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Item 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 StancoIn 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.Item STRONGER: Simple TRajectory-based ONline GEsture Recognizer(The Eurographics Association, 2021) Emporio, Marco; Caputo, Ariel; Giachetti, Andrea; Frosini, Patrizio and Giorgi, Daniela and Melzi, Simone and Rodolà , EmanueleIn this paper, we present STRONGER, a client-server solution for the online gesture recognition from captured hands' joints sequences. The system leverages a CNN-based recognizer improving current state-of-the-art solutions for segmented gestures classification, trained and tested for the online gesture recognition task on a recent benchmark including heterogeneous gestures. The recognizer provides good classification accuracy and a limited number of false positives on most of the gesture classes of the benchmark used and has been used to create a demo application in a Mixed Reality scenario using an Hololens 2 optical see through Head-Mounted Display with hand tracking capability.Item TESTIMAGES: a Large-scale Archive for Testing Visual Devices and Basic Image Processing Algorithms(The Eurographics Association, 2014) Asuni, Nicola; Giachetti, Andrea; Andrea GiachettiWe present the TESTIMAGES archive, a huge and free collection of sample images designed for analysis and quality assessment of different kinds of displays (i.e. monitors, televisions and digital cinema projectors) and image processing tecnhiques. The archive includes more than 2 million images originally acquired and divided in four different categories: SAMPLING and SAMPLING_PATTERNS (aimed at testing resampling algorithms), COLOR (aimed at testing color rendering on different displays) and PATTERNS (aimed at testing the rendering of standard geometrical patterns). The archive is currently online as a SourceForge project and, even if not yet publicized in the scientific community, it has already been used in different contexts and cited in scientific publications. We plan to extend the archive including datasets for other kinds of specific analyses.Item Smart Tools and Applications in Graphics - Eurographics Italian Chapter Conference: Frontmatter(The Eurographics Association, 2024) Caputo, Ariel; Garro, Valeria; Giachetti, Andrea; Castellani, Umberto; Dulecha, Tinsae Gebrechristos; Caputo, Ariel; Garro, Valeria; Giachetti, Andrea; Castellani, Umberto; Dulecha, Tinsae GebrechristosItem 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 StancoItem Approximating Shapes with Standard and Custom 3D Printed LEGO Bricks(The Eurographics Association, 2021) Fanni, Filippo Andrea; Dal Bello, Alberto; Sbardellini, Simone; Giachetti, Andrea; Frosini, Patrizio and Giorgi, Daniela and Melzi, Simone and Rodolà , EmanueleIn this paper, we present a work-in-progress aimed at developing a pipeline for the fabrication of shapes reproducing digital models with a combination of standard LEGO bricks and 3D printed custom elements. The pipeline starts searching for the ideal alignment of the 3D model with the brick grid. It then employs a novel approach for shape "legolization" using a outside-in heuristic to limit critical configuration, and separates an external shell and an internal part. Finally, it exploits shape booleans to create the external custom parts to be 3D printed.Item Practical Free-form RTI Acquisition with Local Spot Lights(The Eurographics Association, 2016) Pintus, Ruggero; Ciortan, Irina Mihaela; Giachetti, Andrea; Gobbetti, Enrico; Giovanni Pintore and Filippo StancoWe present an automated light calibration pipeline for free-form acquisition of shape and reflectance of objects using common off-the-shelf illuminators, such as LED lights, that can be placed arbitrarily close to the objects. We acquire multiple digital photographs of the studied object shot from a stationary camera. In each photograph, a light is freely positioned around the object in order to cover a wide variety of illumination directions. While common free-form acquisition approaches are based on the simplifying assumptions that the light sources are either sufficiently far from the object that all incoming light can be modeled using parallel rays, or that lights are local points emitting uniformly in space, we use the more realistic model of a scene lit by a moving local spot light with exponential fall-off depending on the cosine of the angle between the spot light optical axis and the illumination direction, raised to the power of the spot exponent. We recover all spot light parameters using a multipass numerical method. First, light positions are determined using standard methods used in photometric stereo approaches. Then, we exploit measures taken on a Lambertian reference planar object to recover the spot light exponent and the per-image spot light optical axis; we minimize the difference between the observed reflectance and the reflectance synthesized by using the near-field Lambertian equation. The optimization is performed in two passes, first generating a starting solution and then refining it using a Levenberg-Marquardt iterative minimizer. We demonstrate the effectiveness of the method based on an error analysis performed on analytical datasets, as well as on real-world experiments.Item Remote and Deviceless Manipulation of Virtual Objects in Mixed Reality(The Eurographics Association, 2023) Caputo, Ariel; Bartolomioli, Riccardo; Giachetti, Andrea; Banterle, Francesco; Caggianese, Giuseppe; Capece, Nicola; Erra, Ugo; Lupinetti, Katia; Manfredi, GildaDeviceless manipulation of virtual objects in mixed reality (MR) environments is technically achievable with the current generation of Head-Mounted Displays (HMDs), as they track finger movements and allow you to use gestures to control the transformation. However, when the object manipulation is performed at some distance, and when the transform includes scaling, it is not obvious how to remap the hand motions over the degrees of freedom of the object. Different solutions have been implemented in software toolkits, but there are still usability issues and a lack of clear guidelines for the interaction design. We present a user study evaluating three solutions for the remote translation, rotation, and scaling of virtual objects in the real environment without using handheld devices. We analyze their usability on the practical task of docking virtual cubes on a tangible shelf from varying distances. The outcomes of our study show that the usability of the methods is strongly affected by the use of separate or integrated control of the degrees of freedom, by the use of the hands in a symmetric or specialized way, by the visual feedback, and by the previous experience of the users.Item Outside-in Priority-based Approximation of 3D Models in LEGO Bricks(The Eurographics Association, 2022) Fanni, Filippo Andrea; Rossi, Elisa De; Giachetti, Andrea; Cabiddu, Daniela; Schneider, Teseo; Allegra, Dario; Catalano, Chiara Eva; Cherchi, Gianmarco; Scateni, RiccardoIn this paper, we discuss the problem of converting a 3D mesh into an assembly of LEGO blocks. The major challenge of this task is how to aggregate the voxels derived by the shape discretization into a set of standard bricks guaranteeing global connectivity. We propose an outside-in priority-based heuristic method based on the analysis of the critical regions that are more likely to cause the creation of a legal assembly to fail. We show that our graph-building heuristic provides relevant advantages, making it easier to obtain a connected graph with good properties with respect to the layer-based or random aggregation strategies applied in most of the optimization approaches. We also propose BRICKS, a novel dataset for the evaluation of aggregation strategies. It includes voxelizations at 3 different resolutions of 33 shapes and allows the easy comparison of different voxel aggregation strategies independently of the shape discretization step and also considering their scalability. We use it to evaluate our approach with respect to graph-based connectivity measures, showing the advantages of the proposed strategy.Item 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 StancoIn 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.