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Item 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 StancoContinuous 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.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 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 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.Item Gradient Field Estimation on Triangle Meshes(The Eurographics Association, 2018) Mancinelli, C.; Livesu, M.; Puppo, E.; Livesu, Marco and Pintore, Gianni and Signoroni, AlbertoThe 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.