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Item Enhancing Medical Diagnosis and Treatment Planning through Automated Acquisition and Classification of Bone Fracture Patterns(The Eurographics Association, 2024) Pérez-Cano, Francisco Daniel; Parra-Cabrera, Gema; Camacho-García, Rubén; Jiménez, Juan José; Marco, Julio; Patow, GustavoThe extraction of the main features of a fractured bone area enables subsequent virtual reproduction for bone simulations. Exploring the fracture zone for other applications remains largely unexplored in current research. Recreating and analyzing fracture patterns has direct applications in medical training programs for traumatologists, automatic bone fracture reduction algorithms, and diagnostics. Furthermore, pattern classification aids in establishing treatment guidelines that specialists can follow during the surgical process. This paper focuses on the process of obtaining an accurate representation of bone fractures, starting with computed tomography scans, and subsequently classifying these patterns using a convolutional neural network. The proposed methodology aims to streamline the extraction and classification of fractures from clinical cases, contributing to enhanced diagnosis and medical simulation applications.Item Simulation of Mechanical Weathering for Modeling Rocky Terrains(The Eurographics Association, 2024) Mateos, Diego; Carranza, Luis; Susin, Anton; Argudo, Oscar; Marco, Julio; Patow, GustavoSynthetic terrains play a vital role in various applications, including entertainment, training, and simulation. This work focuses on rocky terrains akin to those found in alpine environments, which contain many complex features such as sharp ridges, loose blocks, or overhangs that are often inadequately represented by standard 2D elevation maps. We propose a novel method based on a simplified simulation of mechanical erosion processes commonly observed in high-altitude terrains, in particular the weathering due to freeze-thaw cycles. The ultimate objective is to generate plausible rocky geometry from existing 3D models, as well as account for the temporal evolution due to these weathering processes. Additionally, we have developed an artist-friendly tool integrated as an add-on into Blender.Item Adaptation of Interaction Mechanisms in Virtual Reality Shopping Environments for People with Upper Limb Motor Difficulties(The Eurographics Association, 2024) Grande, Rubén; Herrera, Vanesa; Glez-Morcillo, Carlos; Reyes, Ana de los; Castro-Schez, José J.; Albusac, Javier; Marco, Julio; Patow, Gustavo; Grande, Rubén|https://orcid.org/0000-0002-0583-6865; Herrera, Vanesa|https://orcid.org/0000-0002-6187-4794; Glez-Morcillo, Carlos|https://orcid.org/0000-0002-8568-9542; Reyes, Ana de los|https://orcid.org/0000-0003-2905-2405; Castro-Schez, José J.|https://orcid.org/0000-0002-0201-7653; Albusac, Javier|https://orcid.org/0000-0003-1889-3065In recent years, there has been research and exploration into the development of new shopping experiences within the field of electronic commerce (e-commerce). One of the technologies that can offer a more immersive shopping experience is Virtual Reality (VR). Retail giants such as Amazon and Alibaba Group have begun to use it. The technological advancement of VR, motivated by its use in various domains like e-commerce, has driven the development of software tools like APIs which allow developers to easily develop applications for these devices. One of the latest technologies included in recent VR headsets is hand tracking, which allows users to use their own hands as an input method to interact with the virtual environment. However, software tools for the development of VR applications are not fully adapted to include accessibility options for people with motor difficulties in their bodies, making it very difficult for these people to use this technology with both controllers and hand tracking. To promote accessibility options in the use of VR shopping environments, this study will present the adaptation of a set of interaction mechanisms, among which we highlight: automatic object grabbing, release of grabbed objects, navigation through the environment, attraction of distant objects, and interaction with the shopping cart. These adaptations will be made using Meta's API for Meta Quest devices as a base. The adapted environment has been tested by healthy students from the faculty and one of them with reduced mobility in the left half of his body after suffering a stroke. In this paper, we present the feedback provided by the volunteers, as well as the verification that these interaction mechanisms meet our expectations. This is an essential previous step to carry out a planned experimental session with patients with spinal cord injuries and therapist at the National Hospital for Paraplegics in Toledo (HNPT).Item Computing Manifold Next-Event Estimation without Derivatives using the Nelder-Mead Method(The Eurographics Association, 2024) Granizo-Hidalgo, Ana; Holzschuch, Nicolas; Haines, Eric; Garces, ElenaSpecular surfaces, by focusing the light that is being reflected or refracted, cause bright spots in the scene, called caustics. These caustics are challenging to compute for global illumination algorithms. Manifold-based methods (Manifold Exploration, Manifold Next-Event Estimation, Specular Next Event Estimation) compute these caustics as the zeros of an objective function, using the Newton-Raphson method. They are efficient, but require computing the derivatives of the objective function, which in turn requires local surface derivatives around the reflection point, which can be challenging to implement. In this paper, we leverage the Nelder-Mead method to compute caustics using Manifold Next-Event Estimation without having to compute local derivatives. Our method only requires local evaluations of the objective function, making it an easy addition to any path-tracing algorithm.Item Visual Navigation Support for Liver Applicator Placement using Interactive Map Displays(The Eurographics Association, 2017) Hettig, Julian; Mistelbauer, Gabriel; Rieder, Christian; Lawonn, Kai; Hansen, Christian; Stefan Bruckner and Anja Hennemuth and Bernhard Kainz and Ingrid Hotz and Dorit Merhof and Christian RiederNavigated placement of an ablation applicator in liver surgery would benefit from an effective intraoperative visualization of delicate 3D anatomical structures. In this paper, we propose an approach that facilitates surgery with an interactive as well as an animated map display to support navigated applicator placement in the liver. By reducing the visual complexity of 3D anatomical structures, we provide only the most important information on and around a planned applicator path. By employing different illustrative visualization techniques, the applicator path and its surrounding critical structures, such as blood vessels, are clearly conveyed in an unobstructed way. To retain contextual information around the applicator path and its tip, we desaturate these structures with increasing distance. To alleviate time-consuming and tedious interaction during surgery, our visualization is controlled solely by the position and orientation of a tracked applicator. This enables a direct interaction with the map display without interruption of the intervention. Based on our requirement analysis, we conducted a pilot study with eleven participants and an interactive user study with six domain experts to assess the task completion time, error rate, visual parameters and the usefulness of the animation. The outcome of our pilot study shows that our map display facilitates significantly faster decision making (11.8 s vs. 40.9 s) and significantly fewer false assessments of structures at risk (7.4 % vs. 10.3 %) compared to a currently employed 3D visualization. Furthermore, the animation supports timely perception of the course and depth of upcoming blood vessels, and helps to detect possible areas at risk along the path in advance. Hence, the obtained results demonstrate that our proposed interactive map displays exhibit potential to improve the outcome of navigated liver interventions.Item Path Sampling Methods for Differentiable Rendering(The Eurographics Association, 2024) Su, Tanli; Gkioulekas, Ioannis; Haines, Eric; Garces, ElenaWe introduce a suite of path sampling methods for differentiable rendering of scene parameters that do not induce visibility-driven discontinuities, such as BRDF parameters. We begin by deriving a path integral formulation for differentiable rendering of such parameters, which we then use to derive methods that importance sample paths according to this formulation. Our methods are analogous to path tracing and path tracing with next event estimation for primal rendering, have linear complexity, and can be implemented efficiently using path replay backpropagation. Our methods readily benefit from differential BRDF sampling routines, and can be further enhanced using multiple importance sampling and a loss-aware pixel-space adaptive sampling procedure tailored to our path integral formulation. We show experimentally that our methods reduce variance in rendered gradients by potentially orders of magnitude, and thus help accelerate inverse rendering optimization of BRDF parameters.Item Does Higher Refractive Index Mean Higher Gloss?(The Eurographics Association, 2024) Gigilashvili, Davit; Diaz Estrada, David Norman; Haines, Eric; Garces, ElenaAccording to Fresnel equations, the amount of specular reflection at the dielectric surface depends on two factors: incident angle and the difference in refractive indices of inner and outer media. Therefore, it is often assumed that the higher the refractive index of the material, the glossier it looks. However, gloss perception is a complex process that, in addition to specular reflectance, depends on many other factors, such as object's translucency and shape. In this study, we conducted two psychophysical experiments to quantify the impact of refractive index on perceived gloss for objects with varying degrees of translucency and surface roughness. For some objects a monotonic positive relationship between refractive index and perceived gloss was observed, while for others the relationship was found to be non-monotonic. Afterward, we evaluated how the refractive index affects image cues to gloss and tried to explain psychophysical results by image statistics.Item Robust Cone Step Mapping(The Eurographics Association, 2024) Bán, Róbert; Valasek, Gábor; Bálint, Csaba; Vad, Viktor A.; Haines, Eric; Garces, ElenaPer-pixel displacement mapping provides an alternative to high-fidelity geometry and flat textured faces with in-between performance costs. Although cone maps are known to facilitate efficient and robust rendering of height fields, we show that these cannot guarantee robustness under bilinear interpolation, and we propose corrections to this issue. First, we define an artifactfree minimum step size for the cone map tracing algorithm while remaining comparable in performance to that of Dummer. Second, we modify the cone map generation procedure so that at bilinearly interpolated values the unbounding cones remain disjoint from the heightmap, thereby preventing another source of rendering artifacts. Third, we introduce an exact method to generate relaxed cones such that any ray within intersects the heightmap at most once, in contrast to the original algorithm that is both computationally more expensive and generates incorrect relaxed cones. Finally, we demonstrate the applicability of these algorithm improvements with visual and performance comparisons in our C++ and HLSL implementation.Item Comparative Visualization for Diffusion Tensor Imaging Group Study at Multiple Levels of Detail(The Eurographics Association, 2017) Zhang, Changgong; Höllt, Thomas; Caan, Matthan W. A.; Eisemann, Elmar; Vilanova, Anna; Stefan Bruckner and Anja Hennemuth and Bernhard Kainz and Ingrid Hotz and Dorit Merhof and Christian RiederDiffusion Tensor Imaging (DTI) group studies often require the comparison of two groups of 3D diffusion tensor fields. The total number of datasets involved in the study and the multivariate nature of diffusion tensors together make this a challenging process. The traditional approach is to reduce the six-dimensional diffusion tensor to some scalar quantities, which can be analyzed with univariate statistical methods, and visualized with standard techniques such as slice views. However, this provides merely part of the whole story due to information reduction. If to take the full tensor information into account, only few methods are available, and they focus on the analysis of a single group, rather than the comparison of two groups. Simultaneously comparing two groups of diffusion tensor fields by simple juxtaposition or superposition is rather impractical. In this work, we extend previous work by Zhang et al. [ZCH 17] to visually compare two groups of diffusion tensor fields. To deal with the wealth of information, the comparison is carried out at multiple levels of detail. In the 3D spatial domain, we propose a detailson- demand glyph representation to support the visual comparison of the tensor ensemble summary information in a progressive manner. The spatial view guides analysts to select voxels of interest. Then at the detail level, the respective original tensor ensembles are compared in terms of tensor intrinsic properties, with special care taken to reduce visual clutter. We demonstrate the usefulness of our visual analysis system by comparing a control group and an HIV positive patient group.Item A Web-Based Tool for Cardiac Dyssynchrony Assessment on Ultrasound Data(The Eurographics Association, 2017) Pezzatini, Daniele; Yagüe, Carlos; Rudenick, Paula; Blat, Josep; Bijnens, Bart; Camara, Oscar; Stefan Bruckner and Anja Hennemuth and Bernhard Kainz and Ingrid Hotz and Dorit Merhof and Christian RiederCardiac resynchronization therapy (CRT) is a broadly used therapy in patients that suffers from heart failure (HF). The positive outcome of CRT depends strongly on the parameters criteria used to select patients and a lot of research has been done to introduce new and more reliable parameters. In this paper we propose an interactive tool to perform visual assessment and measurements on cardiac ultrasound images of patient with cardiac dyssynchrony. The tool is developed as a web application, allowing doctors to remotely access images and measurements.