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Item Parallelized Global Brain Tractography(The Eurographics Association, 2013) Philips, Stefan; Hlawitschka, Mario; Scheuermann, Gerik; Michael Bronstein and Jean Favre and Kai HormannMost brain tractography algorithms suffer from lower accuracy, because they use only information in a certain neighborhood and reconstruct the tracts independently. Global brain tractography algorithms compensate the lack of accuracy of those local algorithms in certain areas by optimizing the whole tractogram. The global tractography approach by Reisert et al. showed the best results in the Fiber Cup contest, but the runtime is still a matter for a medical application. In this paper we present the non-trivial parallelization of this global tractography algorithm. The parallelization exploits properties of the algorithm and modifies the algorithm where necessary. We compare the runtimes of the serial and the parallel variant and show that the outcomes of the parallel variant are of the same quality as those of the serial algorithm. The experiments proof also that the parallelization scales well for real world datasets.Item Camera Motion Graphs(The Eurographics Association, 2014) Sanokho, Cunka Bassirou; Desoche, Clement; Merabti, Billal; Li, Tsai-yen; Christie, Marc; Vladlen Koltun and Eftychios SifakisThis paper presents Camera Motion Graphs, a technique to easily and efficiently generate cinematographic sequences in real-time dynamic 3D environments. A camera motion graph consists of (i) pieces of original camera trajectories attached to one or multiple targets, (ii) generated continuous transitions between camera trajectories and (iii) transitions representing cuts between camera trajectories. Pieces of original camera trajectories are built by extracting camera motions from real movies using vision-based techniques, or relying on motion capture techniques using a virtual camera system. A transformation is proposed to recompute all the camera trajectories in a normalized representation, making camera paths easily adaptable to new 3D environments through a specific retargeting technique. The camera motion graph is then constructed by sampling all pairs of camera trajectories and evaluating the possibility and quality of continuous or cut transitions. Results illustrate the simplicity of the technique, its adaptability to different 3D environments and its efficiency.Item On Establishing Visualization Requirements: A Case Study in Product Costing(The Eurographics Association, 2017) Vosough, Zana; Groh, Rainer; Schulz, Hans-Jörg; Barbora Kozlikova and Tobias Schreck and Thomas WischgollThe process of identifying visualization requirements is an important part of every visualization researcher's and practitioner's job. Nevertheless, the scientific literature is rather sparse on this topic, usually resorting to some form of user-centered design that is rarely further detailed. In this paper, we give an account of our procedure, our results, our problems and solutions for gathering visualization requirements in an ongoing business project to introduce visualization to the field of product costing. By providing insight in our experiences and extracting general points of advice from them, we aim to give some practical guidance for establishing requirements in real-world visualization projects.Item Information Visualization Evaluation Using Crowdsourcing(The Eurographics Association and John Wiley & Sons Ltd., 2018) Borgo, Rita; Micallef, Luana; Bach, Benjamin; McGee, Fintan; Lee, Bongshin; Robert S. Laramee and G. Elisabeta Marai and Michael SedlmairVisualization researchers have been increasingly leveraging crowdsourcing approaches to overcome a number of limitations of controlled laboratory experiments, including small participant sample sizes and narrow demographic backgrounds of study participants. However, as a community, we have little understanding on when, where, and how researchers use crowdsourcing approaches for visualization research. In this paper, we review the use of crowdsourcing for evaluation in visualization research. We analyzed 190 crowdsourcing experiments, reported in 82 papers that were published in major visualization conferences and journals between 2006 and 2017. We tagged each experiment along 36 dimensions that we identified for crowdsourcing experiments.We grouped our dimensions into six important aspects: study design & procedure, task type, participants, measures & metrics, quality assurance, and reproducibility. We report on the main findings of our review and discuss challenges and opportunities for improvements in conducting crowdsourcing studies for visualization research.Item 3D Model for Solar Energy Potential on Buildings from Urban LiDAR Data(The Eurographics Association, 2016) Bill, Andreas; Mohajeri, Nahid; Scartezzini, Jean-Louis; Vincent Tourre and Filip BiljeckiOne of the most promising sustainable energies that can be considered in urban environments is solar energy. A 3D model for solar energy potential on building envelopes based on urban LiDAR data was developed in this study. The developed algorithm can be used to model solar irradiation with high spatio-temporal resolution for roof-, facade-, and ground surfaces simultaneously, while taking into account the surrounding vegetation. Global solar irradiation is obtained for regularly spaced points on building- and ground surfaces with a spatial resolution of 1m2 and a time resolution of 1 hour. The algorithm has been implemented in Matlab and results were generated for two different test areas in the city of Geneva, Switzerland. The results for these specific areas show that, even in a dense urban area, the upper parts of south-east to south-west oriented facades receive 600 to 1000 kWh/m2/year of solar input, which is suitable for active solar installations. The results also show that south oriented facades can get higher solar input during winter months than the low inclined roof surfaces. This demonstrates that, depending on the latitude, facades can have a significant impact on the solar potential of buildings in urban areas, particularly for a sustainable energy planning application.Item Similarity Voting based Viewpoint Selection for Volumes(The Eurographics Association and John Wiley & Sons Ltd., 2016) Tao, Yubo; Wang, Qirui; Chen, Wei; Wu, Yingcai; Lin, Hai; Kwan-Liu Ma and Giuseppe Santucci and Jarke van WijkPrevious viewpoint selection methods in volume visualization are generally based on some deterministic measures of viewpoint quality. However, they may not express the familiarity and aesthetic sense of users for features of interest. In this paper, we propose an image-based viewpoint selection model to learn how visualization experts choose representative viewpoints for volumes with similar features. For a given volume, we first collect images with similar features, and these images reflect the viewpoint preferences of the experts when visualizing these features. Each collected image tallies votes to the viewpoints with the best matching based on an image similarity measure, which evaluates the spatial shape and appearance similarity between the collected image and the rendered image from the viewpoint. The optimal viewpoint is the one with the most votes from the collected images, that is, the viewpoint chosen by most visualization experts for similar features. We performed experiments on various volumes available in volume visualization, and made comparisons with traditional viewpoint selection methods. The results demonstrate that our model can select more canonical viewpoints, which are consistent with human perception.Item Instant Visualization of Secondary Structures of Molecular Models(The Eurographics Association, 2015) Hermosilla, Pedro; Guallar, V.; Vinacua, Alvar; Vázquez, Pere-Pau; Katja Bühler and Lars Linsen and Nigel W. JohnMolecular Dynamics simulations are of key importance in the drug design field. Among all possible representations commonly used to inspect these simulations, Ribbons has the advantage of giving the expert a good overview of the conformation of the molecule. Although several techniques have been previously proposed to render ribbons, all of them have limitations in terms of space or calculation time, making them not suitable for real-time interaction with simulation software. In this paper we present a novel adaptive method that generates ribbons in real-time, taking advantage of the tessellation shader. The result is a fast method that requires no precomputation, and that generates high quality shapes and shading.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 Improved Sparse Seeding for 3D Electrostatic Field Lines(The Eurographics Association, 2015) Scharnowski, Katrin; Boblest, Sebastian; Ertl, Thomas; E. Bertini and J. Kennedy and E. PuppoWe present an improved seeding strategy for sparse visualization of electrostatic fields. By analyzing the curvature of the field lines, we extract points of extremal field strength between charges of different sign and use them to seed field lines, which consequently connect the corresponding charges. The resulting sparse representation can be seen as an extension to classic vector field topology depicting properties otherwise hidden. Finally, by applying our method to a synthetic data set, we show its benefits over previously published work.Item Visualizing High-Dimensional Data: Advances in the Past Decade(The Eurographics Association, 2015) Liu, Shusen; Maljovec, Dan; Wang, Bei; Bremer, Peer-Timo; Pascucci, Valerio; R. Borgo and F. Ganovelli and I. ViolaMassive simulations and arrays of sensing devices, in combination with increasing computing resources, have generated large, complex, high-dimensional datasets used to study phenomena across numerous fields of study. Visualization plays an important role in exploring such datasets. We provide a comprehensive survey of advances in high-dimensional data visualization over the past 15 years. We aim at providing actionable guidance for data practitioners to navigate through a modular view of the recent advances, allowing the creation of new visualizations along the enriched information visualization pipeline and identifying future opportunities for visualization research.