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Item SynthPS: a Benchmark for Evaluation of Photometric Stereo Algorithms for Cultural Heritage Applications(The Eurographics Association, 2020) Dulecha, Tinsae Gebrechristos; Pintus, Ruggero; Gobbetti, Enrico; Giachetti, Andrea; Spagnuolo, Michela and Melero, Francisco JavierPhotometric Stereo (PS) is a technique for estimating surface normals from a collection of images captured from a fixed viewpoint and with variable lighting. Over the years, several methods have been proposed for the task, trying to cope with different materials, lights, and camera calibration issues. An accurate evaluation and selection of the best PS methods for different materials and acquisition setups is a fundamental step for the accurate quantitative reconstruction of objects' shapes. In particular, it would boost quantitative reconstruction in the Cultural Heritage domain, where a large amount of Multi-Light Image Collections are captured with light domes or handheld Reflectance Transformation Imaging protocols. However, the lack of benchmarks specifically designed for this goal makes it difficult to compare the available methods and choose the most suitable technique for practical applications. An ideal benchmark should enable the evaluation of the quality of the reconstructed normals on the kind of surfaces typically captured in real-world applications, possibly evaluating performance variability as a function of material properties, light distribution, and image quality. The evaluation should not depend on light and camera calibration issues. In this paper, we propose a benchmark of this kind, SynthPS, which includes synthetic, physically-based renderings of Cultural Heritage object models with different assigned materials. SynthPS allowed us to evaluate the performance of classical, robust and learning-based Photometric Stereo approaches on different materials with different light distributions, also analyzing their robustness against errors typically arising in practical acquisition settings, including robustness against gamma correction and light calibration errors.Item A Comparison of Navigation Techniques in a Virtual Museum Scenario(The Eurographics Association, 2019) Caputo,Ariel; Borin, Federico; Giachetti, Andrea; Rizvic, Selma and Rodriguez Echavarria, KarinaThanks to the recent availability of low-cost immersive Virtual Reality (VR) devices, applications like Virtual Museums, where the users can explore fictional or recreated buildings hosting different artworks, are becoming increasingly popular. Different solutions can be implemented to enable users' navigation in an immersive Virtual Museum and the choice of the best one for a specific application is not easy, as several issues must be taken into account, like motion sickness, user's freedom, loss of orientation. In this work, we propose a novel locomotion technique called Map Overview Teleport, particularly suitable for exploration of virtual museums and compare it with standard ones in a specifically designed user study. The outcomes of the experiment give useful insights into the design of effective applications.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 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 Aging Prediction of Cultural Heritage Samples Based on Surface Microgeometry(The Eurographics Association, 2018) Ciortan, Irina Mihaela; Marchioro, Giacomo; Daffara, Claudia; Pintus, Ruggero; Gobbetti, Enrico; Giachetti, Andrea; Sablatnig, Robert and Wimmer, MichaelA critical and challenging aspect for the study of Cultural Heritage (CH) assets is related to the characterization of the materials that compose them and to the variation of these materials with time. In this paper, we exploit a realistic dataset of artificially aged metallic samples treated with different coatings commonly used for artworks' protection in order to evaluate different approaches to extract material features from high-resolution depth maps. In particular, we estimated, on microprofilometric surface acquisitions of the samples, performed at different aging steps, standard roughness descriptors used in materials science as well as classical and recent image texture descriptors. We analyzed the ability of the features to discriminate different aging steps and performed supervised classification tests showing the feasibility of a texture-based aging analysis and the effectiveness of coatings in reducing the surfaces' change with time.Item Objective and Subjective Evaluation of Virtual Relighting from Reflectance Transformation Imaging Data(The Eurographics Association, 2018) Pintus, Ruggero; Dulecha, Tinsae; Jaspe, Alberto; Giachetti, Andrea; Ciortan, Irina; Gobbetti, Enrico; Sablatnig, Robert and Wimmer, MichaelReflectance Transformation Imaging (RTI) is widely used to produce relightable models from multi-light image collections. These models are used for a variety of tasks in the Cultural Heritage field. In this work, we carry out an objective and subjective evaluation of RTI data visualization. We start from the acquisition of a series of objects with different geometry and appearance characteristics using a common dome-based configuration. We then transform the acquired data into relightable representations using different approaches: PTM, HSH, and RBF. We then perform an objective error estimation by comparing ground truth images with relighted ones in a leave-one-out framework using PSNR and SSIM error metrics. Moreover, we carry out a subjective investigation through perceptual experiments involving end users with a variety of backgrounds. Objective and subjective tests are shown to behave consistently, and significant differences are found between the various methods. While the proposed analysis has been performed on three common and state-of-the-art RTI visualization methods, our approach is general enough to be extended and applied in the future to new developed multi-light processing pipelines and rendering solutions, to assess their numerical precision and accuracy, and their perceptual visual quality.Item Web-based Multi-layered Exploration of Annotated Image-based Shape and Material Models(The Eurographics Association, 2019) Villanueva, Alberto Jaspe; Pintus, Ruggero; Giachetti, Andrea; Gobbetti, Enrico; Rizvic, Selma and Rodriguez Echavarria, KarinaWe introduce a novel versatile approach for letting users explore detailed image-based shape and material models integrated with structured, spatially-associated descriptive information. We represent the objects of interest as a series of registered layers of image-based shape and material information. These layers are represented at multiple scales, and can come out of a variety of pipelines and include both RTI representations and spatially-varying normal and BRDF fields, eventually as a result of fusing multi-spectral data. An overlay image pyramid associates visual annotations to the various scales. The overlay pyramid of each layer can be easily authored at data preparation time using widely available image editing tools. At run-time, an annotated multi-layered dataset is made available to clients by a standard web server. Users can explore these datasets on a variety of devices, from mobile phones to large scale displays in museum installations, using JavaScript/WebGL2 clients capable to perform layer selection, interactive relighting and enhanced visualization, annotation display, and focus-and-context multiple-layer exploration using a lens metaphor. The capabilities of our approach are demonstrated on a variety of cultural heritage use cases involving different kinds of annotated surface and material models.Item EUROGRAPHICS 2019: CGF 38-2 STARs Frontmatter(The Eurographics Association and John Wiley & Sons Ltd., 2019) Giachetti, Andrea; Rushmeyer, Holly; Giachetti, Andrea and Rushmeyer, Holly-Item FloralSurf: Space-Filling Geodesic Ornaments(The Eurographics Association, 2023) Albano, Valerio; Fanni, Filippo Andrea; Giachetti, Andrea; Pellacini, Fabio; Ritschel, Tobias; Weidlich, AndreaWe propose a method to generate floral patterns on manifolds without relying on parametrizations. Taking inspiration from the literature on procedural space-filling vegetation, these patterns are made of non-intersecting ornaments that are grown on the surface by repeatedly adding different types of decorative elements, until the whole surface is covered. Each decorative element is defined by a set of geodesic Bézier splines and a set of growth points from which to continue growing the ornaments. Ornaments are grown in a greedy fashion, one decorative element at a time. At each step, we analyze a set of candidates, and retain the one that maximizes surface coverage, while ensuring that it does not intersect other ornaments. All operations in our method are performed in the intrinsic metric of the surface, thus ensuring that the derived decorations have good coverage, with neither distortions nor discontinuities, and can be grown on complex surfaces. In our method, users control the decorations by selecting the size and shape of the decorative elements and the position of the growth points.We demonstrate decorations that vary in the length of the ornaments' lines, and the number, scale and orientation of the placed decorations. We show that these patterns mimic closely the design of hand-drawn objects. Our algorithm supports any manifold surface represented as triangle meshes. In particular, we demonstrate patterns generated on surfaces with high genus, with and without borders and holes, and that can include a mixture of thin and large features.Item SHREC 2020 Track: River Gravel Characterization(The Eurographics Association, 2020) Giachetti, Andrea; Biasotti, Silvia; Moscoso Thompson, Elia; Fraccarollo, Luigi; Nguyen, Quang; Nguyen, Hai-Dang; Tran, Minh-Triet; Arvanitis, Gerasimos; Romanelis, Ioannis; Fotis, Vlasis; Moustakas, Konstantinos; Tortorici, Claudio; Werghi, Naoufel; Berretti, Stefano; Schreck, Tobias and Theoharis, Theoharis and Pratikakis, Ioannis and Spagnuolo, Michela and Veltkamp, Remco C.The quantitative analysis of the distribution of the different types of sands, gravels and cobbles shaping river beds is a very important task performed by hydrologists to derive useful information on fluvial dynamics and related processes (e.g., hydraulic resistance, sediment transport and erosion, habitat suitability. As the methods currently employed in the practice to perform this evaluation are expensive and time-consuming, the development of fast and accurate methods able to provide a reasonable estimate of the gravel distribution based on images or 3D scanning data would be extremely useful to support hydrologists in their work. To evaluate the suitability of state-of-the-art geometry processing tool to estimate the distribution from digital surface data, we created, therefore, a dataset including real captures of riverbed mockups, designed a retrieval task on it and proposed them as a challenge of the 3D Shape Retrieval Contest (SHREC) 2020. In this paper, we discuss the results obtained by the methods proposed by the groups participating in the contest and baseline methods provided by the organizers. Retrieval methods have been compared using the precision-recall curves, nearest neighbor, first tier, second tier, normalized discounted cumulated gain and average dynamic recall. Results show the feasibility of gravels characterization from captured surfaces and issues in the discrimination of mixture of gravels of different size.