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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.
Computational Design of Fabricable Geometric Patterns
(The Eurographics Association, 2023) Scandurra, Elena; Laccone, Francesco; Malomo, Luigi; Callieri, Marco; Cignoni, Paolo; Giorgi, Daniela; Banterle, Francesco; Caggianese, Giuseppe; Capece, Nicola; Erra, Ugo; Lupinetti, Katia; Manfredi, Gilda
This paper addresses the design of surfaces as assemblies of geometric patterns with predictable performance in response to mechanical stimuli. We design a family of tileable and fabricable patterns represented as triangle meshes, which can be assembled for creating surface tessellations. First, a regular recursive subdivision of the planar space generates different geometric configurations for candidate patterns, having interesting and varied aesthetic properties. Then, a refinement step addresses manufacturability by solving for non-manifold configurations and sharp angles which would produce disconnected or fragile patterns. We simulate our patterns to evaluate their mechanical response when loaded in different scenarios targeting out-of-plane bending. Through a simple browsing interface, we show that our patterns span a variety of different bending behaviors. The result is a library of patterns with varied aesthetics and predefined mechanical behavior, to use for the direct design of mechanical metamaterials. To assess the feasibility of our approach, we show a pair of fabricated 3D objects with different curvatures.
Optimizing Object Decomposition to Reduce Visual Artifacts in 3D Printing
(The Eurographics Association and John Wiley & Sons Ltd., 2020) Filoscia, Irene; Alderighi, Thomas; Giorgi, Daniela; Malomo, Luigi; Callieri, Marco; Cignoni, Paolo; Panozzo, Daniele and Assarsson, Ulf
We propose a method for the automatic segmentation of 3D objects into parts which can be individually 3D printed and then reassembled by preserving the visual quality of the final object. Our technique focuses on minimizing the surface affected by supports, decomposing the object into multiple parts whose printing orientation is automatically chosen. The segmentation reduces the visual impact on the fabricated model producing non-planar cuts that adapt to the object shape. This is performed by solving an optimization problem that balances the effects of supports and cuts, while trying to place both in occluded regions of the object surface. To assess the practical impact of the solution, we show a number of segmented, 3D printed and reassembled objects.
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.
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.
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.
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.
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 Santos
Digital 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.
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.
Another Brick in the Wall: Improving the Assisted Semantic Segmentation of Masonry Walls
(The Eurographics Association, 2020) Pavoni, Gaia; Giuliani, Francesca; Falco, Anna De; Corsini, Massimiliano; Ponchio, Federico; Callieri, Marco; Cignoni, Paolo; Spagnuolo, Michela and Melero, Francisco Javier
In Architectural Heritage, the masonry's interpretation is an essential instrument for analyzing the construction phases, the assessment of structural properties, and the monitoring of its state of conservation. This work is generally carried out by specialists that, based on visual observation and their knowledge, manually annotate ortho-images of the masonry generated by photogrammetric surveys. This results in vectorial thematic maps segmented according to their construction technique (isolating areas of homogeneous materials/structure/texture) or state of conservation, including degradation areas and damaged parts. This time-consuming manual work, often done with tools that have not been designed for this purpose, represents a bottleneck in the documentation and management workflow and is a severely limiting factor in monitoring large-scale monuments (e.g.city walls). This paper explores the potential of AI-based solutions to improve the efficiency of masonry annotation in Architectural Heritage. This experimentation aims at providing interactive tools that support and empower the current workflow, benefiting from specialists' expertise.

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