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Load-Balanced Parallel Streamline Generation on Large Scale vector fields

IEEE TRANSACTIONS ON visualization ANd COMPUTER GRAPHICS 2011年第12期17卷 1785-1794页

作者： Nouanesengsy, Boonthanome Lee, Teng-Yok Shen, Han-Wei Ohio State Univ Columbus OH 43210 USA

Because of the ever increasing size of output data from scientific simulations, supercomputers are increasingly relied upon to generate visualizations. One use of supercomputers is to generate field lines from large scale flow fields. When generating field lines in parallel, the vector field is generally decomposed into blocks, which are then assigned to processors. Since various regions of the vector field can have different flow complexity, processors will require varying amounts of computation time to trace their particles, causing load imbalance, and thus limiting the performance speedup. To achieve load-balanced streamline generation, we propose a workload-aware partitioning algorithm to decompose the vector field into partitions with near equal workloads. Since actual workloads are unknown beforehand, we propose a workload estimation algorithm to predict the workload in the local vector field. A graph-based representation of the vector field is employed to generate these estimates. Once the workloads have been estimated, our partitioning algorithm is hierarchically applied to distribute the workload to all partitions. We examine the performance of our workload estimation and workload-aware partitioning algorithm in several timings studies, which demonstrates that by employing these methods, better scalability can be achieved with little overhead.

关键词： Flow visualization Parallel processing 3d vector field visualization Streamlines

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Efficient computation and visualization of coherent structures in fluid flow applications

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IEEE TRANSACTIONS ON visualization ANd COMPUTER GRAPHICS 2007年第6期13卷 1464-1471页

作者： Garth, Christoph Gerhardt, Florian Tricoche, Xavier Hagen, Hans Univ Kaiserslautern D-67663 Kaiserslautern Germany Univ Calif Davis Inst Data Anal & Visualizat Davis CA 95616 USA Univ Utah SCI Inst Salt Lake City UT 84112 USA Purdue Univ W Lafayette IN 47907 USA

The recently introduced notion of Finite-Time Lyapunov Exponent to characterize Coherent Lagrangian Structures provides a powerful framework for the visualization and analysis of complex technical flows. Its definition is simple and intuitive, and it has a deep theoretical foundation. While the application of this approach seems straightforward in theory, the associated computational cost is essentially prohibitive. due to the Lagrangian nature of this technique, a huge number of particle paths must be computed to fill the space-time flow domain. In this paper, we propose a novel scheme for the adaptive computation of FTLE fields in two and three dimensions that significantly reduces the number of required particle paths. Furthermore, for three-dimensional flows, we show on several examples that meaningful results can be obtained by restricting the analysis to a well-chosen plane intersecting the flow domain. Finally, we examine some of the visualization aspects of FTLE-based methods and introduce several new variations that help in the analysis of specific aspects of a flow.

关键词： flow visualization feature detection 3d vector field visualization

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A graphics hardware-based vortex detection and visualization system 04

A graphics hardware-based vortex detection and visualization...

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IEEE visualization 2004 Conference

作者： Stegmaier, S Ertl, T Univ Stuttgart Inst Visualizat & Interact Syst Stuttgart Germany

ISBN: (纸本)0780387880

Feature detection in flow fields is a well researched area, but practical application is often difficult due to the numerical complexity of the algorithms preventing interactive use and due to noise in experimental or high-resolution simulation data sets. We present an integrated system that provides interactive denoising, vortex detection, and visualization of vector data on Cartesian grids. All three major phases are implemented in such a way that the system runs completely on a modem GPU once the vector field is downloaded into graphics memory. The application aspect of our paper is twofold. First, we show how recently presented, prototypical GPU-based algorithms for filtering numerical computation, and volume rendering can be combined into one productive system by handling all idiosyncrasies of a chosen graphics card. Second, we demonstrate that the significant speedup achieved compared to an optimized software implementation now allows interactive exploration of characteristic structures in turbulent flow fields.

关键词： features in volume data sets flow visualization hardware acceleration 3d vector field visualization

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Opening the can of worms: An exploration tool for vortical flows

Opening the can of worms: An exploration tool for vortical f...

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IEEE visualization 2005 Conference

作者： Stegmaier, S Rist, U Ertl, T Institute for Visualization and Interactive Systems University of Stuttgart Germany Institute for Aerodynamics and Gasdynamics University of Stuttgart Germany

ISBN: (纸本)0780394623

Gaining a comprehensive understanding of turbulent flows still poses one of the great challenges in fluid dynamics. A well-established approach to advance this research is the analysis of the vortex structures contained in the flow. In order to be able to perform this analysis efficiently, supporting visualization tools with clearly defined requirements are needed. In this paper, we present a visualization system which matches these requirements to a large extent. The system consists of two components. The first component analyzes the flow by means of a novel combination of vortex core line detection and the lambda(2) method. The second component is a vortex browser which allows for an interactive exploration and manipulation of the vortices detected and separated during the first phase. Our system improves the reliability and applicability of existing vortex detection methods and allows for a more efficient study of vortical flows which is demonstrated in an evaluation performed by experts.

关键词： flow features vortex detection interactive manipulation 3d vector field visualization

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Time and Streak Surfaces for Flow visualization in Large Time-Varying data Sets

Time and Streak Surfaces for Flow Visualization in Large Tim...

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IEEE Information visualization Conference/IEEE visualization Conference

作者： Krishnan, Hari Garth, Christoph Joy, Kenneth I. Univ Calif Davis Inst Data Anal & Visualizat Davis CA 95616 USA

Time and streak surfaces are ideal tools to illustrate time-varying vector fields since they directly appeal to the intuition about coherently moving particles. However, efficient generation of high-quality time and streak surfaces for complex, large and time-varying vector field data has been elusive due to the computational effort involved. In this work, we propose a novel algorithm for computing such surfaces. Our approach is based on a decoupling of surface advection and surface adaptation and yields improved efficiency over other surface tracking methods, and allows us to leverage inherent parallelization opportunities in the surface advection, resulting in more rapid parallel computation. Moreover, we obtain as a result of our algorithm the entire evolution of a time or streak surface in a compact representation, allowing for interactive, high-quality rendering, visualization and exploration of the evolving surface. Finally, we discuss a number of ways to improve surface depiction through advanced rendering and texturing, while preserving interactivity, and provide a number of examples for real-world datasets and analyze the behavior of our algorithm on them.

关键词： 3d vector field visualization flow visualization time-varying time and streak surfaces surface extraction

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Eyelet particle tracing - Steady visualization of unsteady flow

Eyelet particle tracing - Steady visualization of unsteady f...

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IEEE visualization 2005 Conference

作者： Wiebel, A Scheuermann, G Univ Leipzig Image & Signal Proc Grp Dept Comp Sci D-7010 Leipzig Germany

ISBN: (纸本)0780394623

It is a challenging task to visualize the behavior of time-dependent 3d vector fields. Most of the time an overview of unsteady fields is provided via animations, but, unfortunately, animations provide only transient impressions of momentary flow. In this paper we present two approaches to visualize time varying fields with fixed geometry. Path lines and streak lines represent such a steady visualization of unsteady vector fields, but because of occlusion and visual clutter it is useless to draw them all over the spatial domain. A selection is needed. We show how bundles of streak lines and path lines, running at different times through one point in space, like through an eyelet, yield an insightful visualization of flow structure ("eyelet lines"). To provide a more intuitive and appealing visualization we also explain how to construct a surface from these lines. As second approach, we use a simple measurement of local changes of a field over time to determine regions with strong changes. We visualize these regions with isosurfaces to give an overview of the activity in the dataset. Finally we use the regions as a guide for placing eyelets.

关键词： 3d vector field visualization time-varying data visualization flow visualization vector/tensor visualization

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Generation of Accurate Integral Surfaces in Time-dependent vector fields

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IEEE TRANSACTIONS ON visualization ANd COMPUTER GRAPHICS 2008年第6期14卷 1404-1411页

作者： Garth, Christoph Krishnan, Hari Tricoche, Xavier Bobach, Tom Joy, Kenneth I. Univ Calif Davis Inst Data Anal & Visualizat Davis CA 95616 USA Purdue Univ Dept Comp Sci W Lafayette IN 47907 USA Univ Kaiserslautern Geometr Algorithms Grp D-67663 Kaiserslautern Germany

We present a novel approach for the direct computation of integral surfaces in time-dependent vector fields. As opposed to previous work, which we analyze in detail, our approach is based on a separation of integral surface computation into two stages: surface approximation and generation of a graphical representation. This allows us to overcome several limitations of existing techniques. We first describe an algorithm for surface integration that approximates a series of time lines using iterative refinement and computes a skeleton of the integral surface. In a second step, we generate a well-conditioned triangulation. Our approach allows a highly accurate treatment of very large time-varying vector fields in an efficient, streaming fashion. We examine the properties of the presented methods on several example datasets and perform a numerical study of its correctness and accuracy. Finally, we investigate some visualization aspects of integral surfaces.

关键词： 3d vector field visualization flow visualization time-varying and time-series visualization surface extraction

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Time and Streak Surfaces for Flow visualization in Large Time-Varying data Sets

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IEEE TRANSACTIONS ON visualization ANd COMPUTER GRAPHICS 2009年第6期15卷 1267-1274页

作者： Krishnan, Hari Garth, Christoph Joy, Kenneth I. Univ Calif Davis Inst Data Anal & Visualizat Davis CA 95616 USA

关键词： 3d vector field visualization flow visualization time-varying time and streak surfaces surface extraction

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