Italian Chapter Conference 2018 - Smart Tools and Apps in computer Graphics

Permanent URI for this collection

https://diglib.eg.org/handle/10.2312/2632667

Browse

Browsing Italian Chapter Conference 2018 - Smart Tools and Apps in computer Graphics by Issue Date

Filter results by year or month
Now showing 1 - 15 of 15
  • No Thumbnail Available
    Item
    Frontmatter: STAG 2018: Smart Tools and Applications in computer Graphics
    (The Eurographics Association, 2018) Signoroni, Alberto; Livesu, Marco; Agus, Marco; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
  • No Thumbnail Available
    Item
    Direct Scalar Field - to - Truss Representation and Stress Simulation of Open Pore Domains
    (The Eurographics Association, 2018) Munoz, J. M.; Ruiz-Salguero, O.; Montoya-Zapata, D.; Cortes, C.; Cadavid, C.; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
    In the domain of lattice and porous material geometric modeling, the problem of data size is central. When using full 3D manifold Boundary Representations (BRep), even the smallest domains engender staggering amounts of 3D finite elements. A partial solution has been implemented, which represents slender solid neighborhoods with non-manifold Boolean union of 1- manifolds (curves) and/or 2-manifolds (surfaces), added with thickness information, called 1.5D and 2.5D models, respectively. Automatic applications of these techniques requires the estimation of the medial axis of the porous media, to produce a truss or frame FEA. Previous works require explicit synthesis of the skin of the porous domain. This manuscript presents an alternative in which the medial axis and thus the 1.5D (truss) representation of the porous domain is directly obtained from the scalar field (i.e., Computer Tomography -CT-) of the domain, thus avoiding the explicit calculation of the domain skin. The manuscript also presents the noise removal and linearization of the medial axis data, to obtain the skeleton truss graph (including bar radii), that represents the porous domain. Shear and tension load simulations are conducted with the Truss model, showing that the generated model can be used in FEA software. Future work is required in extending this concept to lattice materials, where the medial axis includes surfaces and not only curves, as in this manuscript.
  • No Thumbnail Available
    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, Alberto
    Facial 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.
  • No Thumbnail Available
    Item
    CageLab: an Interactive Tool for Cage-Based Deformations
    (The Eurographics Association, 2018) Casti, S.; Corda, F.; Livesu, M.; Scateni, R.; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
    Posing a digital character by acting on the vertices of a coarse control cage is, after skeleton-based, probably the most widely used technique for digital animation. While skeleton-based techniques have been deeply researched and a variety of industrial and academic tools are available for it, cage-based techniques have historically received less attention. In recent years we observed an increasing interest in the field, which results in a growing number of publications both on algorithms for automatic or semi-automatic cage generation, and for smooth barycentric coordinates for general polyhedral meshes. We introduce CageLab: a novel research-oriented software tool that allows scholars and practitioners in general to get acquainted with cagebased animation in a lightweight and easy to use environment. Users can: (i) load digital characters and their associated cages, applying character deformations with a selection of the most widely used barycentric coordinates available in literature; (ii) compare alternative cages for a given digital character; (iii) compare alternative barycentric coordinates w.r.t their smoothness and locality within the cage; (iv) use CageLab for educational purposes, or to produce images and videos for scientific articles. We publicly release the tool to the community, with the hope to support this growth, and possibly foster even more research in the field.
  • No Thumbnail Available
    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, Alberto
    Computer 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.
  • No Thumbnail Available
    Item
    Slice2mesh: Meshing Sliced Data for the Simulation of AM Processes
    (The Eurographics Association, 2018) Livesu, M.; Cabiddu, D.; Attene, M.; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
    Accurately simulating Additive Manufacturing (AM) processes is useful to predict printing failures and test 3D printing without wasting precious resources, both in terms of time ad material. In AM the object to be fabricated is first cut into a set of slices aligned with the build direction, and then printed, depositing or solidifying material one layer on top of the other. To guarantee accurate simulations, it is therefore necessary to encode the temporal evolution of the shape to be printed within the simulation domain. We introduce slice2mesh, to the best of our knowledge the first software capable of turning a sliced object directly into a volumetric mesh. Our tool inputs a set of slices and produces a tetrahedral mesh that endows each slice in its connectivity. An accurate representation of the simulation domain at any time during the print can therefore be easily obtained by filtering out the slices yet to be processed. slice2mesh also features a flexible mesh generation system for external supports, and allows the user to trade accuracy for simplicity by producing approximate simulation domains obtained by filtering the object in slice space.
  • No Thumbnail Available
    Item
    A Study on Natural 3D Shape Manipulation in VR
    (The Eurographics Association, 2018) Cordeiro, E.; Giannini, F.; Monti, M.; Mendes, D.; Ferreira, A.; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
    Current immersive modeling environments use non-natural tools and interfaces to support traditional shape manipulation operations. In the future, we expect the availability of natural methods of interaction with 3D models in immersive environments to become increasingly important in several industrial applications. In this paper, we present a study conducted on a group of potential users with the aim of verifying if there is a common strategy in gestural and vocal interaction in immersive environments when the objective is modifying a 3D shape model. The results indicate that users adopt different strategies to perform the different tasks but in the execution of a specific activity it is possible to identify a set of similar and recurrent gestures. In general, the gestures made are physically plausible. During the experiment, the vocal interaction was used quite rarely and never to express a command to the system but rather to better specify what the user was doing with gestures.
  • No Thumbnail Available
    Item
    Indicators Basis for Functional Shape Analysis
    (The Eurographics Association, 2018) Melzi, S.; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
    Step functions are widely used in several applications from geometry processing and shape analysis. Shape segmentation, partial matching and self similarity detection just to name a few. The standard signal processing tools do not allow us to fully handle this class of functions. The classical Fourier series, for instance, does not give a good representation for these non smooth functions. In this paper we define a new basis for the approximation and transfer of the step functions between shapes. Our definition is fully spectral, allowing for a concise representation and an efficient computation. Furthermore our basis is specifically built in order to enhance its use in combination with the functional maps framework. The functional approach also enable us to handle shape deformations. Thanks to that our basis achieves a large improvement not only in the approximation of step functions but also in the transfer, exploiting the functional maps framework. We perform a large set of experiments showing the improvement achieved by the proposed basis in the approximation and transfer of step functions and its stability with respect to non isometric deformations.
  • No Thumbnail Available
    Item
    Adaptive Environmental Sampling: The Interplay Between Geostatistics and Geometry
    (The Eurographics Association, 2018) Berretta, S.; Cabiddu, D.; Pittaluga, S.; Mortara, M.; Spagnuolo, M.; Zuccolini, M. Vetuschi; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
    In environmental surveys a large sampling effort is required to produce accurate geostatistical maps representing the distribution of environmental variables, and the analysis of each sample is often expensive. Typically, the sample locations are completely specified in the survey design phase, prior to data-collection. Usually, the sampling points are located on a regular grid, or along directions that are selected with respect to any a-priori knowledge of the expert. No feedback is available during the survey. In this paper, we present a different sampling strategy, namely adaptive sampling. Our approach exploits geostatistics constructs in order to determine on-the fly the next best sample location. After initializing the system with few sampling points, an iterative routine predicts the variable distribution from the data sampled so far, and suggests the next sample to be acquired in order to optimize the uncertainty of the estimates. At every iteration a new sample is acquired, and the variable distribution map is refined, along with the uncertainty map related to that distribution. Our method allows to build a representation of the survey area as precise as the one provided by the traditional methods, but with less samples, thus reducing both time and costs of the survey. We show a preliminary evaluation of the adaptive strategy in the bi-dimensional case based on a synthetic scenario, and describe the generalization of these encouraging results to the full 3D domain in the concrete setting of water quality monitoring. A proper geometric representation of the three dimensional survey area, coupled with a proper visualization of distribution and related uncertainty, will provide real-time feedback during the survey.
  • No Thumbnail Available
    Item
    Hyperquadrics for Shape Analysis of 3D Nanoscale Reconstructions of Brain Cell Nuclear Envelopes
    (The Eurographics Association, 2018) Agus, M.; Calì, C.; Morales, A. Tapia; Lehväslaiho, H. O.; Magistretti, P. J.; Gobbetti, E.; Hadwiger, M.; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
    Shape analysis of cell nuclei is becoming increasingly important in biology and medicine. Recent results have identified that the significant variability in shape and size of nuclei has an important impact on many biological processes. Current analysis techniques involve automatic methods for detection and segmentation of histology and microscopy images, and are mostly performed in 2D. Methods for 3D shape analysis, made possible by emerging acquisition methods capable to provide nanometric-scale 3D reconstructions, are, however, still at an early stage, and often assume a simple spherical shape. We introduce here a framework for analyzing 3D nanoscale reconstructions of nuclei of brain cells (mostly neurons), obtained by semiautomatic segmentation of electron micrographs. Our method considers an implicit parametric representation customizing the hyperquadrics formulation of convex shapes. Point clouds of nuclear envelopes, extracted from image data, are fitted to our parametrized model, which is then used for performing statistical analysis and shape comparisons. We report on the preliminary analysis of a collection of 92 nuclei of brain cells obtained from a sample of the somatosensory cortex of a juvenile rat.
  • No Thumbnail Available
    Item
    Simplification of Shapes for Fabrication with V-Groove Milling Tools
    (The Eurographics Association, 2018) Muntoni, A.; Scalas, A.; Nuvoli, S.; Scateni, R.; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
    We introduce here a pipeline for simplifying digital 3D shapes with the aim of fabricating them using 2D polygonal flat parts. Our method generates shapes that, once unfolded, can be fabricated with CNC milling machines using special tools called V-Grooves. These tools make V-shaped furrows at given angles depending on the shape of the used tool. Milling the edges of each flat facet simplifies the manual assembly that consists only in folding the facets at the desired angle between the adjacent facets. Our method generates simplified shapes where every dihedral angle between adjacent facets belongs to a restricted set, thus making the assembly process quicker and more straightforward. Firstly, our method automatically computes a simplification of the model, iterating local changes on a triangle mesh generated by applying the Marching Cubes algorithm on the original mesh. The user performs a second manual simplification using a tool that removes spurious facets. Finally, we use a simple unfolding algorithm which flattens the polygonal facets onto the 2D plane, so that a CNC milling machine can fabricate it with a sheet of rigid material.
  • No Thumbnail Available
    Item
    Fast Centroidal Deformation for Large Mesh Models
    (The Eurographics Association, 2018) Morsucci, A.; Centin, M.; Signoroni, A.; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
    We present an algorithm that allows fast non-linear deformation editing on high-quality meshes. The proposed Fast Centroidal Deformation (FCD) method is based on a multi-resolution framework, where a centroidal deformation graph is built over the mesh in order to allow fast non-linear optimization at a coarse scale. The resulting deformation is then propagated to the initial dense mesh by exploiting the relationship between the constructed deformation graph and the input mesh through a mapping function that unifies local rotations and global translations without the need of solving a system composed by a number of linear equations of the same magnitude of the number of vertices of the mesh. A number of flexible user constraints can be imposed in the deformation through a handle-based metaphor where the user can redefine the position and orientation of single control points or entire portions of the input model. The proposed method addresses the obstacle of non-linear deformation on meshes composed by millions of vertices and is compared with the reference deformation techniques, showing significant improvements in terms of computational efficiency without renouncing to the quality of the results given by non-linear methods.
  • No Thumbnail Available
    Item
    Knee Up: an Exercise Game for Standing Knee Raises by Motion Capture with RGB-D Sensor
    (The Eurographics Association, 2018) Kiziltas, D.; Celikcan, U.; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
    In this work, we present the design and the implementation of Knee Up, an exergame that promotes knee health via standing knee raises exercises. It allows users to exercise at home and perform the exercise in a gaming environment. By motion capture using RGB-D data, estimated positions of the user's skeletal joints are acquired and processed in real-time. For the game, 3D virtual environments have been created with gamification elements so that users can enjoy more interactive and engaging exercise sessions. The game facilitates to evaluate the quality of performed standing knee raises exercise through a rule-based recognition algorithm and, in return, to provide timely feedback. A formal user study was conducted in order to assess the usability and gamification aspects of Knee Up. Study results demonstrate that Knee Up is generally well-received in terms of usability, engagement, ease of learning-to-play, and exercise sustainability; and validate that the rule-based recognition algorithm works satisfactorily well.
  • No Thumbnail Available
    Item
    Pixel-based Wake Interaction and Power Estimation for a Wind Farm with Irregular Boundary
    (The Eurographics Association, 2018) Ohlsen, G.; Ruiz-Salguero, O.; Full, T.; Acosta, D.; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
    In the domain of generation of wind turbine energy, it is central to correctly estimate the interactions among the various turbines in a wind turbine farm. The spatial super-position of turbine wind wakes determines the wind conditions that each turbine in the farm is exposed to and its power output. The current state of the art represents the turbine wakes as a 2D real-valued polygonal trapezoid. The interactions among wakes imply Boolean operations among many trapezoids, producing an intractable fragmentation of the wake intersection and domain regions. The plan (2D) view of the terrain with this wake polygon fragmentation is then used to estimate the effective wind that each turbine receives. This calculation leads to cumbersome computation, which is even more impractical if 3D representations of the terrain, wakes and wind are needed. In response to these limitations, this manuscript presents a method in which the 2D turbine wakes are located on a terrain with holes and exclusion zones bounded by 2D polygons, considering wind direction and turbine array basic specifications. Then, a discretized or pixel approximation of the terrain and wake superposition is calculated using discrete levels of the turbine velocity deficits. This process allows a practical approximation of the power output of each turbine and of the full turbine set. The wake interaction and terrain boundaries are then texture - mapped onto the 3D representation of the terrain, for visualization purposes. As an application, an example of a complex polygonal terrain turbine farm is optimized for maximal power output. This discrete, image - based calculation is particularly convenient in a circumstance in which graphics hardware and GPU processors become increasingly available and efficient, in laptop and mobile devices. This investigation opens research opportunities in mixtures of turbine types, 3D modeling of wind / terrain interaction, and accelerated calculation and visualization with GPU hardware.
  • No Thumbnail Available
    Item
    Gradient Field Estimation on Triangle Meshes
    (The Eurographics Association, 2018) Mancinelli, C.; Livesu, M.; Puppo, E.; Livesu, Marco and Pintore, Gianni and Signoroni, Alberto
    The estimation of the differential properties of a function sampled at the vertices of a discrete domain is at the basis of many applied sciences. In this paper, we focus on the computation of function gradients on triangle meshes. We study one face-based method (the standard the facto), plus three vertex based methods. Comparisons regard accuracy, ability to perform on different domain discretizations, and efficiency. We performed extensive tests and provide an in-depth analysis of our results. Besides some behaviour that is common to all methods, in our study we found that, considering both accuracy and efficiency, some methods are preferable to others. This directly translates to useful suggestions for the implementation of gradient estimators in research and industrial code.