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Geometry-aware Video Registration
(The Eurographics Association, 2010) Palma, Gianpalo; Callieri, Marco; Dellepiane, Matteo; Corsini, Massimiliano; Scopigno, Roberto; Reinhard Koch and Andreas Kolb and Christof Rezk-Salama
We present a new method for the accurate registration of video sequences of a real object over its dense triangular mesh. The goal is to obtain an accurate video-to-geometry registration to allow the bidirectional data transfer between the 3D model and the video using the perspective projection defined by the camera model. Our solution uses two different approaches: feature-based registration by KLT video tracking, and statistic-based registration by maximizing the Mutual Information (MI) between the gradient of the frame and the gradient of the rendering of the 3D model with some illumination related properties, such as surface normals and ambient occlusion. While the first approach allows a fast registration of short sequences with simple camera movements, the MI is used to correct the drift problem that KLT tracker produces over long sequences, due to the incremental tracking and the camera motion. We demonstrate, using synthetic sequences, that the alignment error obtained with our method is smaller than the one introduced by KLT, and we show the results of some interesting and challenging real sequences of objects of different sizes, acquired under different conditions.
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.
Digital reconstruction and visualization in archaeology. Case-study drawn from the work of the Swedish Pompeii Project
(The Eurographics Association, 2013) Dell'Unto, Nicolò; Ferdani, Daniele; Leander, Anne Marie; Dellepiane, Matteo; Callieri, Marco; Lindgren, Stefan; -
The Swedish Pompeii Project started in 2000 as a research and fieldwork activity initiated by the Swedish Institute in Rome. The aim was to record and analyze an entire Pompeian city-block, Insula V 1. Since autumn 2011 a new branch of advanced digital archaeology, involving 3D reconstructions and documentation methods, was added to the project agenda. The insula was completely digitized using laser scanner technology and the raw data were employed to develop different research activities in the area of digital visualization. This paper presents the recent results of the 3D interpretation of the house of Caecilius Iucundus. This research activity was developed employing a large variety of historical and archaeological sources such as: archaeological reports, historical image documentation (printed as well as in edited material) and analysis of the in situ structures. This work was characterized by the experimentation of a new workflow of data development, where the elaboration of the interpreted structures took place directly in virtual space, using the scanned model as geometrical reference. This method easily connected all the historical and archaeological sources collected for the interpretation, opening a new discussion about different possible interpretation of the house. Moreover, a Cave Automatic Virtual Environment (CAVE) was used in different occasions as platform where the different hypotheses could be discussed in the context given by the actual state of the archaeological structures. The use of an accurate and resolute replica of the site as a backdrop for the virtual reconstruction allowed a high level of control on the proposed hypotheses during the interpretation process. This study enabled the acquisition of new and important information about the house, thus, bringing a significant contribution to the archaeological analysis of Insula V 1, suggested as pilot project for wider use.
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.
A Statistical Method for SVBRDF Approximation from Video Sequences in General Lighting Conditions
(The Eurographics Association and Blackwell Publishing Ltd., 2012) Palma, Gianpaolo; Callieri, Marco; Dellepiane, Matteo; Scopigno, Roberto; Fredo Durand and Diego Gutierrez
We present a statistical method for the estimation of the Spatially Varying Bidirectional Reflectance Distribution Function (SVBRDF) of an object with complex geometry, starting from video sequences acquired with fixed but general lighting conditions. The aim of this work is to define a method that simplifies the acquisition phase of the object surface appearance and allows to reconstruct an approximated SVBRDF. The final output is suitable to be used with a 3D model of the object to obtain accurate and photo-realistic renderings. The method is composed by three steps: the approximation of the environment map of the acquisition scene, using the same object as a probe; the estimation of the diffuse color of the object; the estimation of the specular components of the main materials of the object, by using a Phong model. All the steps are based on statistical analysis of the color samples projected by the video sequences on the surface of the object. Although the method presents some limitations, the trade-off between the easiness of acquisition and the obtained results makes it useful for practical applications.
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.
Alchemy in 3D - A Digitization for a Journey Through Matter
(IEEE, 2015) Callieri, Marco; Pingi, Paolo; Potenziani, Marco; Dellepiane, Matteo; Pavoni, Gaia; Lureau, Aurelia; Scopigno, Roberto; Gabriele Guidi and Roberto Scopigno and Pere Brunet
In this work, we will present the outcomes of the 3D diagnostic investigations carried out on the painting Alchemy by Jackson Pollock. Thanks to an accurate digitization and a careful processing, we were able to generate a very precise high-resolution 3D model that proved to be useful in different stages of the diagnostic and conservation campaign. The 3D model was integrated in the conservation process, along with the other diagnostic investigations; the geometric data was also used to produce images and video sequences for dissemination purposes. The most interesting aspect of the work, however, was the idea of going beyond photo-realism and the use of the scanner-measured geometry to try to interpret and understand the traces and signs on the surface of the painting, in relation with the gestures and techniques used by Pollock while painting this masterpiece. Combining the knowledge of the curators and the metric data gathered in the digitization, we were able to discover and validate several interesting aspects of the painting, in the direction of trying to better understanding the painting process which was, in the idea of the artist, an essential part of the artwork. The 3D model of the artwork played a central role also in the temporary exhibition created for the dissemination of the conservation and the diagnostic campaign to the museum visitors. This was also done following the idea of using the geometry to explain the gestures, actions and techniques of Jackson Pollock at work. The 3D model was used to create an interactive kiosk, to have the visitors navigate the model and access explanations of relevant geometrical details and to produce a 1:1 physical reproduction to give the public the possibility to physically interact with the artwork.
Stereo Light Probe
(The Eurographics Association and Blackwell Publishing Ltd, 2008) Corsini, Massimiliano; Callieri, Marco; Cignoni, Paolo
In this paper we present a practical, simple and robust method to acquire the spatially-varying illumination of a real-world scene. The basic idea of the proposed method is to acquire the radiance distribution of the scene using high-dynamic range images of two reflective balls. The use of two light probes instead of a single one allows to estimate, not only the direction and intensity of the light sources, but also the actual position in space of the light sources. To robustly achieve this goal we first rectify the two input spherical images, then, using a region-based stereo matching algorithm, we establish correspondences and compute the position of each light. The radiance distribution so obtained can be used for augmented reality applications, photo-realistic rendering and accurate reflectance properties estimation. The accuracy and the effectiveness of the method have been tested by measuring the computed light position and rendering synthetic version of a real object in the same scene. The comparison with standard method that uses a simple spherical lighting environment is also shown.
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.
A Streaming Framework for Seamless Detailed Photo Blending on Massive Point Clouds
(The Eurographics Association, 2011) Pintus, Ruggero; Gobbetti, Enrico; Callieri, Marco; A. Day and R. Mantiuk and E. Reinhard and R. Scopigno
We present an efficient scalable streaming technique for mapping highly detailed color information on extremely dense point clouds. Our method does not require meshing or extensive processing of the input model, works on a coarsely spatially-reordered point stream and can adaptively refine point cloud geometry on the basis of image content. Seamless multi-band image blending is obtained by using GPU accelerated screen-space operators, which solve point set visibility, compute a per-pixel view-dependent weight and ensure a smooth weighting function over each input image. The proposed approach works independently on each image in a memory coherent manner, and can be easily extended to include further image quality estimators. The effectiveness of the method is demonstrated on a series of massive real-world point datasets.

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