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Item Interactive Modeling of Mechanical Objects(The Eurographics Association and John Wiley & Sons Ltd., 2016) Ureta, Francisca Gil; Tymms, Chelsea; Zorin, Denis; Maks Ovsjanikov and Daniele PanozzoObjects with various types of mechanical joints are among the most commonly built. Joints implement a vocabulary of simple constrained motions (kinematic pairs) that can be used to build more complex behaviors. Defining physically correct joint geometry is crucial both for realistic appearance of models during motion, as these are typically the only parts of geometry that stay in contact, and for fabrication. Direct design of joint geometry often requires more effort than the design of the rest of the object geometry, as it requires design of components that stay in precise contact, are aligned with other parts, and allow the desired range of motion. We present an interactive system for creating physically realizable joints with user-controlled appearance. Our system minimizes or, in most cases, completely eliminates the need for the user to manipulate low-level geometry of joints. This is achieved by automatically inferring a small number of plausible combinations of joint dimensions, placement and orientation from part geometry, with the user making the final high-level selection based on object semantic. Through user studies, we demonstrate that functional results with a satisfying appearance can be obtained quickly by users with minimal modeling experience, offering a significant improvement in the time required for joint construction, compared to standard modeling approaches.Item Marching Pentatopes for Continuous Morphing of Isosurfaces From Four Dimensional Data in HTML5/WebGL(The Eurographics Association, 2017) Watters, Aaron R.; Barbora Kozlikova and Tobias Schreck and Thomas WischgollAnimations which show three dimensional volumes continuously changing over time facilitate the exploration and analysis of complex data sets such as calcium image data of neural activity and phase contrast magnetic resonance imaging of blood flows. This paper explains the marching pentatopes method for representing the iso-surfaces of a four dimensional data set as a triangulated surface smoothly deforming as time progresses. The morphing triangulations generated by the this method may be rendered using the morph geometry capabilities provided by the three.js javascript library for cross platform HTML5/WebGL presentation in standard web browsers [Cab17].Item Geometry and Attribute Compression for Voxel Scenes(The Eurographics Association and John Wiley & Sons Ltd., 2016) Dado, Bas; Kol, Timothy R.; Bauszat, Pablo; Thiery, Jean-Marc; Eisemann, Elmar; Joaquim Jorge and Ming LinVoxel-based approaches are today's standard to encode volume data. Recently, directed acyclic graphs (DAGs) were successfully used for compressing sparse voxel scenes as well, but they are restricted to a single bit of (geometry) information per voxel. We present a method to compress arbitrary data, such as colors, normals, or reflectance information. By decoupling geometry and voxel data via a novel mapping scheme, we are able to apply the DAG principle to encode the topology, while using a palette-based compression for the voxel attributes, leading to a drastic memory reduction. Our method outperforms existing state-of-the-art techniques and is well-suited for GPU architectures. We achieve real-time performance on commodity hardware for colored scenes with up to 17 hierarchical levels (a 128K3 voxel resolution), which are stored fully in core.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 Aortic Dissection Maps: Comprehensive Visualization of Aortic Dissections for Risk Assessment(The Eurographics Association, 2016) Mistelbauer, Gabriel; Schmidt, Johanna; Sailer, Anna-Margaretha; Bäumler, Kathrin; Walters, Shannon; Fleischmann, Dominik; Stefan Bruckner and Bernhard Preim and Anna Vilanova and Helwig Hauser and Anja Hennemuth and Arvid LundervoldAortic dissection is a life threatening condition of the aorta, characterized by separation of its wall layers into a true and false lumen. A subset of patients require immediate surgical or endovascular repair. All survivors of the acute phase need long-term surveillance with imaging to monitor chronic degeneration and dilatation of the false lumen and prevent late adverse events such as rupture, or malperfusion. We introduce four novel plots displaying features of aortic dissections known or presumed to be associated with risk of future adverse events: Aortic diameter, the blood supply (outflow) to the aortic branches from the true and false lumen, the previous treatment, and an estimate of adverse event-free probabilities in one, two and 5 years. Aortic dissection maps, the composite visualization of these plots, provide a baseline for visual comparison of the complex features and associated risk of aortic dissection. These maps may lead to more individualized monitoring and improved, patient-centric treatment planning in the future.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 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 MCFTLE: Monte Carlo Rendering of Finite-Time Lyapunov Exponent Fields(The Eurographics Association and John Wiley & Sons Ltd., 2016) Günther, Tobias; Kuhn, Alexander; Theisel, Holger; Kwan-Liu Ma and Giuseppe Santucci and Jarke van WijkTraditionally, Lagrangian fields such as finite-time Lyapunov exponents (FTLE) are precomputed on a discrete grid and are ray casted afterwards. This, however, introduces both grid discretization errors and sampling errors during ray marching. In this work, we apply a progressive, view-dependent Monte Carlo-based approach for the visualization of such Lagrangian fields in time-dependent flows. Our approach avoids grid discretization and ray marching errors completely, is consistent, and has a low memory consumption. The system provides noisy previews that converge over time to an accurate high-quality visualization. Compared to traditional approaches, the proposed system avoids explicitly predefined fieldline seeding structures, and uses a Monte Carlo sampling strategy named Woodcock tracking to distribute samples along the view ray. An acceleration of this sampling strategy requires local upper bounds for the FTLE values, which we progressively acquire during the rendering. Our approach is tailored for high-quality visualizations of complex FTLE fields and is guaranteed to faithfully represent detailed ridge surface structures as indicators for Lagrangian coherent structures (LCS). We demonstrate the effectiveness of our approach by using a set of analytic test cases and real-world numerical simulations.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.