CEIG15
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Item A 3DWeb Application for Weather Forecast Based on WebGL(The Eurographics Association, 2015) Graciano, Alejandro; Rueda, Antonio J.; Feito, Francisco R.; Martínez, Francisco; Mateu Sbert and Jorge Lopez-MorenoManagement, interpretation and visualization of geoscientific and atmospherical information is a major problem for the geoscientist and for a correct diffusion, due to its high volume, complexity, spatiotemporal dimension and three-dimensional nature. As a result, development of software tools for integration, exploration and graphical analysis of the growing amount of available geodata is of great importance. In the last decade a trend towards the implementation of these tools as web applications has consolidated because of its benefits: universal access, permanent availability and ease of collaborative use. However until recently Web development technologies have been ill-equipped for implementing interactive 2D and 3D applications dealing with large amounts of data as required by many geoscience applications. The support of WebGL by most modern browsers has changed this situation and promises to revolutionize the Web in the next few years with a new generation of visually appealing, high performance interactive applications. In this work we describe the technologies for 3D Web and their use in the context of atmospherical data using a 3D weather information application as case study.Item Bidirectional Clustering for Scalable VPL-based Global Illumination(The Eurographics Association, 2015) Jarabo, Adrian; Buisan, Raul; Gutierrez, Diego; Mateu Sbert and Jorge Lopez-MorenoVirtual Point Lights (VPL) methods approximate global illumination (GI) in a scene by using a large number of virtual lights modeling the reflected radiance of a surface. These methods are efficient, and allow computing noise-free images significantly faster that other methods. However, they scale linearly with the number of virtual lights and with the number of pixels to be rendered. Previous approaches improve the scalability of the method by hierarchically evaluating the virtual lights, allowing sublinear performance with respect the lights being evaluated. In this work, we introduce a novel bidirectional clustering approach, by hierarchically evaluating both the virtual lights and the shading points. This allows reusing radiance evaluation between pixels, and obtaining sublinear costs with respect to both lights and camera samples. We demonstrate significantly better performance than state-of-the-art VPL clustering methods with several examples, including high-resolution images, distributed effects, and rendering of light fields.Item Compressive High Speed Video Acquisition(The Eurographics Association, 2015) Serrano, Ana; Gutierrez, Diego; Masia, Belen; Mateu Sbert and Jorge Lopez-MorenoTraditional video capture is limited by the trade-off between spatial and temporal resolution. When capturing videos of high temporal resolution, the spatial resolutions decreases due to bandwidth limitations in the capture system. Achieving both high spatial and temporal resolution is only possible with highly specialized and very expensive hardware; although the bandwidth is higher, the same basic trade-off remains. In this paper, we make use of a single-shot, high-speed video capture system, in order to overcome this limitation. It is based on compressive sensing, and relies on dictionary learning for sparse video representation. This allows capturing a video sequence by coding the temporal information in a single frame, and then reconstructing the full video sequence from this single coded image. We perform an in-depth analysis of the parameters of influence in the system, providing insights for future developments of similar systems.Item Easy Going Vector Graphics as Textures on the GPU(The Eurographics Association, 2015) Patow, Gustavo; Mateu Sbert and Jorge Lopez-MorenoOne common problem of raster images when used as textures is its resolution dependence, which could produce artifacts such as blurring. On the contrary, vector graphics are resolution independent, and their direct use for real-time texture mapping would be desirable to avoid sampling artifacts. Usually, they composite images from layers of paths and strokes defined with different kinds of lines. Here I present a simple yet powerful technique for representing vector graphics as textures that organizes the graphic into a coarse grid of cells, structuring each cell into simple cell-sized BSP trees, evaluated at runtime within a pixel shader. Advantages include coherent low-bandwidth memory access and, although my implementation is limited to polygonal shapes, the ability to map general vector graphics onto arbitrary surfaces. A fast construction algorithm is presented, and the space and time efficiency of the representation are demonstrated on many practical examples.Item Efficient and Robust Position-Based Fluids for VFX(The Eurographics Association, 2015) Alduán, Iván; Tena, Angel; Otaduy, Miguel A.; Mateu Sbert and Jorge Lopez-MorenoDesigning a fluid simulator with VFX production pipelines in mind is a difficult task where goals like efficiency, robustness and scalability compromise each other. Many impressive fluid simulation methods have been presented in research papers before, but often they do not meet the production and flexibility demands of artists working on actual VFX production pipelines. In this paper we present a particle-based fluid simulation framework, based on the well known Position-Based Fluids (PBF) method, designed to address VFX production demands. Our framework puts special care on data structure design and implementation details. It highlights cache-efficient GPU-friendly data structures, an improved Z-index sort spatial voxelization technique, tuned-up simulation algorithms, and collision treatment based on VDB fields. Altogether, they empower the artist with a very efficient fluid solver, but also with the robustness and versatility needed for simulating very diverse scenes and effects.Item Frontmatter: XXV Spanish Computer Graphics Conference(The Eurographics Association, 2015) Mateu Sbert; Miguel Chover; -Item Industrial Facility Modeling Using Procedural Methods(The Eurographics Association, 2015) Bishop, M. Scott; Max, Nelson; Mateu Sbert and Jorge Lopez-MorenoWe present an end-to-end system for procedurally modeling an industrial facility. The system is a collection of utilities that work together to assemble, lay out, and model a typical industrial facility (e.g. a wastewater treatment plant). A plug-in to the CityEngine (R) procedural modeling application was built in Java (TM) using an open-source framework. The plug-in provides the interface to access the facility assembly and layout engines, the facility rule file and Python script generators, and the OBJ footprint exporter. The system provides functionality for placing the facility model into an existing 3D scene using an established facility location algorithm that maximizes the minimum distance from existing structures in the scene.Item An Interactive Algorithm for Virtual Patient Positioning(The Eurographics Association, 2015) Casafranca, Juan José; Sújar, Aaron; García, Marcos; Mateu Sbert and Jorge Lopez-MorenoIn the last years, Virtual Reality medical simulators are gaining importance, training new physicians in a safe environment. In order to improve the trainees' skills, these applications let them perform a specific medical procedure in different virtual patients with different anatomical variation. Typically, virtual patients are generated from medical imaging data sets, such as MRI (magnetic resonance imaging), CT (computed tomography) or US (ultra sound). Usually, these data are generally captured in specific subject position. This pose is different from the subjects' position required in the simulated specific medical procedure. This paper proposes a novel technique that allows adapting the virtual patient anatomy to any desired pose. Our algorithm follows a geometrically based approach with the intention of: (i) being independent of a proper mechanical description of the tissues which is rarely available and (ii) keeping our user interface running at interactive rates. We adapted the skeletal animation workflow to deal with internal anatomy models. Most of the stages of this workflow have been automated. The user intervention has been limited to the interactive pose selection process. Additionally, in order to refine the solutions provided by our geometric approach, we have designed an optimization phase to achieve more appealing results.Item Low Cost Decomposition of Direct and Global Illumination in Real Scenes(The Eurographics Association, 2015) Garces, Elena; Martin, Fernando; Gutierrez, Diego; Mateu Sbert and Jorge Lopez-MorenoRecent advances in the field of computational light transport have made it possible to solve previously unsolvable problems thanks to incorporating new devices and techniques. One of these problems is the decomposition of the illumination into its local and global components in real scenes. Previous work has managed to perform such a decomposition by projecting several light patterns on a target scene and processing its captures. In this work we build on that approach and propose two novel contributions: first, a new interpolation method, which allows the decomposition of the light components from a single capture of the projected scene into the native resolution, without requiring down-sampling; second, we propose an implementation of the algorithm for a mobile platform.Item NeuroScheme: Efficient Multiscale Representations for the Visual Exploration of Morphological Data in the Human Brain Neocortex(The Eurographics Association, 2015) Pastor, Luis; Mata, Susana; Toharia, Pablo; Bayona, Sofia; Brito, Juan Pedro; Garcia-Cantero, Juan Jose; Mateu Sbert and Jorge Lopez-MorenoThe analysis of data sets from such a complex domain as neuroscience is severely hampered by the brain complexity and by the huge amount of data originated in current experiments and simulations. The complexity of the brain stems not only from the enormous number of relevant entities that integrate it (for example, around 10Item 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 PREFR: A Flexible Particle Rendering Framework(The Eurographics Association, 2015) Galindo, Sergio E.; Toharia, Pablo; Lopez-Moreno, Jorge; Robles, Oscar D.; Pastor, Luis; Mateu Sbert and Jorge Lopez-MorenoWe present PREFR (Particle REndering FRamework): a first approach to a general-purpose particle rendering framework on the standard OpenGL architecture, designed with the goal of being easily configured by the user without compromising efficiency. In this paper, we analyze and discuss the performance of each stage involved in particle rendering in order to improve its efficiency for future versions with additional GPGPU computation steps or multicore parallelization techniques. Finally, we show the potential of our particle engine by tackling two very different problems: The rendering of neuronal electrical impulses in physiological models of the human brain, and the visualization of emergent patterns for information analysis, specifically emphasizing structured information in a complex data set.Item Real-time Inextensible Hair with Volume and Shape(The Eurographics Association, 2015) Sánchez-Banderas, Rosa María; Barreiro, Héctor; García-Fernández, Ignacio; Pérez, Mariano; Mateu Sbert and Jorge Lopez-MorenoHair simulation is a common topic extensively studied in computer graphics. One of the many challenges in this field is simulating realistic hair in a real-time environment. In this paper, we propose a unified simulation scheme to consider three of the key features in hair simulation; inextensibility, shape preservation and hair-hair interaction. We use an extension to the Dynamic Follow the Leader (DFTL) method to include shape preservation. Our implementation is also coupled with a Lagrangian approach to address the hair-hair interaction dynamics. A GPU-friendly scheme is proposed that is able to exploit the massive parallelism these devices offer, being able to simulate thousands of strands in real-time. The method has been integrated in a game development platform with a shading model for rendering and several test applications have been developed using this implementation.Item Simulation of the Commercial Market Evolution in a City(The Eurographics Association, 2015) Soriano, Carlos; Patow, Gustavo; Mateu Sbert and Jorge Lopez-MorenoSimulating the evolution of urban landscapes is a challenging objective with a large impact not only for Computer Graphics (for its applications in the filming and gaming industries), but also for urban planning, economical and historical studies, urban physics, and many other. However, this target has remained elusive because of the large complexity implied by urban structures and their evolutions. We present a system that aims at simulating the evolution of the commercial structure in a modern city. In particular, given an initial distribution of shops, it studies the evolution when larger commercial areas, like malls, are introduced. This is computed using the Huff model as a measure of the attraction each commerce has on potential consumers, and an agent-based simulation to determine how these aspects affect their choices. Then, after a given simulation time, the system decides whether the shop has retained an income such that it can continue operating, or has gone bankrupt. Our system is used to study the evolution of the commercial structure of Barcelona city over the last century. 1. Introduction Procedural urban modeling has presented us with astonishing results over the last decade, starting with the seminal work by Parish and Muller [PM01] and Muller et al. [MWH 06], and continuing with the recent advances in acquisition [MWA 12], non-regular modeling [LCOZ 11], user interfaces [Pat12], among others. However, in spite of all those improvements, several problems remain open [PBP14], one of the most important ones is simulating the evolution of urban landscapes over time. With only a few exceptions [WMWG09,BWK14], this topic has barely been touched, in spite of its crucial importance for history and archeology, urban planning, socio-economical studies, and many other social-related disciplines. Among these unexplored aspects, the problem of simulating the evolution of the commerce structure in a city is a prominent one, as it is attractive for being computationally tractable and crucial for socio-economic studies. But this study has applications that are broader than a pure social analysis, as the resulting distributions can be used to also model its appearance over time, which is interesting for computer graphics because of its applications to film and videogames, two of the leading industries in the field. y carlos.Item Stereoscopic visualization systems: Comparison between a Large Passive Display and a Head Mounted Display(The Eurographics Association, 2015) Rodríguez-Andrés, David; Cárdenas, Sonia; Juan, M. Carmen; Pérez-Hernández, E.; Méndez-López, Magda; Lluch, Javier; Mateu Sbert and Jorge Lopez-MorenoIn this paper, we present an application that uses two visualization systems. The first one has a large passive display. In the second system, we use a virtual reality head mounted display (Oculus Rift). We report the results of a study to determine the feeling of immersion in an application for testing spatial memory. 168 adults participated in the study. They are 25:28 4:07 years old. After testing each system, they answered a questionnaire about their feeling of immersion in the 3D environment. We found statistically significant differences between the visualization systems. The participants gave higher scores when using Oculus Rift that using passive 3D. Then, we can conclude that the participants have perceived better the 3D with the Oculus Rift.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.