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Item Real-Time Rendering of Molecular Dynamics Simulation Data: A Tutorial(The Eurographics Association, 2017) Alharbi, Naif; Chavent, Matthieu; Laramee, Robert S.; Tao Ruan Wan and Franck VidalAchieving real-time molecular dynamics rendering is a challenge, especially when the rendering requires intensive computation involving a large simulation data-set. The task becomes even more challenging when the size of the data is too large to fit into random access memory (RAM) and the final imagery depends on the input and output (I/O) performance. The large data size and the complex computation processing per frame pose a number of challenges. i.e. the I/O performance bottleneck, the computational processing performance costs, and the fast rendering challenge. Handling these challenges separately consumes a significant portion of the total processing time which may result in low frame rates. We address these challenges by proposing an approach utilizing advanced memory management and bridging the Open Computing Language (OpenCL) and Open Graphics Library (OpenGL) drivers to optimize the final rendering frame rate. We illustrate the concept of the memory mapping technique and the hybrid OpenCL and OpenGL combination through a real molecular dynamics simulation example. The simulation data-set specifies the evolution of 336,260 particles over 1981 time steps occupying 8 Gigabyte of memory. The dynamics of the system including the lipid-protein interactions can be rendered at up to 40 FPS.Item Selective Rasterized Ray-traced Reflections on the GPU(The Eurographics Association, 2016) Kastrati, Mattias Frid; Goswami, Prashant; Giovanni Pintore and Filippo StancoRay-tracing achieves impressive effects such as realistic reflections on complex surfaces but is also more computationally expensive than classic rasterization. Rasterized ray-tracing methods can accelerate ray-tracing by taking advantage of the massive parallelization available in the rasterization pipeline on the GPU. In this paper, we propose a selective rasterized raytracing method that optimizes the rasterized ray-tracing by selectively allocating computational resources to reflective regions in the image. Our experiments suggest that the method can speed-up the computation by up to 4 times and also reduce the memory footprint by almost 66% without affecting the image quality. We demonstrate the effectiveness of our method using complex scenes and animations.Item Surfel Octrees: A New Scheme for Interactive Inspection of Anatomy Atlases in Client-Server Applications(The Eurographics Association, 2015) Surinyac, Jordi; Brunet, Pere; Mateu Sbert and Jorge Lopez-MorenoNowadays, an increasing interest on tele-medicine and tele-diagnostic solutions can be observed, with client/server architectures for remote inspection of volume image-based medical data which are becoming more and more popular. The use of portable devices is gradually spreading due to their portability and easy maintenance. In this paper, we present an efficient data model for segmented volume models based on a hierarchical data structure of surfels per anatomical structure. Surfel Octrees are compact enough for transmission through networks with limited bandwidth, and provide good visual quality in the client devices at a limited footprint. Anatomy atlases are represented as octree forests, supporting local interaction in the client device and selection of groups of medical organs. After presenting the octree generation and interaction algorithms, we present several examples and discuss the interest of the proposed approach in low-end devices such as mobiles and tablets.Item ViewFusion: Correlating Structure and Activity Views for Execution Traces(The Eurographics Association, 2012) Trümper, Jonas; Telea, Alexandru; Döllner, Jürgen; Hamish Carr and Silvester CzannerVisualization of data on structure and related temporal activity supports the analysis of correlations between the two types of data. This is typically done by linked views. This has shortcomings with respect to efficient space usage and makes mapping the effect of user input into one view into the other view difficult. We propose here a novel, space-efficient technique that 'fuses' the two information spaces - structure and activity - in one view. We base our technique on the idea that user interaction should be simple, yet easy to understand and follow. We apply our technique, implemented in a prototype tool, for the understanding of software engineering datasets, namely static structure and execution traces of the Chromium web browser.Item GPU Visualization and Voxelization of Yarn-Level Cloth(The Eurographics Association, 2014) Lopez-Moreno, Jorge; Cirio, Gabriel; Miraut, David; Otaduy, Miguel Angel; Adolfo Munoz and Pere-Pau VazquezMost popular methods in cloth rendering rely on volumetric data in order to model complex optical phenomena such as sub-surface scattering. Previous work represents yarns as a sequence of identical but rotated crosssections. While these approaches are able to produce very realistic illumination models, the required volumetric representation is difficult to compute and render, forfeiting any interactive feedback. In this paper, we introduce a method based on the GPU for simultaneous visualization and voxelization, suitable for both interactive and offline rendering. Our method can interactively voxelize millions of polygons into a 3D texture, generating a volume with sub-voxel accuracy which is suitable even for high-density weaving such as linen.Item From the Patient to the Surgery - A Complete Computer Vision and Graphics Process(The Eurographics Association, 2012) Martinez, A.; Jimenez, J.; Isabel Navazo and Gustavo PatowGenerating digital information ready to use on a surgery operation from a patient is a complex process. This process involves computer vision techniques, in order to extract digital information from medical images, and computer graphics techniques in order to generate proper models to interact with the digital information. In this approach a set of techniques covering both fields (computer vision and graphics) have been used to develop a complete process from the medical image to the surgery training.Item Downsampling and Storage of Pre-Computed Gradients for Volume Rendering(The Eurographics Association, 2017) DÃaz-GarcÃa, Jesús; Brunet, Pere; Navazo, Isabel; Vázquez, Pere-Pau; Fco. Javier Melero and Nuria PelechanoThe way in which gradients are computed in volume datasets influences both the quality of the shading and the performance obtained in rendering algorithms. In particular, the visualization of coarse datasets in multi-resolution representations is affected when gradients are evaluated on-the-fly in the shader code by accessing neighbouring positions. This is not only a costly computation that compromises the performance of the visualization process, but also one that provides gradients of low quality that do not resemble the originals as much as desired because of the new topology of downsampled datasets. An obvious solution is to pre-compute the gradients and store them. Unfortunately, this originates two problems: First, the downsampling process, that is also prone to generate artifacts. Second, the limited bit size of storage itself causes the gradients to loss precision. In order to solve these issues, we propose a downsampling filter for pre-computed gradients that provides improved gradients that better match the originals such that the aforementioned artifacts disappear. Secondly, to address the storage problem, we present a method for the efficient storage of gradient directions that is able to minimize the minimum angle achieved among all representable vectors in a space of 3 bytes. We also provide several examples that show the advantages of the proposed approaches.Item Multi-Perspective Detail+Overview Visualization for 3D Building Exploration(The Eurographics Association, 2013) Pasewaldt, Sebastian; Trapp, Matthias; Döllner, Jürgen; Silvester Czanner and Wen TangVirtual 3D building models, as key elements of virtual 3D city models, are used in a growing number of application domains, such as geoanalysis, disaster management and architectural planning. Visualization systems for such building models often rely on perspective or orthogonal projections using a single viewpoint. Therefore, the exploration of a complete model requires a user to change the viewpoint multiple times and to memorize the content of each view to obtain a comprehensive mental model. Since this is usually a time-consuming task, which implies context switching, current visualization systems use multiple viewports to simultaneously depict an object from different perspectives. Our approach extends the idea of multiple viewports by combining two linked views for the interactive exploration of virtual 3D buildings model and their façades. In contrast to traditional approaches, we automatically generate a multi-perspective view that simultaneously depicts all façades of the building in one overview image. This facilitates the process of obtaining overviews and supports fast and direct navigation to various points-of-interest. We describe the concept and implementations of our Multiple-Center-of-Projection camera model for real-time multi-perspective image synthesis. Further, we provide insights into different interaction techniques for linked multi-perspective views and outline approaches of future work.Item A New Approach for Perceptually-based Fitting Strokes into Straight Segments(The Eurographics Association, 2015) Plumed, Raquel; Company, Pedro; Varley, Peter A. C.; Mateu Sbert and Jorge Lopez-MorenoFitting the strokes of a sketch into geometrical primitives is still an open problem, even for sketches which depict bare line-drawings without annotations. Such sketches comprise only discrete strokes, sequences of points obtained between a pen down and a pen up. It is commonly accepted that the best perceptual fittings depend on the context. Hence, we will only be able to extract the best line-drawing from a sketch by considering a complex recognition flow, where lines must be iteratively fitted according to different tentative relationships until the most plausible line-drawing is reached. The recognition task considered in this paper is determining whether a stroke represents a straight line. The goal is doing it in a way that allows for iterative recognition flows. The novel contributions are that our approach is more fast and robust than accurate, uses perceptual criteria to classify strokes, and returns likeliness instead of a simple yes/no.Item Image-Based Flow Transfer(The Eurographics Association, 2014) Bosch, Carles; Patow, Gustavo A.; Adolfo Munoz and Pere-Pau VazquezWeathering phenomena are ubiquitous to urban environments. In particular, fluid flow becomes a specially representative but difficult phenomenon to reproduce. In order to produce realistic flow effects, it is possible to take advantage of the widespread availability of flow images on the internet, which can be used to gather key information about the flow. In this paper we present a technique that allows transferring flow phenomena between photographs, adapting the flow to the target image and giving the user flexibility and control through specifically tailored parameters. This is done through two types of control curves: a fitted theoretical curve for the mass of deposited material, and a control curve extracted from the images for the color. This way, the user has a set of simple and intuitive parameters and tools to control the flow phenomena on the target image. To illustrate our technique, we present a complete set of images that somewhat cover a large range of flow phenomena in urban environments.