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Now showing 1 - 10 of 33
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    Interlocking Pieces for Printing Tangible Cultural Heritage Replicas
    (The Eurographics Association, 2014) Alemanno, Giuseppe; Cignoni, Paolo; Pietroni, Nico; Ponchio, Federico; Scopigno, Roberto; Reinhard Klein and Pedro Santos
    We propose a technique to decompose a 3D digital shape into a set of interlocking pieces that are easy to be manufactured and assembled. The pieces are designed so that they can be represented as a simple height field and, therefore, they can be manufactured by common 3D printers without the usage of supporting material. The removal of the supporting material is often a burdensome task and may eventually damage the surface of the printed object. Our approach makes the final reproduction cheaper, accurate and suitable for the reproduction of tangible cultural heritages. Moreover, since the proposed technique decomposes the artwork in pieces, it also overcomes the working space limits of common printers. The decomposition of the input (high-resolution) triangular mesh is driven by a coarse polygonal base mesh (representing the target subdivision in pieces); the height fields defining each piece are generated by sampling distances along the normal of each face composing the base mesh. A innovative interlocking mechanism allows adjacent pieces to plug each other to compose the final shape. This interlocking mechanism is designed to preserve the height field property of the pieces and to provide a sufficient degree of grip to ensure the assembled structure shape to be compact and stable. We demonstrate the effectiveness of our approach and show its limitations with some practical reproduction examples.
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    PileBars: Scalable Dynamic Thumbnail Bars
    (The Eurographics Association, 2012) Brivio, Paolo; Tarini, Marco; Ponchio, Federico; Cignoni, Paolo; Scopigno, Roberto; David Arnold and Jaime Kaminski and Franco Niccolucci and Andre Stork
    We introduce PileBars, a new class of animated thumbnail-bars supporting browsing of large image datasets (hundreds or thousands of images). Since the bar is meant to be just one element of a GUI, it covers only a small portion of the screen; yet it provides a global view of the entire dataset, without any scrolling panel. Instead, thumbnails are dynamically rearranged, resized and reclustered into adaptive layouts during the entire browsing process. The objective is to enable the user both to accurately pinpoint a specific image (even among semantically close ones), and to jump anywhere to ''distant'' parts of the dataset. The thumbnail layouts proposed maximize also the temporal coherence, thus allowing for smooth animations from one layout to the next. The system is very general: it can be driven by any application-specific image-to-image semantic distance function, and respects any user-defined total ordering of the images; the ordering can be either inferred from the semantic or be chosen independently from it, depending on the application. The applicability of the resulting system is tested in a number of practical applications and fits very well the issues in management of Cultural Heritage image collections.
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    Practical and Robust MLS-based Integration of Scanned Data
    (The Eurographics Association, 2008) Fiorin, Valentino; Cignoni, Paolo; Scopigno, Roberto; Vittorio Scarano and Rosario De Chiara and Ugo Erra
    The paper proposes a set of techniques for improving the quality of MLS surfaces reconstructed from point clouds that are composed by the union of many scanned range maps. The main idea of those techniques is that the range-map structure should be exploited during the reconstruction process and not lost in the uniform point soup that is usually fed into reconstruction algorithms; on this purpose a set of per-range-map weighting schemes are proposed. The presented weighting schemes allow to cope with some of the various issues that usually arise during the integration of point clouds composed by set of range maps, like tangible alignment errors, anisotropic error on sensor data and sensible difference in sampling quality.
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    Surface Light Field from Video Acquired in Uncontrolled Settings
    (The Eurographics Association, 2013) Palma, Gianpaolo; Desogus, Nicola; Cignoni, Paolo; Scopigno, Roberto; -
    This paper presents an algorithm for the estimation of the Surface Light Field using video sequences acquired moving the camera around the object. Unlike other state of the art methods, it does not require a uniform sampling density of the view directions, but it is able to build an approximation of the Surface Light Field starting from a biased video acquisition: dense along the camera path and completely missing in the other directions. The main idea is to separate the estimation of two components: the diffuse color, computed using statistical operations that allow the estimation of a rough approximation of the direction of the main light sources in the acquisition environment; the other residual Surface Light Field effects, modeled as linear combination of spherical functions. From qualitative and numerical evaluations, the final rendering results show a high fidelity and similarity with the input video frames, without ringing and banding effects.
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    Exploiting the scanning sequence for automatic registration of large sets of range maps
    (The Eurographics Association and Blackwell Publishing, Inc, 2005) Pingi, Paolo; Fasano, Andrea; Cignoni, Paolo; Montani, Claudio; Scopigno, Roberto
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    Generalized Trackball for Surfing Over Surfaces
    (The Eurographics Association, 2016) Malomo, Luigi; Cignoni, Paolo; Scopigno, Roberto; Giovanni Pintore and Filippo Stanco
    We present an efficient 3D interaction technique: generalizing the well known trackball approach, this technique unifies and blends the two common interaction mechanisms known as panning and orbiting. The approach allows to inspect a virtual object by navigating over its surrounding space, remaining at a chosen distance and performing an automatic panning over its surface. This generalized trackball allows an intuitive navigation of topologically complex shapes, enabling unexperienced users to visit hard-to-reach parts better and faster than with standard GUI components. The approach is based on the construction of multiple smooth approximations of the model under inspection; at rendering time, it constrains the camera to stay at a given distance to these approximations. The approach requires negligible preprocessing and memory overhead and works well for both mousebased and touch interfaces. An informal user study confirms the impact of the proposed technique.
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    Adaptively Adjusting Marching Cubes Output to Fit A Trilinear Reconstruction Filter
    (The Eurographics Association, 1998) Allamandri, Fabio; Cignoni, Paolo; Montani, Claudio; Scopigno, Roberto; Bartz, Dirk
    The paper focuses on the improvement of the quality of isosurfaces fitted on volume datasets with respect to standard MC solutions. The new solution presented improves the precision in the reconstruction process using an approach based on mesh re nement and driven by the evaluation of the trilinear reconstruction filter. The iso-surface reconstruction process is adaptive, to ensure that the complexity of the fitted mesh will not become excessive. The proposed approach has been tested on many datasets; we discuss the precision of the obtained meshs and report data on fitted meshes complexity and processing times.
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    Detection of Geometric Temporal Changes in Point Clouds
    (Copyright © 2016 The Eurographics Association and John Wiley & Sons Ltd., 2016) Palma, Gianpaolo; Cignoni, Paolo; Boubekeur, Tamy; Scopigno, Roberto; Chen, Min and Zhang, Hao (Richard)
    Detecting geometric changes between two 3D captures of the same location performed at different moments is a critical operation for all systems requiring a precise segmentation between change and no‐change regions. Such application scenarios include 3D surface reconstruction, environment monitoring, natural events management and forensic science. Unfortunately, typical 3D scanning setups cannot provide any one‐to‐one mapping between measured samples in static regions: in particular, both extrinsic and intrinsic sensor parameters may vary over time while sensor noise and outliers additionally corrupt the data. In this paper, we adopt a multi‐scale approach to robustly tackle these issues. Starting from two point clouds, we first remove outliers using a probabilistic operator. Then, we detect the actual change using the implicit surface defined by the point clouds under a Growing Least Square reconstruction that, compared to the classical proximity measure, offers a more robust change/no‐change characterization near the temporal intersection of the scans and in the areas exhibiting different sampling density and direction. The resulting classification is enhanced with a spatial reasoning step to solve critical geometric configurations that are common in man‐made environments. We validate our approach on a synthetic test case and on a collection of real data sets acquired using commodity hardware. Finally, we show how 3D reconstruction benefits from the resulting precise change/no‐change segmentation.Detecting geometric changes between two 3D captures of the same location performed at different moments is a critical operation for all systems requiring a precise segmentation between change and no‐change regions. Unfortunately, typical 3D scanning setups cannot provide any oneto‐one mapping between measured samples in static regions: both extrinsic and intrinsic sensor parameters may vary over time while sensor noise and outliers additionally corrupt the data. In this paper, we adopt a multi‐scale approach to robustly tackle these issues, obtaining a robust segmentation near the temporal intersection of the scans and in the areas with different sampling density and direction.
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    Color Enhancement for Rapid Prototyping
    (The Eurographics Association, 2008) Cignoni, Paolo; Gobbetti, Enrico; Pintus, Ruggero; Scopigno, Roberto; Michael Ashley and Sorin Hermon and Alberto Proenca and Karina Rodriguez-Echavarria
    We propose to exploit the color capabilities of recent rapid prototyping hardware devices to enhance the visual appearance of reproduced objects. In particular, by carefully pre-computing surface shading, we are able to counterbalance the sub-surface scattering (SSS) effects that hinder the perception of fine surface details. As a practical result, we are able to reproduce small scale copies of cultural heritage artifacts with an increased readability of the tiniest features and particulars, without requiring manual post-reproduction interventions or hand painting
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    A computer-assisted constraint-based system for assembling fragmented objects
    (The Eurographics Association, 2013) Palmas, Gregorio; Pietroni, Nico; Cignoni, Paolo; Scopigno, Roberto; -
    We propose a computer-assisted constraint-based methodology for virtual reassembly of Cultural Heritage (CH) artworks. Instead than focusing on automatic, unassisted reassembly, we targeted the scenarios where the reconstruction process is not be based on shape properties only but it is build over the experience and intuition of a CH expert. Our purpose is therefore to design a flexible interactive system, based on the selection of a set of constraints which relates different fragments, according to the understanding and experience of the CH operator. Once the user has defined those constraints, the system searches for a suitable solution, using a global energy minimization strategy that considers simultaneously all the pieces involved in the reconstruction process. Additionally, our framework provides the possibility to work in a hierarchical way, mimicking the traditional physical procedure that archaeologists use to reassemble tangible fractured objects. The frameworks is designed to work even with fragments that could have been severely damaged or eroded. On those datasets, automatic approaches may often fail, since the fractured regions do not contain enough geometric information to infer the correct matches. We present some successful uses of our framework on real application scenarios.