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2009 Workshopband, Fachtagung des GI-Fachbereichs Softwaretechnik, Software Engineering 2009 - 2009 Workshop Conference of the GI Division on Software Engineering, Software Engineering 2009

作者： Fünfzig, Christoph Müller, Kerstin Albrecht, Gudrun LE2I-MGSI UMR CNRS 5158 Université de Bourgogne France Computer Graphics and Visualization TU Kaiserslautern Germany LAMAV FR CNRS 2956 Université de Valenciennes et du Hainaut-Cambrésis France

ISBN: (纸本)9783885792444

Haptic applications are difficult to debug due to their high update rate and many factors influencing their execution. In this paper, we describe a practical visual debugger for single-point-of-contact haptic devices of impedance-type. The debugger can easily be incorporated into the running haptic application. The visualization shows the position trajectory with timing information and associated data like goal positions and computed feedback forces. Also, there are several options for in detail analysis of the feedback force applied at each time instance. We show with several use cases taken from practical experience that the system is well suited for locating common and intricate problems of haptic applications. © 2009 Gesellschaft fur Informatik (GI). All rights reserved.

关键词： Point contacts

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Automated 3D heart segmentation by search rays for building individual conductor models

Automated 3D heart segmentation by search rays for building ...

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Medical Imaging 2009: visualization, Image-Guided Procedures, and Modeling

作者： Kim, Jaeil Kim, Seokyeol Kim, Kiwoong Park, Jinah Computer Graphics and Visualization Laboratory Information and Communications University 119 Munji-ro Yusung-gu Daejeon Korea Republic of Center for Brain and Cognitive Science Research Korea Research Institute of Standards and Science 209 Gajung-ro Yusung-gu Daejeon Korea Republic of

ISBN: (纸本)9780819475121

Magnetocardiograph (MCG) is one of the most useful diagnosing tools for myocardial ischemic diseases and the conduction abnormality, since the technique directly measures magnetic fields generated by myocardial currents without distortion in a non-invasive way. To localize the current source accurately, building a patient-specific conductor model is indispensable. In this paper, we present the method to automatically construct a patient-specific three-dimensional (3D) mesh model of a human thorax and a heart consisting of pericardium and four chambers. We represent the standard thorax model by simplex meshes, and deform them to fit into the individual CT data to reconstruct accurate surface representations for the MCG conductor model. The deformable simplex mesh model deforms based on the external forces exerted by the edge and gradient components of the source volume data while its internal force acts to maintain the integrity of the shape. However, image driven deformation is often very sensitive to its initial position. Therefore, we suggest our solution to automatic region-of-interest (ROI) detection using search rays, which are casted to 3D volume images to identify the region of a heart based on both the radiodensity values and their continuity along the path of the rays. Upon automatic ROI detection with search rays, the initial position and orientation of the standard mesh model is determined, and each vertex of the model is respectively moved by the weighted sum of the internal and eternal forces to conform to the each patient's own thorax and heart shape while minimizing the user's input. © 2009 SPIE.

关键词： Heart

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Interpolating and downsampling RGBA volume data

Interpolating and downsampling RGBA volume data

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13th International Fall Workshop Vision, Modeling, and visualization 2008, VMV 2008

作者： Kraus, Martin Bürger, Kai Computer Graphics and Visualization Group Technische Universität München Germany

ISBN: (纸本)9781586039219

For about twenty years the standard color sampling method for RGBA volume data has been the interpolation of opacity-weighted colors. In this work, we discuss the underlying approximations and derive an improved sampling method, which avoids some of these approximations. With the help of several examples and experiments we demonstrate that our new technique is in fact preferable for direct volume rendering of RGBA data. Moreover, we show that the same improvement can be applied to downsampling filters. Finally, we propose a procedure to design improved downsampling filters for the generation of pyramid RGBA volume data such as mipmap volume textures.

关键词： Interpolation

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Corotated finite elements made fast and stable

Corotated finite elements made fast and stable

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5th Workshop on Virtual Reality Interactions and Physical Simulations, VRIPHYS 2008

作者： Georgii, Joachim Westermann, Rüdiger Computer Graphics and Visualization Group Technische Universität München Germany

ISBN: (纸本)9783905673708

Multigrid finite-element solvers using the corotational formulation of finite elements provide an attractive means for the simulation of deformable bodies exhibiting linear elastic response. The separation of rigid body motions from the total element motions using purely geometric methods or polar decomposition of the deformation gradient, however, can introduce instabilities for large element rotations and deformations. Furthermore, the integration of the corotational formulation into dynamic multigrid elasticity simulations requires to continually rebuild consistent system matrices at different resolution levels. The computational load imposed by these updates prohibits the use of large numbers of finite elements at rates comparable to the small-strain finite element formulation. To overcome the first problem, we present a new method to extract the rigid body motion from total finite element displacements based on energy minimization. This results in a very stable corotational formulation that only slightly increases the computational overhead. We address the second problem by introducing a novel algorithm for computing sparse products of the form RKRT, as they have to be evaluated to update the multigrid hierarchy. By reformulating the problem into the simultaneous processing of a sequential data and control stream, cache miss penalties are significantly reduced. Even though the algorithm increases memory requirements, it accelerates the multigrid FE simulation by a factor of up to 4 compared to previous multigrid approaches. Due to the proposed improvements, finite element deformable body simulations using the corotational formulation can be performed at rates of 17 tps for up to 12k elements. © The Eurographics Association 2008.

关键词： Deformation

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Pre-integrated volume rendering for multi-dimensional transfer functions

Pre-integrated volume rendering for multi-dimensional transf...

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Joint IEEE/EG 7th International Symposium on Volume graphics, VG 2008 and 5th Symposium on Point-Based graphics, PBG 2008

作者： Kraus, M. Computer Graphics and Visualization Group Technische Universität München Germany

ISBN: (纸本)9783905674125

This work presents an efficient extension of pre-integrated volume rendering for multi-dimensional transfer functions. Since even two-dimensional transfer functions can result in strong rendering artifacts that cannot be resolved by standard ray casting, we propose a space-covering volume sampling scheme that does not require additional samples of the volume data. Based on this sampling scheme, our approach computes box integrals of the transfer functions, which are evaluated with the help of a small number of texture lookups in tabulated integral functions. We demonstrate the achieved performance and improvements in image quality with a prototypical GPU (graphics processing unit) implementation. © The Eurographics Association 2008.

关键词： Transfer functions

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Delocalized unsteady vortex region detectors

Delocalized unsteady vortex region detectors

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13th International Fall Workshop Vision, Modeling, and visualization 2008, VMV 2008

作者： Fuchs, Raphael Peikert, Ronald Sadlo, Filip Alsallakh, Bilal Gröller, Meister Eduard Institute of Computer Graphics and Algorithms TU Vienna Austria VRVis Research Center for Virtual Reality and Visualization Vienna Austria Computer Graphics Laboratory ETH Zurich Switzerland

ISBN: (纸本)9781586039219

In this paper we discuss generalizations of instantaneous, local vortex criteria. We incorporate information on spatial context and temporal development into the detection process. The presented method is generic in so far that it can extend any given Eulerian criterion to take the Lagrangian approach into account. Furthermore, we present a visual aid to understand and steer the feature extraction process. We show that the delocalized detectors are able to distinguish between connected vortices and help understanding regions of multiple interacting vortex structures. The delocalized detectors extract smoother structures and reduce noise in the vortex detection result.

关键词： Vortex flow

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A User Guidance Approach for Passive Haptic Environments 14

A User Guidance Approach for Passive Haptic Environments

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14th Eurographics Symposium on Virtual Environments, EGVE 2008

作者： Steinicke, F. Welzel, H. Bruder, G. Hinrichs, K. Visualization and Computer Graphics Research Group Institute of Computer Science Westfälische Wilhelms-Universität Münster Germany

ISBN: (纸本)9783905673661

Traveling through virtual environments (VEs) by means of real walking is a challenging task since usually the size of the virtual world exceeds the size of the tracked interaction space. Redirected walking is one concept to solve this problem by guiding the user on a physical path which differs from the path the user visually perceives, for example, in head-mounted display (HMD) *** user can be redirected to certain locations in the physical space, in particular to real proxy objects which provide passive feedback. In such passive haptic environments, any number of virtual objects can be mapped to proxy objects having similar haptic properties, i. e., size, shape and texture. When the user is guided to corresponding proxy objects, s/he can sense virtual objects by touching their real world counterparts. Therefore it is vital to predict the user’s movements in the virtual world in order to recognize the target location. Based on the prediction a transformed path can be determined in the physical space on which the user is guided to the desired proxy object. In this paper we present concepts how a user’s path can be predicted reliably and how a corresponding path to a desired proxy object can be derived on which the user does not observe inconsistencies between vision and proprioception. © The Eurographics Association 2008.

关键词： Virtual reality

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PNG1 triangles for tangent plane continuous surfaces on the GPU

PNG1 triangles for tangent plane continuous surfaces on the ...

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graphics Interface 2008

作者： Fünfzig, Christoph Müller, Kerstin Hansford, Dianne Farin, Gerald PRISM Lab Arizona State University Tempe United States Computer Graphics and Visualization University Kaiserslautern Germany

ISBN: (纸本)9781568814230

Improving the visual appearance of coarse triangle meshes is usually done with graphics hardware with per-pixel shading techniques. Improving the appearance at silhouettes is inherently hard, as shading has only a small influence there and the geometry must be corrected. With the new geometry shader stage released with DirectX 10, the functionality to generate new primitives from an input primitive is available. Also the shader can access a restricted primitive neighborhood. In this paper, we present a curved surface patch that can deal with this restricted data available in the geometry shader. A surface patch is defined over a triangle with its vertex normals and the three edge neighbor triangles. Compared to PN triangles, which define a curved patch using just the triangle with its vertex normals, our surface patch is G1 continuous with its three neighboring patches. The patch is obtained by blending two cubic Bézier patches for each triangle edge. In this way, our surface is especially suitable for efficient, high-quality tessellation on the GPU. We show the construction of the surface and how to add special features such as creases. Thus, the appearance of the surface patch can be fine-tuned easily. The surface patch is easy to integrate into existing polygonal modeling and rendering environments. We give some examples using Autodesk Maya.

关键词： graphics processing unit

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A versatile hierarchical mesh for subdivision surfaces

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IEEE Potentials 2008年第5期27卷 20-25页

作者： Fünfzig, Christoph Müller, Kerstin Janetzek, Rafael Techmann, Torsten PRISM Lab. Arizona State University United States PRISM Lab. Arizona State University Computer Graphics and Visualization University of Kaiserslautern Germany Darmstadt University of Technology Germany

The construction and processing of surface geometry can be done by connecting surface primitives to vertices, edges, and neighbors. The representation schemes of surface geometry are vertex-based, edge-based, and quad-edge-based. Catmull and Clark rule of subdivision includes three different rules to create new vertices in the refined control mesh, that are vertex, edge, and face subdivision rule. A new vertex can be created in the refined mesh as a convex combination of the vertices in the neighborhood of vertex, edge, and face in the control mesh. The first subdivision step has a quadrangle control mesh and number of vertices with valence unequal to four constant during refinement. The Charles Loop subdivision scheme is based on box spline and during a subdivision a triangle is divided into four triangles through vertex and edge subdivision rule.

关键词： Mesh generation

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Noisevis3D: A framework for interactive 3D traffic noise visualization

Noisevis3D: A framework for interactive 3D traffic noise vis...

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computer graphics and visualization 2008 and Gaming 2008: Design for Engaging Experience and Social Interaction 2008, MCCSIS'08 - IADIS Multi Conference on computer Science and Information Systems

作者： Michel, Frank Wacker, Petra Strupp, Samuel Hagen, Hans IRTG 1131 Department of Computer Science University of Kaiserslautern 67663 Kaiserslautern Germany Computer Graphics and Visualization Department of Computer Science University of Kaiserslautern 67663 Kaiserslautern Germany

ISBN: (纸本)9789728924638

We present NoiseVis3D a framework for the interactive three dimensional visualization of traffic noise. The framework allows the visualization of noise maps in new ways including multilayer 2D maps, volume rendering of noise and isosurfaces besides the usual visualization of 2D noise maps. The three dimensional visualization allows the users to explore the virtual city model and immerse themselves in the current sound situation. The possibility to integrate additional information into the model enables the illustration not only of noise exposure but also vital information for decision makers, investors and local residents. © 2008 IADIS.

关键词： visualization

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