17 results
Search Results
Now showing 1 - 10 of 17
Item Predictive Modeling of Material Appearance: From the Drawing Board to Interdisciplinary Applications(The Eurographics Association, 2024) Baranoski, Gladimir V. G.; Mania, Katerina; Artusi, AlessandroThis tutorial addresses one of the fundamental and timely topics of computer graphics research, namely the predictive modeling of material appearance. Although this topic is deeply rooted in traditional areas like rendering and natural phenomena simulation, this tutorial is not limited to cover contents connected to these areas. It also closely looks into the scientific methodology employed in the development of predictive models of light and matter interactions. Given the widespread use of this methodology to find modeling solutions for problems within and outside computer graphics, its discussion from a ''behind the scenes'' perspective aims to underscore practical and far-reaching aspects of interdisciplinary research that are often overlooked in related publications. More specifically, this tutorial unveils constraints and pitfalls found in each of the key stages of the model development process, namely data collection, design and evaluation, and brings forward alternatives to tackle them effectively. Furthermore, besides being a central component of realistic image synthesis frameworks, predictive material appearance models have a scope of applications that can be extended far beyond the generation of believable images. For instance, they can be employed to accelerate the hypothesis generation and validation cycles of research across a wide range of fields, from biology and medicine to photonics and remote sensing, among others. These models can also be used to generate comprehensive in silico (computational) datasets to support the translation of knowledge advances in those fields to real-world applications (e.g., the noninvasive screening of medical conditions and the remote detection of environmental hazards). In fact, a number of them are already being used in physical and life sciences, notably to support investigations seeking to strengthen the current understanding about material appearance changes prompted by mechanisms which cannot be fully studied using standard ''wet'' experimental procedures. Accordingly, such interdisciplinary research initiatives are also discussed in this tutorial through selected case studies involving the use of predictive material appearance models to elucidate challenging scientific questions.Item A Genetic Algorithm Based Heterogeneous Subsurface Scattering Representation(The Eurographics Association, 2020) Kurt, Murat; Klein, Reinhard and Rushmeier, HollyIn this paper, we present a novel heterogeneous subsurface scattering (sss) representation, which is based on a combination of Singular Value Decomposition (SVD) and genetic optimization techniques. To find the best transformation that is applied to measured subsurface scattering data, we use a genetic optimization framework, which tries various transformations to the measured heterogeneous subsurface scattering data to find the fittest one. After we apply the best transformation, we compactly represent measured subsurface scattering data by separately applying the SVD per-color channel of the transformed profiles. In order to get a compact and accurate representation, we apply the SVD on the model errors, iteratively. We validate our approach on a range of optically thick, real-world translucent materials. It's shown that our genetic algorithm based heterogeneous subsurface scattering representation achieves greater visual accuracy than alternative techniques for the same level of compression.Item A Simple Surface Tracking Method for Physically-Based 3D Water Simulations(The Eurographics Association, 2021) Amador, G.; Gomes, A.; Silva, F. and Gutierrez, D. and RodrÃguez, J. and Figueiredo, M.Water simulation, and more generically fluid simulation, is an important research topic in computer graphics. In 3D Eulerian Navier-Stokes-based water simulations, surface tracking and rendering are two delicate problems. The existing solutions to these problems (i.e., implicit surfaces-based approaches, height-fields, ray-tracing), are either to computationally intensive for real-time scenarios, or present bulge water surfaces (i.e., blobby water surfaces). In this paper, we propose a novel tracking algorithm for rendering water surfaces. Instead of tracking the flow of water using either level sets or height-fields, each cell of an 3D grid density value is directly measured in order to determine if it is either water, air, or water-air contact surface. The information in each cell is later used for the water surface splat rendering, using OpenGL vertex buffer objects.Item Procedural Modeling of Suspension Bridges(The Eurographics Association, 2021) Patow, Gustavo; Silva, F. and Gutierrez, D. and RodrÃguez, J. and Figueiredo, M.In this paper we introduce a method for designing a class of engineering structures, namely suspension bridges. These bridges are ubiquitous in the industrialized countries, often appearing in known city landscapes, yet they are complex enough that hand-based modeling is tedious and time consuming. We present a method that finds the right proportions for such a structure through an optimization method that tries to distribute the tower positions while maintaining cable width to be a finite number. By simultaneously optimizing the span and sag of the cables of a bridge, we optimize the geometry and soundness of the structure. We present the details of our technique together with examples illustrating its use, including comparisons with real structures.Item An Exploration of the Effects of in-VR Assessment Format on User Performance and Experience(The Eurographics Association, 2024) Acevedo, Pedro; Jimenez, Angela L.; Magana, Alejandra J.; Benes, Bedrich; Mousas, Christos; Hasegawa, Shoichi; Sakata, Nobuchika; Sundstedt, VeronicaFor virtual reality (VR) training and learning applications, post-intervention assessment serves as a means to validate the effectiveness of the designed practice. These assessments can occur in the virtual environment by embedding questionnaires and necessary response mechanisms. Researchers have explored embedded VR (in-VR) assessment to minimize disruption to immersion and interference with the user's sense of presence compared to 2D screen-based (out-VR) surveys. However, the influence of in-VR assessment formats on user experience and performance still needs to be explored. Therefore, we conducted a within-group study (N = 25) to compare three assessment formats on task load, usability, user experience, self-efficacy, and performance metrics (i.e., completion time, movement, and response correctness). Using an educational application focused on charged particles and electric fields, we observed no significant differences in self-reported user experience metrics across the in-VR assessment formats. However, participants achieved higher scores when interacting with the 3DStatic assessment. This preference for 3DStatic assessment highlights the advantages of 3D visualizations in VR over traditional 2D user interfaces.Item Real-Time Modelling and Rendering of Sprayed Concrete(The Eurographics Association, 2021) Vélez, G.; Matey, L.; Amundarain, A.; Ordás, F.; MarÃn, J.A.; Silva, F. and Gutierrez, D. and RodrÃguez, J. and Figueiredo, M.This paper presents a new real-time method to model and render how sprayed concrete is spread on a surface. The method not only models and renders deposits sprayed from any angle, any distance and with any concrete flow, but it is also able to compute the amount of deposited volume taking into account the percentage of material that rebounds. The proposed method has been developed for a real-time training simulator for concrete spraying machinery, where most of the algorithm is parallelised and computed in the GPU, leaving the CPU free for other computations. In this research, the method has been validated for its use on plain surfaces and tunnel walls, but it can be extended to other types of surfaces.Item MODELAR: A MODular and EvaLuative framework to improve surgical Augmented Reality visualization(The Eurographics Association, 2020) Hattab, Georges; Meyer, Felix; Albrecht, Remke Dirk; Speidel, Stefanie; Kerren, Andreas and Garth, Christoph and Marai, G. ElisabetaThe use of Augmented Reality (AR) for the visualization of 3D biomedical image data is possible thanks to a growing number of hardware and software solutions. Considerable efforts are made during surgery, where the visual information of the target structures can either be highlighted or dulled. However, as technical challenges and barriers to development decrease, it's increasingly important to take into account the specific capacities and constraints of the surgeon's perceptual and cognitive systems. To address this legitimate problem, we present a practical framework that evaluates the importance of visual encodings and renderings for surgical AR. By conducting a task-specific user study we observed a set of emerging visualization strategies. The given task is to make the kidney boundary visually salient and make the tumor and calyx distinguishable. After having recruited 23 participants, we found two preferred presets to tackle this task. With both presets, the usage of color, depth, and opacity improved the display of the organ bounds while contrasting the tumor and calyx. 19 participants successfully completed the task using MODELAR. Their preference was to either find a good preset where the organ bounds were visible then adjust the color of target objects or vice versa. MODELAR helped us better identify effective visualization that best fit the task requirements. Our evaluation results and the modular framework MODELAR is freely available and open source at https://github.com/ghattab/MODELAR.Item Directed Acyclic Graph Encoding for Compressed Shadow Maps(The Eurographics Association, 2021) Scandolo, Leonardo; Eisemann, Elmar; Binder, Nikolaus and Ritschel, TobiasDetailed shadows in large-scale environments are challenging. Our approach enables efficient detailed shadow computations for static environments at a low memory cost. It builds upon compressed precomputed multiresolution hierarchies but uses a directed acyclic graph to encode its tree structure. Further, depth values are compressed and stored separately and we use a bit-plane encoding for the lower tree levels entries in order to further reduce memory requirements and increase locality. We achieve between 20% to 50% improved compression rates, while retaining high performance.Item Efficient Propagation of Light Field Edits(The Eurographics Association, 2021) Jarabo, Adrian; Masia, Belen; Gutierrez, Diego; Silva, F. and Gutierrez, D. and RodrÃguez, J. and Figueiredo, M.Light field editing is a complex task, due to the large amount of data and the need to keep consistency between views. This has hampered the creation of efficient edit propagation methods, similar to those existing for single images. We propose a framework to edit light fields at interactive rates, by propagating some sparse user edits in the full light field. This propagation is guided by a novel affinity function, which forces similar pixels (defined by our affinity space) to receive similar edits, thus ensuring consistency. To manage the light field's large amount of data, we propose a novel multi-dimensional downsampling technique: we first cluster pixels with high affinity, and then perform edit propagation over the downsampled data. We finally upsample back to the original full resolution, maintaining visual fidelity and view consistency between views.Item Augmented Reality for Web - A New Interaction Method Without Markers(The Eurographics Association, 2021) Silva, Luis F. A.; Silva, Frutuoso G. M.; Silva, F. and Gutierrez, D. and RodrÃguez, J. and Figueiredo, M.In the new age of omnipresent internet, browsers are accessible on every device in everyday's life. Thus it is also needed new interaction methods to facilitate the interaction through browser. Augmented reality is one of the techniques that is available now via browser. In this paper we present a new method of interaction without physical markers for augmented reality via browser. The first part of the paper describes the use of augmented reality via browser using physical markers and its limitations. In the second part, we propose a solution to solve the limitations of augmented reality using physical markers, i.e. we propose a new interaction method to manipulate virtual objects without using physical markers. Finally, we show a simple augmented web game based on the new interaction method proposed.