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Item Generalized Trackball for Surfing Over Surfaces(The Eurographics Association, 2016) Malomo, Luigi; Cignoni, Paolo; Scopigno, Roberto; Giovanni Pintore and Filippo StancoWe 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.Item 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.Item Harvesting Dynamic 3D Worlds from Commodity Sensor Clouds(The Eurographics Association, 2016) Boubekeur, Tamy; Cignoni, Paolo; Eisemann, Elmar; Goesele, Michael; Klein, Reinhard; Roth, Stefan; Weinmann, Michael; Wimmer, Michael; Chiara Eva Catalano and Livio De LucaThe EU FP7 FET-Open project ''Harvest4D: Harvesting Dynamic 3D Worlds from Commodity Sensor Clouds'' deals with the acquisition, processing, and display of dynamic 3D data. Technological progress is offering us a wide-spread availability of sensing devices that deliver different data streams, which can be easily deployed in the real world and produce streams of sampled data with increased density and easier iteration of the sampling process. These data need to be processed and displayed in a new way. The Harvest4D project proposes a radical change in acquisition and processing technology: instead of a goaldriven acquisition that determines the devices and sensors, its methods let the sensors and resulting available data determine the acquisition process. A variety of challenging problems need to be solved: huge data amounts, different modalities, varying scales, dynamic, noisy and colorful data. This short contribution presents a selection of the many scientific results produced by Harvest4D. We will focus on those results that could bring a major impact to the Cultural Heritage domain, namely facilitating the acquisition of the sampled data or providing advanced visual analysis capabilities.Item Anisotropic MatCap: Easy Capture and Reproduction of Anisotropic Materials(The Eurographics Association, 2016) Magri, Dario; Cignoni, Paolo; Tarini, Marco; Giovanni Pintore and Filippo StancoWe propose Anisotropic MatCap, a simple data structure based on a small volumetric texture that is able to represent, under a fixed lighting, the behavior of anisotropic materials. The data structure is designed to allow fast and practical capture of real-world anisotropic materials (like for example fabrics) and to be used in real-time renderings, requiring only negligible time and texture memory overheads. The resulting technique is suited for application scenarios where digital objects must be inspected by an end user, recreating the look of an object made of a captured anisotropic material and seen under the predetermined lighting conditions. The technique proved particularly useful for garments and cloth visualization and design.Item State of The Art on Functional Fabrication(The Eurographics Association, 2016) Sá, Asla Medeiros e; Echavarria, Karina Rodriguez; Pietroni, Nico; Cignoni, Paolo; A. Medeiros e Sa and N. Pietroni and K. Rodriguez EchavarriaDigital fabrication technologies are becoming of importance to a number of knowledge areas and sectors, including medicine, entertainment, design, engineering, education, arts and architecture, due to their accessibility and versatility. These technologies are changing the design of digital models, materials and manufacturing processes which enable to build previously unachievable physical objects. Since many constraints imposed on the design of objects have changed significantly, a growing research community is working on graphical tools and techniques to enable the conception, automation, production and usage of innovative and complex designs for fabrication. In the present work, we survey the state of the art of computer graphics contributions to functional fabrication design tools and techniques. By functional fabrication we understand the design and manufacture of physical objects which functionalities exploit the capabilities of digital fabrication technologies. These functionalities include improving the mechanics of a workpiece, producing articulated models, capturing aerodynamics, planning deformable workpieces and controlling the object’'s appearance and acoustics. The resulting design tools are clearly taking advantage of relevant computer graphics techniques. Furthermore, they are extending these techniques to realise new physical forms as well as bringing innovation to feed into the design space.Item Multi-View Ambient Occlusion for Enhancing Visualization of Raw Scanning Data(The Eurographics Association, 2016) Sabbadin, Manuele; Palma, Gianpaolo; Cignoni, Paolo; Scopigno, Roberto; Chiara Eva Catalano and Livio De LucaThe correct understanding of the 3D shape is a crucial aspect to improve the 3D scanning process, especially in order to perform high quality and as complete as possible 3D acquisitions on the field. The paper proposes a new technique to enhance the visualization of raw scanning data based on the definition in device space of a Multi-View Ambient Occlusion (MVAO). The approach allows improving the comprehension of the 3D shape of the input geometry and, requiring almost no preprocessing, it can be directly applied to raw captured point clouds. The algorithm has been tested on different datasets: high resolution Time-of-Flight scans and streams of low quality range maps from a depth camera. The results enhance the details perception in the 3D geometry using the multi-view information to make more robust the ambient occlusion estimation.Item Design and Fabrication of Grid-shells Mockups(The Eurographics Association, 2016) Tonelli, Davide; Pietroni, Nico; Cignoni, Paolo; Scopigno, Roberto; Giovanni Pintore and Filippo StancoStatics Aware Voronoi Grid-shells have been recently introduced in the Architectural Geometry field. These are innovative gridshells endowed with a polygonal topology, whose geometry is structurally optimized by means of a novel algorithm [PTP+15]. Although being structurally effective as proved in [TPP+16] and arguably aesthetically charming, so far these grid-shells have struggled to attract architects' interest. We propose a method to fabricate a mockup of the grid shell by using modern additive 3D printing and laser cutting technologies. We also show how the realised mockup can be used to perform a preliminary validation of the simulated static performances of the grid-shell structure.Item Tracing Field-Coherent Quad Layouts(The Eurographics Association and John Wiley & Sons Ltd., 2016) Pietroni, Nico; Puppo, Enrico; Marcias, Giorgio; Scopigno, Roberto; Cignoni, Paolo; Eitan Grinspun and Bernd Bickel and Yoshinori DobashiGiven a cross field over a triangulated surface we present a practical and robust method to compute a field aligned coarse quad layout over the surface. The method works directly on a triangle mesh without requiring any parametrization and it is based on a new technique for tracing field-coherent geodesic paths directly on a triangle mesh, and on a new relaxed formulation of a binary LP problem, which allows us to extract both conforming quad layouts and coarser layouts containing t-junctions. Our method is easy to implement, very robust, and, being directly based on the input cross field, it is able to generate better aligned layouts, even with complicated fields containing many singularities. We show results on a number of datasets and comparisons with state-of-the-art methods.