Browsing by Author "Andujar, Carlos"
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Item An Annotation Tool for Digital Restoration of Wall Paintings(The Eurographics Association, 2022) Barreiro Díaz, Albert; Munoz-Pandiella, Imanol; Bosch, Carles; Andujar, Carlos; Ponchio, Federico; Pintus, RuggeroAntique paintings are essential to study and understand our past. Paintings, and specifically mural paintings, are delicate artworks that are affected by multiple deterioration conditions. Weathering and human interventions cause different damage problems, and physical and chemical changes degrade their visual color appearance. As a consequence, art historians and archaeologists require a huge effort to attempt to rebuild their original appearance. The annotation of digital images of the paintings is a valuable tool in this process. In this paper we analyze major requirements from art historians concerning the annotation of painting regions from the point of view of digital restoration. We also describe a tool prototype (based on TagLab) intended to facilitate the annotation and segmentation of mural paintings. The tool assists art historians in formulating multiple hypotheses on the original appearance by supporting multiple annotation layers for degradation and color, providing both hand-drawn and semi-automatic segmentation, and offering web-based dissemination and sharing of the annotations through the W3C Web Annotation Data Model.Item Combining Motion Matching and Orientation Prediction to Animate Avatars for Consumer-Grade VR Devices(The Eurographics Association and John Wiley & Sons Ltd., 2022) Ponton, Jose Luis; Yun, Haoran; Andujar, Carlos; Pelechano, Nuria; Dominik L. Michels; Soeren PirkThe animation of user avatars plays a crucial role in conveying their pose, gestures, and relative distances to virtual objects or other users. Self-avatar animation in immersive VR helps improve the user experience and provides a Sense of Embodiment. However, consumer-grade VR devices typically include at most three trackers, one at the Head Mounted Display (HMD), and two at the handheld VR controllers. Since the problem of reconstructing the user pose from such sparse data is ill-defined, especially for the lower body, the approach adopted by most VR games consists of assuming the body orientation matches that of the HMD, and applying animation blending and time-warping from a reduced set of animations. Unfortunately, this approach produces noticeable mismatches between user and avatar movements. In this work we present a new approach to animate user avatars that is suitable for current mainstream VR devices. First, we use a neural network to estimate the user's body orientation based on the tracking information from the HMD and the hand controllers. Then we use this orientation together with the velocity and rotation of the HMD to build a feature vector that feeds a Motion Matching algorithm. We built a MoCap database with animations of VR users wearing a HMD and used it to test our approach on both self-avatars and other users' avatars. Our results show that our system can provide a large variety of lower body animations while correctly matching the user orientation, which in turn allows us to represent not only forward movements but also stepping in any direction.Item Digital Layered Models of Architecture and Mural Paintings over Time(The Eurographics Association, 2021) Guardia, Milagros; Pogliani, Paola; Bordi, Giulia; Charalambous, Panayiotis; Andujar, Carlos; Munoz-Pandiella, Imanol; Pueyo, Xavier; Ortega, Lidia M. and Chica, AntonioThe European project Enhancement of Heritage Experiences: The Middle Ages. Digital Layered Models of Architecture and Mural Paintings over Time (EHEM) aims to obtain virtual reconstructions of medieval artistic heritage -architecture with mural paintings- that are as close as possible to the original at different times, incorporating historical-artistic knowledge and the diachronic perspective of heritage. The project has also the purpose of incorporating not only how these painted buildings are and how they were, but also what function they had, how they were used and how they were perceived by the different users. EHEM will offer an instrument for researchers, restorers and heritage curators and will “humanize” the heritage proposing to the spectator of the 21st century an experience close to the users of the Middle Ages.Item Digital Layered Models of Architecture and Mural Paintings over Time(The Eurographics Association, 2020) Guardia, Milagros; Pogliani, Paola; Bordi, Giulia; Charalambous, Panayiotis; Andujar, Carlos; Pueyo, Xavier; Spagnuolo, Michela and Melero, Francisco JavierThe European project Enhancement of Heritage Experiences: The Middle Ages. Digital Layered Models of Architecture and Mural Paintings over Time (EHEM), approved in the call for JPICH Conservation, Protection and Use (0127) in the year 2020, aims to obtain virtual reconstructions of medieval artistic heritage - architecture with mural paintings - that are as close as possible to the original at different times, incorporating historical-artistic knowledge and the diachronic perspective of heritage, as an instrument for researchers, restorers and heritage curators and to improve the visitor's perceptions and experiences. In the digital models elaborated we intend to develop, as concrete objectives: 1. The understanding of architectural complexity, which is usually regularized geometrically. 2. Solving chromatic problems. The analysis of pigments, the arrangement of the pictorial layers and the successive restorations suffered, with the help of conservation and restoration technicians, will allow us to digitally specify the original colouring of the paintings. 3. Raise and propose the resolution of lighting problems. To date, trials have been carried out for the restitution of these problems in digital models based on the analysis of natural lighting, which we intend to improve. We also propose to deal with artificial lighting by chandeliers or oil lamps, which produced effects of painting vibration at the moment when, for liturgical reasons, the images ''acted''. 4. To approach digitally the different perspectives of the medieval building and its paintings according to the categories of users. To this end we have chosen three sites that because of their complexity will serve as case studies: The early medieval church of Santa Maria Antiqua in Rome (Italy), a mural palimpsest, consisting of up to ten layers of overlapping painted plasters, realised during a relatively short period of life (sixth-ninth centuries), which also poses architectural challenges of visual resolution given that it was transformed into a church from the Domitianic entrance hall in the Roman Forum to the imperial Palace on the Palatine hill. The hermitage of Sant Quirze de Pedret (Spain), with its complex architectural genesis from the tenth century, was decorated at the head of the church at two different times by superimposing a layer on the previous one. The discovery of its paintings, their removal and the transfer to two museums took place at two different moments (1921 and 1937) and with very different procedures. At the same time, years later, radical interventions were made to the building, altering the two pictorial phases in its ''virtual'' presentation. The Engleistra or Place of Seclusion founded by Neophytos (Agios Neophytos Monastery, Cyprus) The oratory was excavated in the rock from a natural cave and was decorated, at different times during the Middle Ages, with Byzantine wall paintings. The extreme nature of the site and the irregular nature of the rocky surface that house these cycles, comprising of up to five phases constitute a fundamental challenge for their digital presentation.Item Digital Reintegration of Distributed Mural Paintings at Different Architectural Phases: the Case of St. Quirze de Pedret(The Eurographics Association, 2022) Munoz-Pandiella, Imanol; Argudo, Oscar; Otzet, Immaculada Lorés; Comas, Joan Font; Casademont, Genís Àvila; Pueyo, Xavier; Andujar, Carlos; Ponchio, Federico; Pintus, RuggeroSant Quirze de Pedret is a Romanesque church located in Cercs (Catalonia, Spain) at the foothills of the Pyrenees. Its walls harbored one of the most important examples of mural paintings in Catalan Romanesque Art. However, in two different campaigns (in 1921 and 1937) the paintings were removed using the strappo technique and transferred to museums for safekeeping. This detachment protected the paintings from being sold in the art market, but at the price of breaking the integrity of the monument. Nowadays, the paintings are exhibited in the Museu Nacional d'Art de Catalunya - MNAC (Barcelona, Catalonia) and the Museu Diocesà i Comarcal de Solsona - MDCS (Solsona, Catalonia). Some fragments of the paintings are still on the walls of the church. In this work, we present the methodology to digitally reconstruct the church building at its different phases and group the dispersed paintings in a single virtual church, commissioned by the MDCS. We have combined 3D reconstruction (LIDAR and photogrammetric using portable artificial illumination) and modeling techniques (including texture transfer between different shapes) to recover the integrity of the monument in a single 3D virtual model. Furthermore, we have reconstructed the church building at different significant historical moments and placed actual paintings on its virtual walls, based on archaeological knowledge. This set of 3D models allows experts and visitors to better understand the monument as a whole, the relations between the different paintings, and its evolution over time.Item Easy Authoring of Image-Supported Short Stories for 3D Scanned Cultural Heritage(The Eurographics Association, 2020) Comino Trinidad, Marc; Chica, Antoni; Andujar, Carlos; Spagnuolo, Michela and Melero, Francisco JavierVisual storytelling is a powerful tool for Cultural Heritage communication. However, traditional authoring tools either produce videos that cannot be fully integrated with 3D scanned models, or require 3D content creation skills that imply a high entry barrier for Cultural Heritage experts. In this paper we present an image-supported, video-based authoring tool allowing non- 3D-experts to create rich narrative content that can be fully integrated in immersive virtual reality experiences. Given an existing 3D scanned model, each story is based on a user-provided photo or system-proposed image. First, the system automatically registers the image against the 3D model, and creates an undistorted version that will serve as a fixed background image for the story. Authors can then use their favorite presentation software to annotate or edit the image while recording their voice. The resulting video is processed automatically to detect per-frame regions-of-interest. At visualization time, videos are projected onto the 3D scanned model, allowing the audience to watch the narrative piece in its surrounding spatial context. We discuss multiple color blending techniques, inspired by detail textures, to provide high-resolution detail. The system uses the image-to-model registration data to find suitable locations for triggers and avatars that draw the user attention towards the 3D model parts being referred to by the presenter. We conducted an informal user study to evaluate the quality of the immersive experience. Our findings suggest that our approach is a valuable tool for fast and easy creation of fully-immersive visual storytelling experiences.Item Effective Visualization of Sparse Image-to-Image Correspondences(The Eurographics Association, 2020) Andujar, Carlos; Chica, Antonio; Comino Trinidad, Marc; Kerren, Andreas and Garth, Christoph and Marai, G. ElisabetaFinding robust correspondences between images is a crucial step in photogrammetry applications. The traditional approach to visualize sparse matches between two images is to place them side-by-side and draw link segments connecting pixels with matching features. In this paper we present new visualization techniques for sparse correspondences between image pairs. Key ingredients of our techniques include (a) the clustering of consistent matches, (b) the optimization of the image layout to minimize occlusions due to the super-imposed links, (c) a color mapping to minimize color interference among links (d) a criterion for giving visibility priority to isolated links, (e) the bending of link segments to put apart nearby links, and (f) the use of glyphs to facilitate the identification of matching keypoints. We show that our technique substantially reduces the clutter in the final composite image and thus makes it easier to detect and inspect both inlier and outlier matches. Potential applications include the validation of image pairs in difficult setups and the visual comparison of feature detection / matching algorithms.Item Immersive Geometry-based and Image-based Exploration of Cultural Heritage Models(The Eurographics Association, 2021) Farràs, Arnau; Comino Trinidad, Marc; Andujar, Carlos; Hulusic, Vedad and Chalmers, AlanRecent advances in 3D acquisition technologies have facilitated the inexpensive digitization of cultural heritage. In addition to the 3D digital model, in many cases multiple photo collections are also available. These photo collections often provide valuable information not included in the 3D digital model. In this paper we describe a VR-ready web application to simultaneously explore a cultural heritage model together with arbitrary photo collections. At any time, users can define a region of interest either explicitly or implicitly, and the application retrieves, scores, groups and shows a matching subset of the photos. Users can then select a photo to project it onto the 3D model, to inspect the photo separately, or to teleport to the position the photo was taken from. Unlike previous approaches for joint 2D-3D model exploration, our interface has been specifically adapted to VR. We conducted a user study and found that the application greatly facilitates navigation and provides a fast, intuitive access to the available photos. The application supports any modern browser running on desktop, mobile and VR headset systems.Item Neural Colorization of Laser Scans(The Eurographics Association, 2021) Comino Trinidad, Marc; Andujar, Carlos; Bosch, Carles; Chica, Antonio; Muñoz-Pandiella, Imanol; Ortega, Lidia M. and Chica, AntonioLaser scanners enable the digitization of 3D surfaces by generating a point cloud where each point sample includes an intensity (infrared reflectivity) value. Some LiDAR scanners also incorporate cameras to capture the color of the surfaces visible from the scanner location. Getting usable colors everywhere across 360° scans is a challenging task, especially for indoor scenes. LiDAR scanners lack flashes, and placing proper light sources for a 360° indoor scene is either unfeasible or undesirable. As a result, color data from LiDAR scans often do not have an adequate quality, either because of poor exposition (too bright or too dark areas) or because of severe illumination changes between scans (e.g. direct Sunlight vs cloudy lighting). In this paper, we present a new method to recover plausible color data from the infrared data available in LiDAR scans. The main idea is to train an adapted image-to-image translation network using color and intensity values on well-exposed areas of scans. At inference time, the network is able to recover plausible color using exclusively the intensity values. The immediate application of our approach is the selective colorization of LiDAR data in those scans or regions with missing or poor color data.Item A Parser-based Tool to Assist Instructors in Grading Computer Graphics Assignments(The Eurographics Association, 2019) Andujar, Carlos; Raluca Vijulie, Cristina; Vinacua, Alvar; Tarini, Marco and Galin, EricAlthough online e-learning environments are increasingly used in university courses, manual assessment still dominates the way students are graded. Interactive judges providing a pass/fail verdict based on test sets are valuable tools both for learning and assessment, but still rely on human review of the code for output-independent issues such as readability and efficiency. In this paper we present a tool to assist instructors in grading programming exercises in Computer Graphics (CG) courses. In contrast to other grading solutions, assessment is based both on checking the output against test sets, and through a set of instructor-defined rubrics based on syntax analysis of the source code. Our current prototype runs in Python and supports the assessment of shaders written in GLSL language. We tested the tool in a CG course involving more than one hundred Computer Science students per year. Our first experiments show the tool can be useful to support both self-assessment and grading, as well as detecting grading mistakes through anomaly detection techniques based on features extracted from the syntax analysis.Item Radiance-Based Blender Add-On for Physically Accurate Rendering of Cultural Heritage(The Eurographics Association, 2023) Méndez, Míriam; Munoz-Pandiella, Imanol; Andujar, Carlos; Singh, Gurprit; Chu, Mengyu (Rachel)Despite the Cultural Heritage and Computer Graphics communities are increasingly joining forces to strengthen their collaboration, the study of how light interacts with monuments (e.g. weathering the surfaces or affecting the visitors' experience) is still an open problem in cultural heritage. A significant limitation is the lack of easy-to-use, open-source, physically-accurate tools allowing cultural heritage experts to perform lighting simulations on the increasing collection of 3D reconstructions. In this work, we present an open-source Blender add-on to facilitate such simulations. The add-on allows art historians to configure the properties (materials, lights, and camera) of the simulation, and uses as rendering back-end the Radiance software, a validated physically accurate light simulation tool. Our tool lowers the entry barrier for the use of a highly accurate but rather complex (command-based) tool for lighting studies in cultural heritage monuments.Item A Tool for N-way Analysis of Programming Exercises(The Eurographics Association, 2020) Andujar, Carlos; Comino Trinidad, Marc; Fairén, Marta; Vinacua, Àlvar; Byška, Jan and Jänicke, StefanAbstract Programming exercises are a corner stone in Computer Science courses. If used properly, these exercises provide valuable feedback both to students and instructors. Unfortunately, the assessment of student submissions through code inspection requires a considerable amount of time. In this work we present an interactive tool to support the analysis of code submissions before, during, and after grading. The key idea is to compute a dissimilarity matrix for code submissions, using a metric that incorporates syntactic, semantic and functional aspects of the code. This matrix is used to embed the submissions in 2D space, so that similar submissions are mapped to nearby locations. The tool allows users to visually identify clusters, inspect individual submissions, and perform detailed pair-wise and abridged n-way comparisons. Finally, our approach facilitates comparative scoring by presenting submissions in a nearly-optimal order, i.e. similar submissions appear close in the sequence. Our initial evaluation indicates that the tool (currently supporting C++/GLSL code) provides clear benefits both to students (more fair scores, less bias, more consistent feedback) and instructors (less effort, better feedback on student performance).Item A Virtual Reality Front-end for City Modeling(The Eurographics Association, 2019) Rando, Eduard; Andujar, Carlos; Patow, Gustavo A.; Casas, Dan and Jarabo, AdriánCurrent tools for city modeling, including those supporting procedural techniques, have a steep learning curve and require substantial user input and/or skills to create realistic 3D models of cities. In this paper we propose a VR tool for the fast and intuitive creation of 3D models of cities through their main elements (buildings, blocks and streets). The key ingredients of our approach are: (a) intuitive creation of mass volume models for buildings, whose facades can be refined later on through procedural rules, (b) the ability to use arbitrary urban layouts, either created from scratch within the tool or imported from public map services, (c) algorithms to replicate and transfer user-generated blocks to arbitrary block shapes, so that a few template blocks suffice to cover the whole urban layout. The major benefit of our approach is that city design and inspection tasks are done simultaneously in a completely immersive environment.Item VR-assisted Architectural Design in a Heritage Site: the Sagrada Família Case Study(The Eurographics Association, 2018) Andujar, Carlos; Brunet, Pere; Buxareu, Jerónimo; Fons, Joan; Laguarda, Narcís; Pascual, Jordi; Pelechano, Nuria; Sablatnig, Robert and Wimmer, MichaelVirtual Reality (VR) simulations have long been proposed to allow users to explore both yet-to-built buildings in architectural design, and ancient, remote or disappeared buildings in cultural heritage. In this paper we describe an on-going VR project on an UNESCO World Heritage Site that simultaneously addresses both scenarios: supporting architects in the task of designing the remaining parts of a large unfinished building, and simulating existing parts that define the environment that new designs must conform to. The main challenge for the team of architects is to advance towards the project completion being faithful to the original Gaudí's project, since many plans, drawings and plaster models were lost. We analyze the main requirements for collaborative architectural design in such a unique scenario, describe the main technical challenges, and discuss the lessons learned after one year of use of the system.