Italian Chapter Conference 2017 - Smart Tools and Apps in computer Graphics

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    A 3 Cent Recognizer: Simple and Effective Retrieval and Classification of Mid-air Gestures from Single 3D Traces
    (The Eurographics Association, 2017) Caputo, Fabio Marco; Prebianca, Pietro; Carcangiu, Alessandro; Spano, Lucio D.; Giachetti, Andrea; Andrea Giachetti and Paolo Pingi and Filippo Stanco
    In this paper we present a simple 3D gesture recognizer based on trajectory matching, showing its good performances in classification and retrieval of command gestures based on single hand trajectories. We demonstrate that further simplifications in porting the classic "1 dollar" algorithm approach from the 2D to the 3D gesture recognition and retrieval problems can result in very high classification accuracy and retrieval scores even on datasets with a large number of different gestures executed by different users. Furthermore, recognition can be good even with heavily subsampled path traces and with incomplete gestures.
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    3D Reconstruction of Facade and the Statues of the Church ''Maria Santissima dell'Elemosina'' in Biancavilla
    (The Eurographics Association, 2017) Tomasello, Simone Federico; Pazzi, Miriam Caterina; Andrea Giachetti and Paolo Pingi and Filippo Stanco
    3D modelling plays a key role in the reconstruction of cultural heritage assets. It allows to give an idea of the original condition of a cultural heritage before time and weathering effects. This paper presents the 3D reconstruction of the church ''Maria Santissima dell'Elemosina'' through various software for modelling, as well as the acquisition and processing of elements. High resolution photos has been employed for faithful reproduction of the models details.
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    A Digital Approach for the Study of Roman Signacula From Syracuse, Sicily
    (The Eurographics Association, 2017) Tanasi, Davide; Milotta, Filippo L. M.; Gradante, Ilenia; Stanco, Filippo; Kaplan, Howard; Andrea Giachetti and Paolo Pingi and Filippo Stanco
    In the last decade the epigraphists have grown a new interest in signacula, a class of artifacts for a long time neglected. This has brought numerous contributions devoted to the different regional contexts, along with reflections on methodological questions, not to mention the momentum towards the digitizing of a corpus which counts at least 3,500 pieces, confirming the great potential of these artifacts in providing information related not only to the economy and to the administration of the ''res'', both in public and private sphere, but also about the profile of the signacula holders. In this scenario, a specific research question has been inspired by the Sicilian seals - about 60 signacula and a dozen impressions left by seals on mortar in burial contexts: it is possible to identify unequivocally a signaculum through its impression? Given for granted that the use of 3D documentation will bring along effective results in terms of improved readability of signacula and seals, the aim of this contribute is to establish a protocol for a semi-automatic matching between 3D models of seals and 3D models of impressions. As part of a preliminary scanning campaign of Late Roman impressions on mortars and metal seals from the catacombs of Syracuse, two bronze metal seals were digitized with a NextEngine 3D triangulation laser scanner and subsequently 3D printed with liquid resin with a Formlabs Form 2 SLA high resolution printer. The casts obtained, were experimentally used to create a set of impressions on mortar using different degrees and angles of pressure, in order to create similar but still different stamps. During the next step, the impressions were 3D scanned and used as ground truth for the outlined semi-automatic procedure of matching with the seals. In MeshLab environment, the 3d models of seals and impressions were manually aligned and then the distance between two sets of 3D points was measured using the filter Hausdorff distance in order to validate a matching. This successful exercise could open the way to the proposal of creating a virtual edition of signacula with 3D models metadata. Furthermore, a research agenda may include the design of a machine learning algorithm for matching of 3D meshes.
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    Heat Flow Based Relaxation of n Dimensional Discrete Hyper Surfaces
    (The Eurographics Association, 2017) Livesu, Marco; Andrea Giachetti and Paolo Pingi and Filippo Stanco
    We consider the problem of relaxing a discrete (n - 1) dimensional hyper surface defining the boundary between two adjacent n dimensional regions in a discrete segmentation. This problem often occurs in computer graphics and vision, where objects are represented by discrete entities such as pixel/voxel grids or polygonal/polyhedral meshes. A common approach consists in assigning to each element of the domain a value (or label). Elements sharing the same label belong to the same region, whereas elements with different labels belong to different regions. Segmentation boundaries are therefore only intrinsically defined, and amount to the union of the interfaces between adjacent elements having different label, which tend to be geometrically poor and expose a typical jagged behavior. We propose a relaxation scheme that replaces the original boundary with a smoother version of it, defined as the level set of a continuous function. The problem has already been considered in recent years, but current methods are specifically designed to relax curves on discrete 2-manifolds embedded in R3, and do not clearly scale to multiple discrete representations or to higher dimensions. Our biggest contribution is a smoothing operator that is based only on three canonical differential operators: namely the Laplacian, gradient and divergence. These operators are ubiquitous in applied mathematics, are available for a variety of discretization choices, and exist in any dimension. To the best of the author’'s knowledge, this is the first intrinsically dimension-independent method, and can be used to relax curves on 2-manifolds, surfaces in R3, or even hyper-surfaces in Rn. As such, not only it is useful to refine the boundaries of discrete segmentations, but also for applications like data mining, where clustering in high dimensional spaces often occur, and the refinement of the clusters' boundaries may be beneficial for classification algorithms.
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    Perimeter Detection in Sketched Drawings of Polyhedral Shapes
    (The Eurographics Association, 2017) Company, Pedro; Varley, Peter A. C.; Plumed, Raquel; Andrea Giachetti and Paolo Pingi and Filippo Stanco
    This paper describes a new "envelope" approach for detecting object perimeters in line-drawings vectorised from sketches of polyhedral objects. Existing approaches for extracting contours from digital images are unsuitable for Sketch-Based Modelling, as they calculate where the contour is, but not which elements of the line-drawing belong to it. In our approach, the perimeter is described in terms of lines and junctions (including intersections and T-junctions) of the original line drawing.
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    Polycube-based Decomposition for Fabrication
    (The Eurographics Association, 2017) Fanni, Filippo A.; Cherchi, Gianmarco; Scateni, Riccardo; Andrea Giachetti and Paolo Pingi and Filippo Stanco
    In recent years, fabrication technologies developed at a very fast pace. However, some limitations on shape and dimension still apply both to additive and subtractive manufacturing, and one way to bypass them could be the subdivision of the object to build. We present here a simple algorithm, based on the polycube representation of the original shape, able to decompose any model into simpler portions that are better fabricable. The shape is first mapped in a polycube and, then, split to take advantage of the simple polycube subdivision, thus having, quite easily, a partition of the model at hand. The main aim of this work is to study and analyse pros and cons of this simple subdivision scheme for fabrication, in view of using both the additive and subtractive pipelines. The proposed subdivision scheme is computationally light and it produces quite good results, especially when it is applied to models that can be easily decomposed in a small collection of cuboids. The obtained subdivisions are suitable for 3D printing.
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    A Seamless Pipeline for the Acquisition of the Body Shape: the Virtuoso Case Study
    (The Eurographics Association, 2017) Saba, Marianna; Sorrentino, Fabio; Muntoni, Alessandro; Casti, Sara; Cherchi, Gianmarco; Carcangiu, Alessandro; Corda, Fabrizio; Murru, Alessio; Spano, Lucio Davide; Scateni, Riccardo; Vitali, Ilaria; Salvetti, Ovidio; Magrini, Massimo; Villa, Andrea; Carboni, Andrea; Pascali, Maria Antonietta; Andrea Giachetti and Paolo Pingi and Filippo Stanco
    In this paper, we describe the design and the implementation of the demonstrator for the Virtuoso project, which aims at creating seamless support for fitness and wellness activities in touristic resort.We define the objectives of the user interface, the hardware and software setup, showing how we combined and exploited consumer-level devices for supporting 3D body scan, contact-less acquisition of physical parameters, exercise guidance and operator support.
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    Single-Handed vs. Two Handed Manipulation in Virtual Reality: A Novel Metaphor and Experimental Comparisons
    (The Eurographics Association, 2017) Caputo, Fabio Marco; Emporio, Marco; Giachetti, Andrea; Andrea Giachetti and Paolo Pingi and Filippo Stanco
    In this paper we present a novel solution for single-handed deviceless object manipulation (e.g. picking/translating, rotating and scaling) in immersive visualization environments. The new method is based on degree of freedom (DOF) separation and on the idea of activating unambiguous gesture recognition when the hand is close to the object, giving visual feedback about gesture realization and available transitions. Furthermore, it introduces a novel metaphor, the "knob", to map hand rotation onto object rotation around selected axes. The solution was tested with users on a classical visualization task related to finding a point of interest in a 3D object and compared with the well known "Handlebar" metaphor. The metaphor shows a reasonable usability, even if not comparable with the bi- manual solution, particularly suited for the tested task. However, given the relevant improvements with task repetitions and the technical issues that can be solved improving the performances, the method seems to be a viable solution for deviceless single-hand manipulation.
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    Smart Tools and Applications in computer Graphics - Eurographics Italian Chapter Conference 2017: Frontmatter
    (Eurographics Association, 2017) Giachetti, Andrea; Pingi, Paolo; Stanco, Filippo; Andrea Giachetti and Paolo Pingi and Filippo Stanco
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    The Social Picture: Advanced Image Analysis Applications
    (The Eurographics Association, 2017) Milotta, Filippo L. M.; Bellocchi, Michele; Battiato, Sebastiano; Andrea Giachetti and Paolo Pingi and Filippo Stanco
    In The Social Picture (TSP) an huge amount of crowdsourced social images can be collected and explored. We distinguish three main kind of events: public, private and cultural heritage related ones. The framework embeds a number of advanced Computer Vision algorithms, able to capture the visual content of images and organize them in a semantic way. In this paper we employ VisualSFM (VSFM) to add new features in TSP through the computation of a 3D sparse reconstruction of a collection within TSP. VisualSFM creates a N-View Match (NVM) file as output. Starting from this NVM file, which characterizes the 3D sparse reconstruction, we are able to build two important relationships: the one between cameras and points and the one between cameras themselves. Using these relationships, we implemented two advanced Image Analysis applications. In the first one, we consider the cameras as nodes in a fully connected graph in which the edges weights are equal to the number of matches between cameras. The spanning tree of this graph is used to explore images in a meaningful way, obtaining a scene summarization. In the second application, we define three kinds of density maps with relation to image features: density map, weighted-density map and social-weighted-density map. Results of a test conducted on a collection from TSP is shown.
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    User Interaction Feedback in a Hand-Controlled Interface for Robot Team Tele-operation Using Wearable Augmented Reality
    (The Eurographics Association, 2017) Cannavò, Alberto; Lamberti, Fabrizio; Andrea Giachetti and Paolo Pingi and Filippo Stanco
    Continuous advancements in the field of robotics and its increasing spread across heterogeneous application scenarios make the development of ever more effective user interfaces for human-robot interaction (HRI) an extremely relevant research topic. In particular, Natural User Interfaces (NUIs), e.g., based on hand and body gestures, proved to be an interesting technology to be exploited for designing intuitive interaction paradigms in the field of HRI. However, the more sophisticated the HRI interfaces become, the more important is to provide users with an accurate feedback about the state of the robot as well as of the interface itself. In this work, an Augmented Reality (AR)-based interface is deployed on a head-mounted display to enable tele-operation of a remote robot team using hand movements and gestures. A user study is performed to assess the advantages of wearable AR compared to desktop-based AR in the execution of specific tasks.
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    Visual Analysis of Glycogen Derived Lactate Absorption in Dense and Sparse Surface Reconstructions of Rodent Brain Structures
    (The Eurographics Association, 2017) Calì, Corrado; Agus, Marco; Gagnon, Nicholas; Hadwiger, Markus; Magistretti, Pierre J.; Andrea Giachetti and Paolo Pingi and Filippo Stanco
    Astrocytes are the most abundant type of glial cells of the central nervous system; their involvement in brain functioning, from synaptic to network level, is to date a matter of intense research. A well-established function of astroglial cells, among others, is the metabolic support of neurons. Recently, it has been shown that during tasks like learning and long-term memory formation, synapses sustain their metabolic needs using lactate, a compound that astrocytes can synthesize from glycogen, a molecule that stores glucose, rather than glucose itself. Aforementioned role of astrocytes, as energy reservoir to neurons, is challenging the classic paradigms of neuro-energetic research. Understanding their morphology at nano-scale resolution is therefore a fundamental research challenge with enormous implications on many branches of neuroscience research, such as the study of neuro-degenerative and cognitive disorders. Here, we present an illustrative visualization technique customized for the analysis of the interaction of astrocytic glycogen on surrounding neurites in order to formulate hypotheses on the energy absorption mechanisms. The method integrates a high-resolution surface reconstruction of neurites and the energy sources in form of glycogen granules, and computes an absorption map according to a radiance transfer mechanism. The technique is built on top of a framework for processing and rendering triangulated surface models, and it is used for real-time 3D exploration and inspection of the neural structures paired with the energy sources. The resulting visual representation provides an immediate and comprehensible illustration of the areas in which the probability of lactate shuttling is higher. This method has been further employed for testing neuroenergetics hypotheses about the utilization of glycogen during synaptic development.