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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 HIJSON: Cartographic Document for Web Modeling of Interactive Indoor Mapping(The Eurographics Association, 2015) Spini, Federico; Sportillo, Marco; Virgadamo, Marco; Marino, Enrico; Bottaro, Antonio; Paoluzzi, Alberto; Andrea Giachetti and Silvia Biasotti and Marco TariniThis paper introduces HIJSON, a novel indoor cartographic document format with several enhancements. The document is generated using LAR (Linear Algebraic Representation), so allowing for cellular complexes with general topology and shape. A software framework FIVE is also presented, that relies on HIJSON documents and is entirely based on web technologies. With respect to current cartographic formats, HIJSON suggests four major enhancements: (a) exposes a hierarchical structure; (b) uses local metric coordinate systems; (c) may import external geometric models; (d) accepts semantic extensions. The semantic extensions supported by the FIVE framework architecture encapsulate the details about communication protocols, rendering style, and exchanged and displayed information, allowing the HIJSON format to be extended with any sort of models of objects, sensors or behaviors.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 Natural Phenomena as Metaphors for Visualization of Trend Data in Interactive Software Maps(The Eurographics Association, 2015) Würfel, Hannes; Trapp, Matthias; Limberger, Daniel; Döllner, Jürgen; Rita Borgo and Cagatay TurkaySoftware maps are a commonly used tool for code quality monitoring in software-development projects and decision making processes. While providing an important visualization technique for the hierarchical system structure of a single software revision, they lack capabilities with respect to the visualization of changes over multiple revisions. This paper presents a novel technique for visualizing the evolution of the software system structure based on software metric trends. These trend maps extend software maps by using real-time rendering techniques for natural phenomena yielding additional visual variables that can be effectively used for the communication of changes. Therefore, trend data is automatically computed by hierarchically aggregating software metrics. We demonstrate and discuss the presented technique using two real world data sets of complex software systems.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 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 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 Low-cost Experimental Setups for Mid-air 3D Reconstruction(The Eurographics Association, 2015) Dancu, Alexandru; Fratarcangeli, Marco; Fourgeaud, Mickaël; Franjcic, Zlatko; Chindea, Daniel; Fjeld, Morten; Andrea Giachetti and Silvia Biasotti and Marco TariniThe reconstruction of the physical environment using a depth sensor involves data-intensive computations which are difficult to implement on mobile systems (e.g., tracking and aligning the position of the sensor with the depth maps). In this paper, we present two practical experimental setups for scanning and reconstructing real objects employing low-price, off-the-shelf embedded components and open-source libraries. As a test case, we scan and reconstruct a 23 m high statue using an octocopter without employing external hardwareItem RameshCleaner: Conservative Fixing of Triangular Meshes(The Eurographics Association, 2015) Centin, Marco; Signoroni, Alberto; Andrea Giachetti and Silvia Biasotti and Marco TariniIn this work, after a careful examination of the most common errors and flaws which typically occur in meshes produced by 3D scanning processes, we propose a set of fixing tools which solve effectively several important mesh defects while preserving the original data. The proposed tools are then organized and activated in the RameshCleaner pipeline allowing the user to take advantage of a semi-automated fixing solution, optimized for speed and efficiency, as well as of the possibility to selectively activate individual tools. The comparison, over a set of representative scanned models, with free and commercial semi-automated fixing solutions gives a significant evidence of the defect abatement and computational speed characteristics of the proposed system.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.