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Item 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-SalamaWe 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.Item 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.Item 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 GutierrezWe 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.Item 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 BrunetIn 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.Item 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. ScopignoWe 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.Item Digital Fabrication Technologies for Cultural Heritage (STAR)(The Eurographics Association, 2014) Scopigno, Roberto; Cignoni, Paolo; Pietroni, Nico; Callieri, Marco; Dellepiane, Matteo; Reinhard Klein and Pedro SantosDigital Fabrication technologies exploit a variety of basic technologies to create tangible reproductions of 3D digital models. Even though current 3D printing pipelines still suffer of several restrictions, the reproduction accuracy has gradually reached an excellent level. Thanks to this advancement, the interests of manufacturing industry with respect to 3D printing techniques has significantly grown during the last decade. However, digital fabrication techniques have been demonstrated to be effective also in other contexts, such as medical applications and Cultural Heritage (CH). The goal of this survey paper is to introduce briefly the different fabrication technologies, to discuss some successful utilization of 3D printing in the CH domain and, finally, to review the work done so far to extend fabrication technology capabilities to cope with the specific issues that characterize the usage of digital fabrication in the CH domain.Item The Dream and the Cross: a 3D-referenced, web-based digital edition(The Eurographics Association, 2013) Leoni, Chiara; Callieri, Marco; Dellepiane, Matteo; Turco, Roberto Rosselli Del; O'Donnel, Daniel; Scopigno, Roberto; -The Dream of the Rood is one of the earliest Christian poems in the corpus of Old English literature, and an example of the genre of dream poetry. While its complete text can be found in the 10th Century ''Vercelli Book'', the poem is considerably older, and its oldest occurrence is carved (in runes) on the 7 8th Century Ruthwell Stone Cross. In this paper, we present the prototype of a web-based digital edition of the Dream of the Rood, as it appears on the Ruthwell Cross. The multimedia framework presents the highly detailed 3D model acquired with 3D Scanning technology, together with the transcription and translation of the runes that can be found on its surface. The textual and spatial information are linked through a system of bi-directional links called spots, that give the possibility to the user to have a free navigation over the multimedia content, keeping the 3D and textual data synchronized. The proposed work provides discussion and solution on two main issues related to digital editions: the integration of three dimensional content in the context of the presentation on the web platform of heterogeneous multimedia data, and the creation of an XML encoding that could account for the necessities of 3D data disposition, but keeping the encoding rules in the context of the standards of the community.Item Automatic Selection of Video Frames for Path Regularization and 3D Reconstruction(The Eurographics Association, 2016) Pavoni, Gaia; Dellepiane, Matteo; Callieri, Marco; Scopigno, Roberto; Chiara Eva Catalano and Livio De LucaVideo sequences can be a valuable source to document the state of objects and sites. They are easy to acquire and they usually ensure a complete coverage of the object of interest. One of their possible uses is to recover the acquisition path, or the 3D shape of the scene. This can be done by applying structurefrom- motion techniques to a representative set of frames extracted from the video. This paper presents an automatic method for the extraction of a predefined number of representative frames that ensures an accurate reconstruction of the sequence path, and possibly enhances the 3D reconstruction of the scene. The automatic extraction is obtained by analyzing adjacent frames in a starting subset, and adding/removing frames so that the distance between them remains constant. This ensures the reconstruction of a regularized path and an optimized coverage of all the scene. Finally, more frames are added in the portions of the sequence when more detailed objects are framed. This ensures a better description of the sequence, and a more accurate dense reconstruction. The method is automatic, fast and independent from any assumption about the acquired object or the acquisition strategy. It was tested on a variety of different video sequences, showing that a satisfying result can be obtained regardless of the length and quality of the input.Item Developing and Maintaining a Web 3D Viewer for the CH Community: an Evaluation of the 3DHOP Framework(The Eurographics Association, 2018) Potenziani, Marco; Callieri, Marco; Scopigno, Roberto; Sablatnig, Robert and Wimmer, Michael3DHOP (3D Heritage On-line Presenter) has been released 4 years ago, as an open-source framework for the creation of interactive visualization of 3D content on the web, aimed at the CH field. Transforming a research tool into a software ''product'' usable by the heterogeneous CH community is not a simple task and requires a significant amount of resources plus a specific design. This work presents the evolution of the 3DHOP system, and the complex relationship with its community of users, made of content creators, CH experts and general public. We will discuss the new features introduced, as well as the design and implementation strategy employed to maintain the software and make it usable by developers. We will evaluate the effectiveness of the platform by illustrating some of the applications built with 3DHOP either internally or by external users, as well as by presenting the results of a survey aimed at gathering the opinions and suggestions of the user community.Item EnvyDepth: An Interface for Recovering Local Natural Illumination from Environment Maps(The Eurographics Association and Blackwell Publishing Ltd., 2013) Banterle, Francesco; Callieri, Marco; Dellepiane, Matteo; Corsini, Massimiliano; Pellacini, Fabio; Scopigno, Roberto; B. Levy, X. Tong, and K. YinIn this paper, we present EnvyDepth, an interface for recovering local illumination from a single HDR environment map. In EnvyDepth, the user quickly indicates strokes to mark regions of the environment map that should be grouped together in a single geometric primitive. From these annotated strokes, EnvyDepth uses edit propagation to create a detailed collection of virtual point lights that reproduce both the local and the distant lighting effects in the original scene. When compared to the sole use of the distant illumination, the added spatial information better reproduces a variety of local effects such as shadows, highlights and caustics. Without the effort needed to create precise scene reconstructions, EnvyDepth annotations take only tens of seconds to produce a plausible lighting without visible artifacts. This is easy to obtain even in the case of complex scenes, both indoors and outdoors. The generated lighting environments work well in a production pipeline since they are efficient to use and able to produce accurate renderings.