EG2009
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Item Complex Barycentric Coordinates with Applications to Planar Shape Deformation(The Eurographics Association and Blackwell Publishing Ltd, 2009) Weber, Ofir; Ben-Chen, Mirela; Gotsman, CraigItem Applet Competition as an Educational Tool in Creating Novel e-Textbook(The Eurographics Association, 2009) Czanner, Silvester; Ferko, Andrej; Stugel, Juraj; Nunukova, Pavla; G. Domik and R. ScateniWe introduce a long-term competition-oriented project, using learning by doing (applets). The output of this project is updated every year at http://www.netgraphics.sk/. Many undergraduate students at the University of Warwick and the Comenius University compete in developing the e-Textbook, called Computer Graphics Virtual Textbook. The current version offers supplementary material for particular CG courses but it is also an independent source of information for all people interested in CG. There is currently 126 students enrolled for this competition. Every year, the number of valuable applets or applet innovations is lower than the total number of students. The three winners of 2008 round of applet competition will be announced before Christmas (and their creations will be presented at the SCCG09 conference). The best units of this project will be submitted to CGEMS.Item Completion and Reconstruction with Primitive Shapes(The Eurographics Association and Blackwell Publishing Ltd, 2009) Schnabel, Ruwen; Degener, Patrick; Klein, ReinhardWe consider the problem of reconstruction from incomplete point-clouds. To find a closed mesh the reconstruction is guided by a set of primitive shapes which has been detected on the input point-cloud (e.g. planes, cylinders etc.). With this guidance we not only continue the surrounding structure into the holes but also synthesize plausible edges and corners from the primitives intersections. To this end we give a surface energy functional that incorporates the primitive shapes in a guiding vector field. The discretized functional can be minimized with an efficient graph-cut algorithm. A novel greedy optimization strategy is proposed to minimize the functional under the constraint that surface parts corresponding to a given primitive must be connected. From the primitive shapes our method can also reconstruct an idealized model that is suitable for use in a CAD system.Item Shape Decomposition using Modal Analysis(The Eurographics Association and Blackwell Publishing Ltd, 2009) Huang, Qi-Xing; Wicke, Martin; Adams, Bart; Guibas, LeonidasWe introduce a novel algorithm that decomposes a deformable shape into meaningful parts requiring only a single input pose. Using modal analysis, we are able to identify parts of the shape that tend to move rigidly. We define a deformation energy on the shape, enabling modal analysis to find the typical deformations of the shape. We then find a decomposition of the shape such that the typical deformations can be well approximated with deformation fields that are rigid in each part of the decomposition. We optimize for the best decomposition, which captures how the shape deforms. A hierarchical refinement scheme makes it possible to compute more detailed decompositions for some parts of the shape.Although our algorithm does not require user intervention, it is possible to control the process by directly changing the deformation energy, or interactively refining the decomposition as necessary. Due to the construction of the energy function and the properties of modal analysis, the computed decompositions are robust to changes in pose as well as meshing, noise, and even imperfections such as small holes in the surface.Item Spectral-Based Group Formation Control(The Eurographics Association and Blackwell Publishing Ltd, 2009) Takahashi, Shigeo; Yoshida, Kenichi; Kwon, Taesoo; Lee, Kang Hoon; Lee, Jehee; Shin, Sung YongGiven a pair of keyframe formations for a group consisting of multiple individuals, we present a spectral-based approach to smoothly transforming a source group formation into a target formation while respecting the clusters of the involved individuals. The proposed method provides an effective means for controlling the macroscopic spatiotemporal arrangement of individuals for applications such as expressive formations in mass performances and tactical formations in team sports. Our main idea is to formulate this problem as rotation interpolation of the eigenbases for the Laplacian matrices, each of which represents how the individuals are clustered in a given keyframe formation. A stream of time-varying formations is controlled by editing the underlying adjacency relationships among individuals as well as their spatial positions at each keyframe, and interpolating the keyframe formations while producing plausible collective behaviors over a period of time. An interactive system of editing existing group behaviors in a hierarchical fashion has been implemented to provide flexible formation control of large crowds.Item Video-Realistic Image-based Eye Animation System(The Eurographics Association, 2009) Weissenfeld, Axel; Liu, Kang; Ostermann, J.; P. Alliez and M. MagnorIn this work we elaborate on a novel image-based system for creating video-realistic eye animations to arbitrary spoken output. These animations are useful to give a face to multimedia applications such as virtual operators in dialog systems. Our eye animation system consists of two parts: eye control unit and rendering engine. The designed eye control unit is based on the statistical analysis of recorded human subjects. We design a new model, which fully automatically couples eye blinks and movements with phonetic as well as prosodic information extracted from spoken language. Subjective tests showed that participants are not able to distinguish between real eye motions and our animations, which has not been achieved before.Item ImaGINe-S: Imaging Guided Interventional Needle Simulation(The Eurographics Association, 2009) Bello, Fernando; Bulpitt, Andrew; Gould, Derek A.; Holbrey, Richard; Hunt, Carrie; How, Thien; John, Nigel W.; Johnson, Sheena; Phillips, Roger; Sinha, Amrita; Vidal, Franck; Villard, Pierre-Frédéric; Woolnough, Helen; Zhang, Yan; K. Bühler and D. BartzWe present an integrated system for training visceral needle puncture procedures. Our aim is to provide a cost effective and validated training tool that uses actual patient data to enable interventional radiology trainees to learn how to carry out image-guided needle puncture. The input data required is a computed tomography scan of the patient that is used to create the patient specific models. Force measurements have been made on real tissue and the resulting data is incorporated into the simulator. Respiration and soft tissue deformations are also carried out to further improve the fidelity of the simulator.Item Interactive Shape Modeling and Deformation(The Eurographics Association, 2009) Sorkine, Olga; Botsch, Mario; K. Museth and D. WeiskopfWe present a tutorial that covers the latest research advances in interactive 3D shape modeling and deformation, a highly relevant topic for CAGD, engineering applications, and computer animation for movies or games. We focus on the essence of the underlying theory and principles, as well as the practical aspects of algorithm design and development involved in interactive shape editing. Our presentation is meant to be comparative, juxtaposing various recently proposed approaches and revealing their pros and cons in different modeling scenarios. As such, our class is intended for both researchers and practitioners, helping to sift through the large body of work on interactive modeling by a systematic, hands-on overview.Item A Gaze-Contingent Display Compensating for Scotomata(The Eurographics Association, 2009) Duchowski, Andrew T.; Eaddy, Tiras D.; P. Alliez and M. MagnorA Gaze-Contingent Display (GCD) is developed in GLSL to compensate for scotomata (loss of retinal visual acuity) such as brought on by Age-related Macular Degeneration (AMD). The compensatory GCD introduces a magnification ring slaved to the viewer s gaze point.Item GPU Ray-Casting for Scalable Terrain Rendering(The Eurographics Association, 2009) Dick, Christian; Krüger, Jens; Westermann, Rüdiger; D. Ebert and J. KrügerWith the ever increasing resolution of scanned elevation models, geometry throughput on the GPU is becoming a severe performance limitation in 3D terrain rendering. In this paper, we investigate GPU ray-casting as an alternative to overcome this limitation, and we demonstrate its advanced scalability compared to rasterization-based techniques. By integrating ray-casting into a tile-based GPU viewer that effectively reduces bandwidth requirements in out-of-core terrain visualization, we show that the rendering performance for large, high-resolution terrain fields can be increased significantly. We show that a screen-space error below one pixel permits piecewise constant interpolation of initial height samples. Furthermore, we exploit the texture mapping capabilities on recent GPUs to perform deferred anisotropic texture filtering, which allows for the rendering of digital elevation models and corresponding photo textures. In two key experiments we compare GPU-based ray-casting to a rasterizationbased approach in the scope of terrain rendering, and we demonstrate the scalability of the proposed ray-caster with respect to display and data resolution.Item Procedural Modeling of Leather Texture with Structural Elements(The Eurographics Association, 2009) Sakurai, Kaisei; Miyata, Kazunori; Kawai, Naoki; Matsufuji, Kazuo; Eric Galin and Jens SchneiderThis paper proposes a simple generation method for realistic leather texture. Leather surface consists of five structural elements, which are cristae, sulci, wrinkles, pockets and pores, which characterize the visual impression of the leather texture.We classified structural elements by observing real leather surface. To represent the elements, the method extracts features of real textures in order to generate an outline of each element. Then the method computes each element is three-dimensional shapes by a function which defines a continuous surface. Our method generates detailed leather texture, and is easy to handle, with simple procedures and intuitive parameters.Item Volume Conserving Simulation of Deformable Bodies(The Eurographics Association, 2009) Diziol, Raphael; Bender, Jan; Bayer, Daniel; P. Alliez and M. MagnorWe present a new method for simulating volume conserving deformable bodies using an impulse-based approach. In order to simulate a deformable body a tetrahedral model is generated from an arbitrary triangle mesh. All resulting tetrahedrons are assigned to volume constraints which ensure the conservation of the total volume. For the simulation of such a constraint impulses are computed and applied to the particles of the assigned tetrahedrons. The algorithm is easy to implement and ensures exact volume conservation in each simulation step.Item LazyBrush: Flexible Painting Tool for Hand-drawn Cartoons(The Eurographics Association and Blackwell Publishing Ltd, 2009) Sykora, Daniel; Dingliana, John; Collins, StevenIn this paper we present LazyBrush, a novel interactive tool for painting hand-made cartoon drawings and animations. Its key advantage is simplicity and flexibility. As opposed to previous custom tailored approaches [SBv05, QWH06] LazyBrush does not rely on style specific features such as homogenous regions or pattern continuity yet still offers comparable or even less manual effort for a broad class of drawing styles. In addition to this, it is not sensitive to imprecise placement of color strokes which makes painting less tedious and brings significant time savings in the context cartoon animation. LazyBrush originally stems from requirements analysis carried out with professional ink-and-paint illustrators who established a list of useful features for an ideal painting tool. We incorporate this list into an optimization framework leading to a variant of Potts energy with several interesting theoretical properties. We show how to minimize it efficiently and demonstrate its usefulness in various practical scenarios including the ink-and-paint production pipeline.Item Out-of-core Data Management for Path Tracing on Hybrid Resources(The Eurographics Association and Blackwell Publishing Ltd, 2009) Budge, Brian; Bernardin, Tony; Stuart, Jeff A.; Sengupta, Shubhabrata; Joy, Kenneth I.; Owens, John D.We present a software system that enables path-traced rendering of complex scenes. The system consists of two primary components: an application layer that implements the basic rendering algorithm, and an out-of-core scheduling and data-management layer designed to assist the application layer in exploiting hybrid computational resources (e.g., CPUs and GPUs) simultaneously. We describe the basic system architecture, discuss design decisions of the system s data-management layer, and outline an efficient implementation of a path tracer application, where GPUs perform functions such as ray tracing, shadow tracing, importance-driven light sampling, and surface shading. The use of GPUs speeds up the runtime of these components by factors ranging from two to twenty, resulting in a substantial overall increase in rendering speed. The path tracer scales well with respect to CPUs, GPUs and memory per node as well as scaling with the number of nodes. The result is a system that can render large complex scenes with strong performance and scalability.Item A Precalculated Point Set for Caching Shading Information(The Eurographics Association, 2009) Bikker, Jacco; Reijerse, Roel; P. Alliez and M. MagnorIn this short paper, we present a caching scheme for low-frequent shading information. The scheme consists of a precalculated, carefully constructed sparse set of points, the density of which adapts to local shading requirements, which we estimate by calculating the ambient occlusion. This fixed set of points is then used to store shading information. This shading information is calculated once, or updated prior to rendering each frame. Finally, during rendering, the shading information stored in the point set is used to estimate shading for any point in the scene using interpolation. We apply this scheme to render soft shadows and indirect lighting in a real-time ray traced game environment.Item A Part-aware Surface Metric for Shape Analysis(The Eurographics Association and Blackwell Publishing Ltd, 2009) Liu, Rong; Zhang, Hao; Shamir, Ariel; Cohen-Or, DanielThe notion of parts in a shape plays an important role in many geometry problems, including segmentation, correspondence, recognition, editing, and animation. As the fundamental geometric representation of 3D objects in computer graphics is surface-based, solutions of many such problems utilize a surface metric, a distance function defined over pairs of points on the surface, to assist shape analysis and understanding. The main contribution of our work is to bring together these two fundamental concepts: shape parts and surface metric. Specifically, we develop a surface metric that is part-aware. To encode part information at a point on a shape, we model its volumetric context - called the volumetric shape image (VSI) - inside the shape s enclosed volume, to capture relevant visibility information. We then define the part-aware metric by combining an appropriate VSI distance with geodesic distance and normal variation. We show how the volumetric view on part separation addresses certain limitations of the surface view, which relies on concavity measures over a surface as implied by the well-known minima rule. We demonstrate how the new metric can be effectively utilized in various applications including mesh segmentation, shape registration, part-aware sampling and shape retrieval.Item Importance Sampling Spherical Harmonics(The Eurographics Association and Blackwell Publishing Ltd, 2009) Jarosz, Wojciech; Carr, Nathan A.; Jensen, Henrik WannIn this paper we present the first practical method for importance sampling functions represented as spherical harmonics (SH). Given a spherical probability density function (PDF) represented as a vector of SH coefficients, our method warps an input point set to match the target PDF using hierarchical sample warping. Our approach is efficient and produces high quality sample distributions. As a by-product of the sampling procedure we produce a multi-resolution representation of the density function as either a spherical mip-map or Haar wavelet. By exploiting this implicit conversion we can extend the method to distribute samples according to the product of an SH function with a spherical mip-map or Haar wavelet. This generalization has immediate applicability in rendering, e.g., importance sampling the product of a BRDF and an environment map where the lighting is stored as a single high-resolution wavelet and the BRDF is represented in spherical harmonics. Since spherical harmonics can be efficiently rotated, this product can be computed on-the-fly even if the BRDF is stored in local-space. Our sampling approach generates over 6 million samples per second while significantly reducing precomputation time and storage requirements compared to previous techniques.Item Visualizing Heterogeneous Utility Data: A Case for Aesthetic Design(The Eurographics Association, 2009) Boukhelifa, Nadia; Duke, David; D. Ebert and J. KrügerA map visually enfolds selected messages to a target audience. To achieve this effectively, a clear understanding of 'the message, the user and the purpose' of the map needs to be translated into successful design choices covering content, typography, style and layout. Aesthetics not only inform the local design space over which rules for visual mappings are defined, but they also offer global heuristics to ensure overall visual excellence. In the world of underground utilities where companies use maps to communicate the location of their buried services, personal, internal and sector depiction standards and guidelines have a strong influence on visual design. When the scope of a map, defined by its message, user and purpose' is overlooked, conflicts arise such as between the need for realism and schematisation. In this paper we examine the role aesthetics play in the context of the utility-sector work-flow. We discuss conflicts that arise when the scope of a map's use is not carefully considered. We give details of a case study where we have attempted to reconcile a conflict between accuracy and clarity through a clutter aesthetic. Central to this research is the observed link between data, task and aesthetics; and the question of to what extent can aesthetics be designed and incorporated algorithmically.Item Applications of Multitouch and Gaming Technology for the Classroom(The Eurographics Association, 2009) Muto, William; Dobies, Justin; Diefenbach, Paul; G. Domik and R. ScateniMulti-point touch screens have enjoyed recent popularity due to their natural tendency to create highly intuitive and user-friendly systems for even the novice user. We believe that multitouch is well-suited for educational purposes, since it engages users through an invisible interface and natural, gestural interaction, as well as promoting collaborative learning through equal access, as opposed to individual or "driver and co-pilot" learning at a traditional computer workstation. In this paper, we adopt this powerful interface and combine it with 3D simulation and gaming technology to create a novel teaching tool, incorporating digital learning content co-developed with educators and providing access for administration and student assessment.Item Over Two Decades of Integration-Based, Geometric Flow Visualization(The Eurographics Association, 2009) McLoughlin, Tony; Laramee, Robert S.; Peikert, Ronald; Post, Frits H.; Chen, Min; M. Pauly and G. GreinerFlow visualization is a fascinating sub-branch of scientific visualization. With ever increasing computing power, it is possible to process ever more complex fluid simulations. However, a gap between data set sizes and our ability to visualize them remains. This is especially true for the field of flow visualization which deals with large, timedependent, multivariate simulation datasets. In this paper, geometry based flow visualization techniques form the focus of discussion. Geometric flow visualization methods place discrete objects in the vector field whose characteristics reflect the underlying properties of the flow. A great amount of progress has been made in this field over the last two decades. However, a number of challenges remain, including placement, speed of computation, and perception. In this survey, we review and classify geometric flow visualization literature according to the most important challenges when considering such a visualization, a central theme being the seeding object upon which they are based. This paper details our investigation into these techniques with discussions on their applicability and their relative merits and drawbacks. The result is an up-to-date overview of the current state-of-the-art that highlights both solved and unsolved problems in this rapidly evolving branch of research. It also serves as a concise introduction to the field of flow visualization research.