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Item A Virtual Character Posing System based on Reconfigurable Tangible User Interfaces and Immersive Virtual Reality(The Eurographics Association, 2018) Cannavò, A.; Lamberti, F.; Livesu, Marco and Pintore, Gianni and Signoroni, AlbertoComputer animation and, particularly, virtual character animation, are very time consuming and skill-intensive tasks, which require animators to work with sophisticated user interfaces. Tangible user interfaces (TUIs) already proved to be capable of making character animation more intuitive, and possibly more efficient, by leveraging the affordances provided by physical props that mimic the structure of virtual counterparts. The main downside of existing TUI-based animation solutions is the reduced accuracy, which is due partly to the use of mechanical parts, partly to the fact that, despite the adoption of a 3D input, users still have to work with a 2D output (usually represented by one or more views displayed on a screen). However, output methods that are natively 3D, e.g., based on virtual reality (VR), have been already exploited in different ways within computer animation scenarios. By moving from the above considerations and by building upon an existing work, this paper proposes a VR-based character animation system that combines the advantages of TUIs with the improved spatial awareness, enhanced visualization and better control on the observation point in the virtual space ensured by immersive VR. Results of a user study with both skilled and unskilled users showed a marked preference for the devised system, which was judged as more intuitive than that in the reference work, and allowed users to pose a virtual character in a lower time and with a higher accuracy.Item Extracting Ordered Iso-Geodesic Points on the Mesh(The Eurographics Association, 2020) Tortorici, Claudio; Werghi, Naoufel; Berretti, Stefano; Biasotti, Silvia and Pintus, Ruggero and Berretti, StefanoThe mesh manifold is one of the most used modalities for representing 3D objects. Although it provides a fully connected not oriented structure, it has some drawback when compared to the grid of pixels of a still image. Indeed, mesh manifolds do not hold any order information, neither locally nor globally, which makes some operation computationally expensive or even impossible. To unleash its potential and to benefit from its capability of representing the 3D information, further advancements have to be made in order to allow basic operations (i.e., convolution) and effective descriptor extraction. In this paper, we present our preliminary study on a new approach to extract Iso-Geodesic points on a mesh manifold. The approach can be applied in various applications, from feature extraction, to convolution operation and mesh reconstruction. It also revealed to be robust to variations of mesh surface and tessellation, providing an effective geodesic distance approximation.Item Yocto/GL: A Data-Oriented Library For Physically-Based Graphics(The Eurographics Association, 2019) Pellacini, Fabio; Nazzaro, Giacomo; Carra, Edoardo; Agus, Marco and Corsini, Massimiliano and Pintus, RuggeroIn this paper we present Yocto/GL, a software library for computer graphics research and education. The library is written in C++ and targets execution on the CPU, with support for basic math, geometry and imaging utilities, path tracing and file IO. What distinguishes Yocto/GL from other similar projects is its minimalistic design and data-oriented programming style, which makes the library readable, extendible, and efficient. We developed Yocto/GL to meet our need, as a research group, of a simple and reliable codebase that lets us experiment with ease on research projects of various kind. After many iterations carried out over a few years, we settled on a design that we find effective for our purposes. In the hope of making our efforts valuable for the community, we share our experience in the development and make the library publicly available.Item HT-based Recognition of Patterns on 3D Shapes Using a Dictionary of Mathematical Curves(The Eurographics Association, 2019) Romanengo, Chiara; Biasotti, Silvia; FALCIDIENO, BIANCA; Agus, Marco and Corsini, Massimiliano and Pintus, RuggeroCharacteristic curves play a fundamental role in the way a shape is perceived and illustrated. To address the curve recognition problem on surfaces, we adopt a generalisation of the Hough Transform (HT) which is able to deal with mathematical curves. In particular, we extend the set of curves so far adopted for curve recognition with the HT and propose a new dictionary of curves to be selected as templates. In addition, we introduce rules of composition and aggregation of curves into patterns, not limiting the recognition to a single curve at a time. Our method recognises various curves and patterns, possibly compound on a 3D surface. It selects the most suitable profile in a family of curves and, deriving from the HT, it is robust to noise and able to deal with data incompleteness. The system we have implemented is open and allows new additions of curves in the dictionary of functions already available.Item Evaluating Deep Learning Methods for Low Resolution Point Cloud Registration in Outdoor Scenarios(The Eurographics Association, 2021) Siddique, Arslan; Corsini, Massimiliano; Ganovelli, Fabio; Cignoni, Paolo; Frosini, Patrizio and Giorgi, Daniela and Melzi, Simone and Rodolà , EmanuelePoint cloud registration is a fundamental task in 3D reconstruction and environment perception. We explore the performance of modern Deep Learning-based registration techniques, in particular Deep Global Registration (DGR) and Learning Multiview Registration (LMVR), on an outdoor real world data consisting of thousands of range maps of a building acquired by a Velodyne LIDAR mounted on a drone. We used these pairwise registration methods in a sequential pipeline to obtain an initial rough registration. The output of this pipeline can be further globally refined. This simple registration pipeline allow us to assess if these modern methods are able to deal with this low quality data. Our experiments demonstrated that, despite some design choices adopted to take into account the peculiarities of the data, more work is required to improve the results of the registration.Item IMGD: Image-based Multiscale Global Descriptors of Airborne LiDAR Point Clouds Used for Comparative Analysis(The Eurographics Association, 2021) Sreevalsan-Nair, Jaya; Mohapatra, Pragyan; Singh, Satendra; Frosini, Patrizio and Giorgi, Daniela and Melzi, Simone and Rodolà , EmanueleBoth geometric and semantic information are required for a complete understanding of regions acquired as three-dimensional (3D) point clouds using the Light Detection and Ranging (LiDAR) technology. However, the global descriptors of such datasets that integrate both the information types are rare. With a focus on airborne LiDAR point clouds, we propose a novel global descriptor that transforms the point cloud from Cartesian to barycentric coordinate spaces. We use both the probabilistic geometric classification, aggregated from multiple scales, and the semantic classification to construct our descriptor using point rendering. Thus, we get an image-based multiscale global descriptor, IMGD. To demonstrate its usability, we propose the use of distribution distance measures between the descriptors for comparing the point clouds. Our experimental results demonstrate the effectiveness of our descriptor, when constructed of publicly available datasets, and on applying our selected distance measures.Item A Geometric Approach for Computing the Kernel of a Polyhedron(The Eurographics Association, 2021) Sorgente, Tommaso; Biasotti, Silvia; Spagnuolo, Michela; Frosini, Patrizio and Giorgi, Daniela and Melzi, Simone and Rodolà , EmanueleWe present a geometric algorithm to compute the geometric kernel of a generic polyhedron. The geometric kernel (or simply kernel) is defined as the set of points from which the whole polyhedron is visible. Whilst the computation of the kernel for a polygon has already been largely addressed in the literature, less has been done for polyhedra. Currently, the principal implementation of the kernel estimation is based on the solution of a linear programming problem. We compare against it on several examples, showing that our method is more efficient in analysing the elements of a generic tessellation. Details on the technical implementation and discussions on pros and cons of the method are also provided.Item Kernel-Based Sampling of Arbitrary Data(The Eurographics Association, 2020) Cammarasana, Simone; Patanè, Giuseppe; Biasotti, Silvia and Pintus, Ruggero and Berretti, StefanoPoint sampling is widely used in several Computer Graphics' applications, such as point-based modelling and rendering, image and geometric processing. Starting from the kernel-based sampling of signals defined on a regular grid, which generates adaptive distributions of samples with blue-noise property, we specialise this sampling to arbitrary data in terms of dimension and structure, such as signals, vector fields, curves, and surfaces. To demonstrate the novelties and benefits of the proposed approach, we discuss its applications to the resampling of 2D/3D domains according to the distribution of physical quantities computed as solutions to PDEs, and to the sampling of vector fields, 2D curves and 3D point sets. According to our experiments, the proposed sampling achieves a high approximation accuracy, preserves the features of the input data, and is computationally efficient.Item The Py3DViewer Project: A Python Library for fast Prototyping in Geometry Processing(The Eurographics Association, 2019) Cherchi, Gianmarco; Pitzalis, Luca; Frongia, Giovanni Laerte; Scateni, Riccardo; Agus, Marco and Corsini, Massimiliano and Pintus, RuggeroFast research and prototyping, nowadays, is shifting towards languages that allow interactive execution and quick changes. Python is very widely used for rapid prototyping. We introduce Py3DViewer, a new Python library that allows researchers to quickly prototype geometry processing algorithms by interactively editing and viewing meshes. Polygonal and polyhedral meshes are both supported. The library is designed to be used in conjunction with Jupyter environments, which allow interactive Python code execution and data visualization in a browser, thus opening up the possibility of viewing a mesh while editing the underlying geometry and topology.Item An Optimized Marker Layout for 3D Facial Motion Capture(The Eurographics Association, 2018) Will, A. D.; Martino, J. M. De; Bezerra, J.; Livesu, Marco and Pintore, Gianni and Signoroni, AlbertoFacial motion capture (Facial Mocap) has gained increasing attention from researchers and professionals from different areas of interest, including entertainment, face-to-face communication, and training. Facial Mocap allows straightforward capture of dynamic behavior of the face from live action, providing data that can be used to drive realistic animation of a 3D virtual face. Facial Mocap is an advantageous alternative to the direct and laborious manipulation of the face model. In particular, marker-based mocap technique acquires three-dimensional facial points trajectories by tracking markers fixed on the face of an actor. However, despite the existence of several empirical facial marker layouts, the ideal positioning of the markers is still an open question. This paper presents an optimization technique to calculate the quantity and positioning facial markers and establish their influences on the polygon mesh based on the correlation of markers in a dense layout. The technique generates an optimized marker layout discarding unnecessary markers and positioning the remaining ones.