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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 Automating Large 3D Dataset Publication in a Web-Based Multimedia Repository(The Eurographics Association, 2016) Potenziani, Marco; Fritsch, Bernhard; Dellepiane, Matteo; Scopigno, Roberto; Giovanni Pintore and Filippo StancoOnline publishing of almost every type of 3D data has become a quasi-standard routine. Nevertheless, the integration in a web page of a single 3D model, or of a predefined restricted set of models, raises different issues compared to an efficient and effective integration of thousands of them in an online repository. In this case it is mandatory to have an automatized pipeline to prepare and homogenize the dataset. The pipeline should be able to automatically wrap 3D data in all conditions, and display every single model with the best scene setup without any (or with a minimal) interaction by the database maintainers. This paper, retracing the steps of a recent real application case, aims at showing all the faced issues (and the adopted solutions) to publish a large and heterogeneous three-dimensional dataset in a web specialized repository. We want to introduce a valid and reusable strategy, starting from the description of the pipeline adopted for data pre-processing and moving to the choices made in the 3D viewer implementation. The paper concludes with a discussion on the actual state of the integration of 3D data with the other multimedia informative layers.Item ArchAIDE - Archaeological Automatic Interpretation and Documentation of cEramics(The Eurographics Association, 2016) Gualandi, Maria Letizia; Scopigno, Roberto; Wolf, Lior; Richards, Julian; Garrigos, Jaume Buxeda i; Heinzelmann, Michael; Hervas, Miguel Angel; Vila, Llorenc; Zallocco, Massimo; Chiara Eva Catalano and Livio De LucaThe goals of H2020 project "ArchAIDE: are to support the classification and interpretation work of archaeologists with innovative computer-based tools, able to provide the user with features for the semi-automatic description and matching of potsherds over the huge existing ceramic catalogues. Pottery classification is of fundamental importance for the comprehension and dating of the archaeological contexts, and for understanding production, trade flows and social interactions, but it requires complex skills and it is a very time consuming activity, both for researchers and professionals. The aim of ArchAIDE is to support the work of archaeologists, in order to meet real user needs and generate economic benefits, reducing time and costs. This would create societal benefits from cultural heritage, improving access, re-use and exploitation of the digital cultural heritage in a sustainable way. These objectives will be achieved through the development of: - an as-automatic-as-possible procedure to transform the paper catalogues in a digital description, to be used as a data pool for search and retrieval process; - a tool (mainly designed for mobile devices) that will support archaeologists in recognizing and classifying potsherds during excavation and post-excavation analysis, through an easy-to-use interface and efficient algorithms for characterisation, search and retrieval of the visual/geometrical correspondences; - an automatic procedure to derive a complete potsherds identity card by transforming the data collected into a formatted electronic document, printable or visual; - a web-based real-time data visualisation to improve access to archaeological heritage and generate new understanding; - an open archive to allow the archival and re-use of archaeological data, transforming them into common heritage and permitting economic sustainability. Those tools will be tested and assessed on real-cases scenarios, paving the way to future exploitation.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 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 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.Item Fast Metric Acquisition with Mobile Devices(The Eurographics Association, 2016) Garro, Valeria; Pintore, Giovanni; Ganovelli, Fabio; Gobbetti, Enrico; Scopigno, Roberto; Matthias Hullin and Marc Stamminger and Tino WeinkaufWe present a novel algorithm for fast metric reconstruction on mobile devices using a combination of image and inertial acceleration data. In contrast to previous approaches to this problem, our algorithm does not require a long acquisition time or intensive data processing and can be implemented entirely on common IMU-enabled tablet and smartphones. The method recovers real world units by comparing the acceleration values from the inertial sensors with the ones inferred from images. In order to cope with IMU signal noise, we propose a novel RANSAC-like strategy which helps to remove the outliers. We demonstrate the effectiveness and the accuracy of our method through an integrated mobile system returning point clouds in metric scale.