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Item 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 ErraThe 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.Item 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, RobertoItem Adaptively Adjusting Marching Cubes Output to Fit A Trilinear Reconstruction Filter(The Eurographics Association, 1998) Allamandri, Fabio; Cignoni, Paolo; Montani, Claudio; Scopigno, Roberto; Bartz, DirkThe 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.Item 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-EchavarriaWe 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 paintingItem A Multiresolution Model for Soft Objects Supporting Interactive Cuts and Lacerations(Blackwell Publishers Ltd and the Eurographics Association, 2000) Ganovelli, Fabio; Cignoni, Paolo; Montani, Claudio; Scopigno, RobertoPerforming a really interactive and physically-based simulation of complex soft objects is still an open problem in computer animation/simulation. Given the application domain of virtual surgery training, a complete model should be quite realistic, interactive and should enable the user to modify the topology of the objects. Recent papers propose the adoption of multiresolution techniques to optimize time performance by representing at high resolution only the object parts considered more important or critical. The speed up obtainable at simulation time are counterbalanced by the need of a preprocessing phase strongly dependent on the topology of the object, with the drawback that performing dynamic topology modification becomes a prohibitive issue. In this paper we present an approach that couples multiresolution and topological modifications, based on the adoption of a particle systems approach to the physical simulation. Our approach is based on a tetrahedral decomposition of the space, chosen both for its suitability to support a particle system and for the ready availability of many techniques recently proposed for the simplification and multiresolution management of 3D simplicial decompositions. The multiresolution simulation system is designed to ensure the required speedup and to support dynamic changes of the topology, e.g. due to cuts or lacerations of the represented tissue.Item Interactive Remote Exploration of Massive Cityscapes(The Eurographics Association, 2009) Benedetto, Marco Di; Cignoni, Paolo; Ganovelli, Fabio; Gobbetti, Enrico; Marton, Fabio; Scopigno, Roberto; Kurt Debattista and Cinzia Perlingieri and Denis Pitzalis and Sandro SpinaWe focus on developing a simple and efficient unified level-of-detail structure for networked urban model viewers. At the core of our approach is a revisitation of the BlockMap [CDG*07] data structure, originally introduced for encoding coarse representations of blocks of buildings to be used as direction-independent impostors when rendering far-away city blocks. The contribution of this paper is manifold: we extend the BlockMap representation to support sloped surfaces and input-sensitive sampling of color; we introduce a novel sampling strategy for building accurate BlockMaps; we show that BlockMaps can be used as a versatile and robust way to parameterize the visible surface of a highly complex model; we improve the expressiveness of urban models rendering by integrating an ambient occlusion term in the representation and describe an efficient method for computing it; we illustrate the design and implementation of a urban models streaming and visualization system and demonstrate its efficiency when browsing large city models in a limited bandwidth setting.Item 3D Enhanced Model from Multiple Data Sources for the Analysis of the Cylinder Seal of Ibni-Sharrum(The Eurographics Association, 2008) Pitzalis, Denis; Cignoni, Paolo; Menu, Michel; Aitken, Genevieve; Michael Ashley and Sorin Hermon and Alberto Proenca and Karina Rodriguez-EchavarriaIn this paper we present the result of the integration of multiple data sources of different 3D acquisition techniques. These acquisitions have been done in order to create a new way to document works of art that have been applied to the "Cylinder seal of Ibni-Sharrum". X-ray tomography has been used to reveal the exact position of inclusions and the presence fissure in the mineral structure; optical micro topography gives the prints of the surface of the seal with a unparallelled precision of up to 0.1μm. Finally a lower resolution 3D model obtained via photogrammetry has been used as a starting point where the tomographic and micro topographic data sets have been superimposed and integrated without precision loss. Furthermore, the textures obtained from HDR photographs has been registered and merged onto the high resolution mesh. These methods have pros and cons that will be discussed and the final obtained model will be the sum of all the complementary cons. The final result of this interdisciplinary investigation will help the curator to better describe the fabrication techniques used in order to achieve the final object and a contemporary artist to do a reproduction of the cylinder at a scale of 1000:1.Item Tutorial 2 - Level-of-Detail in Surface and Volume Modeling(Eurographics Association, 1999) De Floriani, Leila; Puppo, Enrico; Cignoni, Paolo; Scopigno, Roberto-Item Normal Enhancement for Interactive Non-photorealistic Rendering(Eurographics Association, 2002) Cignoni, Paolo; Scopigno, Roberto; Tarini, MarcoWe present a simple technique to improve the perception of shape of an object. Bump mapping is well-known in the computer graphics community for providing the impression of small-scale geometrical features (which actually are not there). Here, we propose a similar approach (variation of normals) for the purpose of enhancing perception of the given geometry. Our approach is based on a simple modification of the surface normals in order to enhance the geometric features of the object during the rendering. The enhanced normals produced by this approach can be used in any rendering technique. The technique presented is particularly well suited to improve the rendering of mechanical parts where common cheap shading techniques can often generate shading ambiguities.Item Stereo Light Probe(The Eurographics Association and Blackwell Publishing Ltd, 2008) Corsini, Massimiliano; Callieri, Marco; Cignoni, PaoloIn 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.