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Mapping highly detailed color information on extremely dense 3D models: the case of David s restoration
(The Eurographics Association, 2007) Dellepiane, Matteo; Callieri, Marco; Ponchio, Federico; Scopigno, Roberto; David B. Arnold and Andrej Ferko
The support of advanced Information Technology (IT) to preservation, restoration and documentation of Cultural Heritage is becoming a very important goal for the research community. Michelangelo's David was one of the first applications of 3D scanning technology on a highly popular work of art. The subsequent restoration campaign, started in 2002 and concluded in 2004, was also a milestone for the adoption of modern scientific analysis procedures and IT tools in the framework of a restoration process. One of the focuses in this restoration was also methodological, i.e. to plan and adopt innovative ways to document the restoration process. In this paper we present the results of an integration of different restoration data (2D and 3D datasets) which has been concluded recently. The recent evolution of HW and SW graphics technologies gave us the possibility to interactively visualize an extremely dense 3D model which incorporates the color information provided by two professional photographic campaigns, made before and after the restoration. Moreover, we present the results concerning the mapping, in this case on the 2D media, of the reliefs produced by restorers to assess and document the status of the marble surface before the restoration took place. This result could lead to new and fascinating applications of computer graphics for preservation, restoration and documentation of Cultural Heritage.
Multiple Uses of 3D Scanning for the Valorization of an Artistic Site: the Case of Luni
(The Eurographics Association, 2008) Dellepiane, Matteo; Callieri, Marco; Paribeni, Emanuela; Sorge, Elena; Sulfaro, Nino; Marianelli, Veronica; Scopigno, Roberto; Vittorio Scarano and Rosario De Chiara and Ugo Erra
The heritage site of Luni is a very interesting location, which tells the story of an ancient roman colony, and of an area where different cultures left their heritage. In particular, the remains of the pediments of an ancient temple represent a very interesting case and an open field of study for art historians. The scanning of a group of statue belonging to the pediments showed that the produced 3D models could be used in several ways, not only for archival and presentation purposes but also to provide interactive support for the work of the restorers and the scholars. In particular, the use of 3D models to propose and validate hypothesis about the original position of the fragments in the context of the fronton could be an alternative solution to the direct manipulation of them. Moreover, the analysis of the original color of the statues, and the representation different hypothesis about the ancient appearance can be produced through the interactive editing of the 3D models of the statues. In this paper we present the scanning campaign which resulted in the acquisition of five statues,the preliminary results of some of the uses of the models produced with acquired data, and a brief description of other possible future applications of them. This shows how 3D scanning can be considered by now a mature technology for the support of restoration and preservation of Cultural Heritage.
High Quality PTM Acquisition: Reflection Transformation Imaging for Large Objects
(The Eurographics Association, 2006) Dellepiane, Matteo; Corsini, Massimiliano; Callieri, Marco; Scopigno, Roberto; Marinos Ioannides and David Arnold and Franco Niccolucci and Katerina Mania
Reflection Transformation Imaging has proved to be a powerful method to acquire and represent the 3D reflectance properties of an object, displaying them as a 2D image. Recently, Polynomial Texture Maps (PTM), which are relightable images created from a set of photos of the object taken under several different lighting conditions, have been used in Cultural Heritage field to document and virtually inspect several sets of small objects, such as cuneiform tablets and coins. In this paper we explore the possibility of producing high quality PTM of medium or large size objects. The aim is to analyze the acquisition pipeline, resolving all the issues related to the size of the object, and the conditions of acquisition. We will discuss issues regarding acquisition planning and data gathering. We also present a new tool to interactively browse high resolution PTMs. Moreover, we perform some quality assessment considerations, in order to study the degradation of quality of the PTMs respect to the number and position of lights used to acquire the PTM. The results of our acquisition system are presented with some examples of PTMs of large artifacts like a sarcophagus of 2.4 × 1 m size. PTM can be a good alternative to 3D scanning for capturing and representing certain class of objects, like bas-relieves, having lower costs in terms of acquisition equipment and data processing time.
Pushing Time-of-Flight Scanners to the Limit
(The Eurographics Association, 2009) Callieri, Marco; Cignoni, Paolo; Dellepiane, Matteo; Scopigno, Roberto; Kurt Debattista and Cinzia Perlingieri and Denis Pitzalis and Sandro Spina
The paper describes a pipeline for 3D scanning acquisition and processing that allow to exploit the utmost precision and quality out of ToF scanners. The proposed approach capitalize on the knowledge of the distribution of the noise to apply sophisticated fairing techniques for cleaning up the data. Leveraging on the very dense sampling of this kind of scanners we show that is possible to attain high accuracy. We present a practical application of the proposed approach for the scanning of a large (5mt) statue with millimetric precision.
Instant Sound Scattering
(The Eurographics Association, 2007) Tsingos, Nicolas; Dachsbacher, Carsten; Lefebvre, Sylvain; Dellepiane, Matteo; Jan Kautz and Sumanta Pattanaik
Real-time sound rendering engines often render occlusion and early sound reflection effects using geometrical techniques such as ray or beam tracing. They can only achieve interactive rendering for environments of low local complexity resulting in crude effects which can degrade the sense of immersion. However, surface detail or complex dynamic geometry has a strong influence on sound propagation and the resulting auditory perception. This paper focuses on high-quality modeling of first-order sound scattering. Based on a surface-integral formulation and the Kirchhoff approximation, we propose an efficient evaluation of scattering effects, including both diffraction and reflection, that leverages programmable graphics hardware for dense sampling of complex surfaces. We evaluate possible surface simplification techniques and show that combined normal and displacement maps can be successfully used for audio scattering calculations. We present an auralization framework that can render scattering effects interactively thus providing a more compelling experience. We demonstrate that, while only considering first order phenomena, our approach can provide realistic results for a number of practical interactive applications. It can also process highly detailed models containing millions of unorganized triangles in minutes, generating high-quality scattering filters. Resulting simulations compare well with on-site recordings showing that the Kirchhoff approximation can be used for complex scattering problems.
Using 3D Scanning to Analyze a Proposal for the Attribution of a Bronze Horse to Leonardo da Vinci
(The Eurographics Association, 2007) Dellepiane, Matteo; Callieri, Marco; Fondersmith, Mark; Cignoni, Paolo; Scopigno, Roberto; D. Arnold and F. Niccolucci and A. Chalmers
In this paper we present how technologies developed in the context of 3D graphics (3D scanning and image-to- 3D-model mapping) have been used to evaluate in a metrically objective way the plausibility of an attribution hypothesis of a Renaissance artifact. The artifact considered is a small bronze horse (Archeological Museum, Florence, Italy), which was discovered to be very similar to a silverpoint drawing by Leonardo (Leonardo drawing #358, Windsor Royal Library, UK), thus originating an attribution hypothesis. A highly accurate digital replica of this small bronze statue was reconstructed by means of triangulation-based 3D scanning technology. Using image-to-3D-model mapping techniques the Leonardo s drawing depicting a very similar horse has been aligned to the digital 3D model, reconstructing in a virtual manner the ideal vantage points which could have been used to sketch the drawings of the horse (in the hypothesis that Leonardo had drawn it by directly looking at the bronze). The same approach has been also tried with other Leonardo s drawings depicting a similar subject, but none of those was sufficiently compatible in shape with the bronze horse to allow convergence of the image-to-3D mapping process. The approach proposed allows us to give some visually objective evidences about the shape similarity issue, which was the origin of this attribution attempt. At the same time, a purely technical evaluation does not close the attribution issue. Further archival research and expertise will be needed to solve and assess the issue of this disputed hypothesis.
Image-to-Geometry Registration: a Mutual Information Method exploiting Illumination-related Geometric Properties
(The Eurographics Association and Blackwell Publishing Ltd, 2009) Corsini, Massimiliano; Dellepiane, Matteo; Ponchio, Federico; Scopigno, Roberto
This work concerns a novel study in the field of image-to-geometry registration. Our approach takes inspiration from medical imaging, in particular from multi-modal image registration. Most of the algorithms developed in this domain, where the images to register come from different sensors (CT, X-ray, PET), are based on Mutual Information, a statistical measure of non-linear correlation between two data sources. The main idea is to use mutual information as a similarity measure between the image to be registered and renderings of the model geometry, in order to drive the registration in an iterative optimization framework. We demonstrate that some illumination-related geometric properties, such as surface normals, ambient occlusion and reflection directions can be used for this purpose. After a comprehensive analysis of such properties we propose a way to combine these sources of information in order to improve the performance of our automatic registration algorithm. The proposed approach can robustly cover a wide range of real cases and can be easily extended.
MeshLab: an Open-Source Mesh Processing Tool
(The Eurographics Association, 2008) Cignoni, Paolo; Callieri, Marco; Corsini, Massimiliano; Dellepiane, Matteo; Ganovelli, Fabio; Ranzuglia, Guido; Vittorio Scarano and Rosario De Chiara and Ugo Erra
The paper presents MeshLab, an open source, extensible, mesh processing system that has been developed at the Visual Computing Lab of the ISTI-CNR with the helps of tens of students. We will describe the MeshLab architecture, its main features and design objectives discussing what strategies have been used to support its development. Various examples of the practical uses of MeshLab in research and professional frameworks are reported to show the various capabilities of the presented system.
Artifacts Removal for Color Projection on 3D Models using Flash Light
(The Eurographics Association, 2009) Dellepiane, Matteo; Callieri, Marco; Corsini, Massimiliano; Cignoni, Paolo; Scopigno, Roberto; Kurt Debattista and Cinzia Perlingieri and Denis Pitzalis and Sandro Spina
Abstract Lighting artifacts are one of the main issues in digital photography: complex light setups are needed to attenuate or remove them. Flash light is a very easy way to illuminate an object or an environment, but it is rarely considered in most of the Computer Graphics and Computer Vision applications. This is due to the big amount of artifacts introduced by this lighting, and to the difficulty in modeling its behavior. In this paper we present a simple method to use flash light in the context of color acquisition and mapping on 3D models. We propose a simple way to accurately estimate the flash position with respect to the camera, and we propose two automatic methods to detect and remove artifacts from a set of images which are registered to a 3D model. These methods are integrated in the context of a color mapping framework. The results show that it is possible to obtain high quality colored 3D models using flash light, which is the most simple illumination setup. This results are extremely important especially in the context of Cultural heritage, where the acquisition of color has often to be performed on site, without a specific lighting setup.
Uses of uncalibrated images to enrich3D models information
(Dellepiane, 2009) Dellepiane, Matteo;
La diminuzione dei costi delle fotocamere digitali semi-professionali ha portato allapossibilit per tutti di acquisire immagini ad alta definizione in modo molto semplice.Tuttavia, l interpretazione di queste immagini, nell ambito di tecniche di analisi dellascena di ricostruzione 3D della stessa, risulta ancora molto difficile a causa dellaricchezza di informazione acquisita. Nel caso in cui si conosca per una rappresentazione,anche semplificata, della scena, possibile estrarre dati interessanti in manieraautomatica o semi-automatica.Questi dati possono essere utilizzati in diversi modi per arricchire la qualit dei dati3D in possesso. Nell ambito di questa tesi, sono quindi presentate alcune tecnicheper l uso di immagini non registrate per l arricchimento di modelli 3D.In particolare, due possibili campi di applicazione sono considerati: l acquisizione,proiezione e visualizzazione dell informazione di colore e la modifica della geometriadi partenza.Per quanto riguarda la gestione del colore, sono presentate alcune soluzione praticheed efficaci, che hanno portato a importanti risultati nell ambito di svariati progettinell ambito in particolare dei Beni Culturali.Considerando invece le tecniche di modifica della geometria, sono presentati dueapprocci che apportano cambiamenti nella topologia di modelli 3D gi esistenti. Inparticolare, nella prima tecnica le informazioni estratte dalle immagini sono usateper produrre modelli tridimesionali di teste umane, usati per simulazioni di soundscattering nell ambito di applicazioni di 3D sound rendering. Il secondo metodo permetteinvece di completare modelli 3D con buchi, utilizzando immagini dell oggettoreale su cui sia stato proiettato un pattern laser predefinito.Infine, sono presentate alcune interessanti indicazioni a proposito di possibili sviluppifuturi dei metodi proposti, per delineare la direzione di questo promettente argomentodi ricerca. - The decrease in costs of semi-professional digital cameras has led to the possibilityfor everyone to acquire a very detailed description of a scene in a very short time.Unfortunately, the interpretation of the images is usually quite hard, due to the amountof data and the lack of robust and generic image analysis methods. Nevertheless, if ageometric description of the depicted scene is available, it gets much easier to extractinformation from 2D data.This information can be used to enrich the quality of the 3D data in several ways.In this thesis, several uses of sets of unregistered images for the enrichment of 3Dmodels are shown.In particular, two possible fields of application are presented: the color acquisition,projection and visualization and the geometry modification.Regarding color management, several practical and cheap solutions to overcome themain issues in this field are presented. Moreover, some real applications, mainly relatedto Cultural Heritage, show that provided methods are robust and effective.In the context of geometry modification, two approaches are presented to modify alreadyexisting 3D models. In the first one, information extracted from images is usedto deform a dummy model to obtain accurate 3D head models, used for simulationin the context of three-dimensional audio rendering. The second approach presentsa method to fill holes in 3D models, with the use of registered images depicting apattern projected on the real object.Finally, some useful indications about the possible future work in all the presentedfields are given, in order to delineate the developments of this promising direction ofresearch.

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