minerva Project" obtained by means of two different 3D scanning techniques. The "Minerva Project intends to show how 3D tecniques can integrate standard diagnostic methods giving useful and powerful tools to the restorers. The main goal of the project is to build complete 3D digital models of the Minerva statue before, during and after restoration in order to monitor the various phases of the restoration process.

In this paper we describe a 3D scanning software suite which gives support to most of the processing phases of a complex 3D scanning project. In particular, our tools support: range maps alignment, range maps merge, mesh editing and mesh simplification. The software suite has been implemented by scratch and encompasses both up-to-date solutions (alignment, editing) and some original methods (merging, simplification, and, in part, alignment). The architecture of the software suite is described and an evaluation of its use in the framework of a complex acquisition in the Cultural Heritage domain (3D scanning of a bronze statue) is reported

The paper presents a simple and eficient algorithm for the removal of small topological inconsistencies and high frequency details from surface models. The method, called Marching Intersections (MI), adopts a volumetric approach and acts as a resampling filter: all the intersection points between the input model and the lines of a user selected 30 reference grid are located and then, beginning from these intersections, an output surface is reconstructed. MI, which presents good characteristics in terms of eficiency, com- pactness, and quality of the output models, can be also used: for the conversion between different representation schemes; to pe~orm logical operations on geometric mod- els; for the topological simplijcation of surfaces; and for the simplification of huge meshes, i.e. meshes too large to be allocated in main memory during the simplijcation pro- cess. All these aspects are discussed in the paper and timing and graphic results are presented.

The recent evolution of graphics technology has been impressive, and the management of very complex models is now possible on inexpensive platforms. Moreover, automatic scanning devices (often called 3D scanners) allow to build highly accurate models of real 3D objects in a cost- and time-effective manner. This paper discusses some issues in the use of this technology by taking into account a particular application context: the acquisition of Cultural Heritage artifacts. Specific needs of this domain are: a high accuracy, a lower cost of the scanning devices and an improved usability of the data produced. We will present the results of two projects, aimed at: the design of a low-cost scanner based on structured light; the design of a data simplification tool which enables complex dataset visualization on low cost computers.

The paper presents a simple and efficient algorithm for the topological simplification of 3D meshes and/or boundary models. The algorithm, called Virtual Marching Cubes (VirtMC), belongs to the class of the simplification techniques based on a space decomposition approach, i.e. the approach based on input model discretization and surface reconstruction. With respect to other methods, VirtMC's discretization phase is more efficient and accurate and the underlying voxel model is not explicitly represented, leading to an impressive memory saving. VirtMC can also be used as a filter for other geometric manipulations, to regularize the data. For example, most geometric simplification codes expect a regular manifold mesh; VirtMC can be used to convert whichever geometric input in a regular manifold mesh, ready for simplification.