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ieee visualization Conference (Vis 2006)/ieee symposium on Information visualization (InfoVis 2006)

作者： Lindstrom, Peter Isenburg, Martin Lawrence Livermore Natl Lab Livermore CA 94551 USA Univ Calif Berkeley Berkeley CA 94720 USA

large scale scientific simulation codes typically run on a cluster of CPUs that write/read time steps to/from a single file system. As data sets are constantly growing in size, this increasingly leads to I/O bottlenecks. When the rate at which data is produced exceeds the available I/O bandwidth, the simulation stalls and the CPUs are idle. data compression can alleviate this problem by using some CPU cycles to reduce the amount of data needed to be transfered. Most compression schemes, however, are designed to operate offline and seek to maximize compression, not throughput. Furthermore, they often require quantizing floating-point values onto a uniform integer grid, which disqualifies their use in applications where exact values must be retained. We propose a simple scheme for lossless, online compression of floating-point data that transparently integrates into the I/O of many applications. A plug-in scheme for data-dependent prediction makes our scheme applicable to a wide variety of data used in visualization, such as unstructured meshes, point sets, images, and voxel grids. We achieve state-of-the-art compression rates and speeds, the latter in part due to an improved entropy coder. We demonstrate that this significantly accelerates I/O throughput in real simulation runs. Unlike previous schemes, our method also adapts well to variable-precision floating-point and integer data.

关键词： high throughput lossless compression file compaction for I/O efficiency fast entropy coding range coder predictive coding large scale simulation and visualization

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LOD map - A visual interface for navigating multiresolution volume visualization

LOD map - A visual interface for navigating multiresolution ...

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ieee visualization Conference (Vis 2006)/ieee symposium on Information visualization (InfoVis 2006)

作者： Wang, Chaoli Shen, Han-Wei Ohio State Univ Dept Comp Sci & Engn Columbus OH 43210 USA

In multiresolution volume visualization, a visual representation of level-of-detail (LOD) quality is important for us to examine, compare, and validate different LOD selection algorithms. While traditional methods rely on ultimate images for quality measurement, we introduce the LOD map - an alternative representation of LOD quality and a visual interface for navigating multiresolution data exploration. Our measure for LOD quality is based on the formulation of entropy from information theory. The measure takes into account the distortion and contribution of multiresolution data blocks. A LOD map is generated through the mapping of key LOD ingredients to a treemap representation. The ordered treemap layout is used for relative stable update of the LOD map when the view or LOD changes. This visual interface not only indicates the quality of LODs in an intuitive way, but also provides immediate suggestions for possible LOD improvement through visually-striking features. It also allows us to compare different views and perform rendering budget control. A set of interactive techniques is proposed to make the LOD adjustment a simple and easy task. We demonstrate the effectiveness and efficiency of our approach on large scientific and medical data sets.

关键词： LOD map knowledge representation perceptual reasoning multiresolution rendering large volume visualization

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Visual exploration of complex time-varying graphs

Visual exploration of complex time-varying graphs

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ieee visualization Conference (Vis 2006)/ieee symposium on Information visualization (InfoVis 2006)

作者： Kumar, Gautam Garland, Michael Univ Illinois Urbana IL 61801 USA

Many graph drawing and visualization algorithms, such as force-directed layout and line-dot rendering, work very well on relatively small and sparse graphs. However, they often produce extremely tangled results and exhibit impractical running times for highly non-planar graphs with large edge density. And very few graph layout algorithms support dynamic time-varying graphs;applying them independently to each frame produces distracting temporally incoherent visualizations. We have developed a new visualization technique based on a novel approach to hierarchically structuring dense graphs via stratification. Using this structure, we formulate a hierarchical force-directed layout algorithm that is both efficient and produces quality graph layouts. The stratification of the graph also allows us to present views of the data that abstract away many small details of its structure. Rather than displaying all edges and nodes at once, resulting in a convoluted rendering, we present an interactive tool that filters edges and nodes using the graph hierarchy and allows users to drill down into the graph for details. Our layout algorithm also accommodates time-varying graphs in a natural way, producing a temporally coherent animation that can be used to analyze and extract trends from dynamic graph data. For example, we demonstrate the use of our method to explore financial correlation data for the U.S. stock market in the period from 1990 to 2005. The user can easily analyze the time-varying correlation graph of the market, uncovering information such as market sector trends, representative stocks for portfolio construction, and the interrelationship of stocks over time.

关键词： graph and network visualization financial data visualization hierarchy visualization time series data

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visualization aspects in the MERCW project

Visualization aspects in the MERCW project

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ieee US/EU Baltic International symposium, BALTIC 2006

作者： Borodin, P. Greß, A. Klein, R. University of Bonn Institute of Computer Science II Römerstraße 164 Bonn53117 Germany

ISBN: (纸本)9781509002122

The MERCW project focuses on the study of chemical munition dump sites in the Baltic Sea and Skagerrak area. Through focused site investigations an assessment will be made of the ecological risks related to the dumped warfare for the marine ecosystem and people. One of the objectives of the project is to illustrate the results from the risk assessment using innovative visualization techniques. Our aim is to develop technology to interactively analyze and explore data that is collected, simulated, and used in the project, in order to support decision-making, risk analysis, and emergency plans. The data to be considered will include detailed bathymetric maps of the sea bottom, different scalar fields defined on the 3D water volume (e.g. temperature, salinity, and concentrations of poisonous substances) as well as vector fields (e.g. sea currents). In order to achieve this goal we will apply and enhance well-established methods of terrain, volume, and flow visualization. Special emphasis will be put on fast techniques that exploit the parallel computing power of current graphics processing units (GPUs). In addition to common visualization techniques, stereo rendering in virtual environments, such as PowerWall and CAVE, will further enhance the perception and understanding of complex 3D phenomena. © 2006 ieee.

关键词： Risk assessment

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Interactive visualization of intercluster galaxy structures in the horologium-reticulum supercluster

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ieee TRANSACTIONS ON visualization AND COMPUTER graphics 2006年第5期12卷 1149-1155页

作者： Miller, Jameson Quammen, Cory W. Fleenor, Matthew C. Univ N Carolina Dept Comp Sci Chapel Hill NC 27599 USA Roanoke Coll Dept Math Comp Sci & Phys Salem VA 24153 USA

We present GyVe, an interactive visualization tool for understanding structure in sparse three-dimensional (3D) point data. The scientific goal driving the tool's development is to determine the presence of filaments and voids as defined by inferred 3D galaxy positions within the Horologium-Reticulum supercluster (HRS). GyVe provides visualization techniques tailored to examine structures defined by the intercluster galaxies. Specific techniques include: interactive user control to move between a global overview and local viewpoints, labelled axes and curved drop lines to indicate positions in the astronomical RA-DEC-cz coordinate system, torsional rocking and stereo to enhance 3D perception, and geometrically distinct glyphs to show potential correlation between intercluster galaxies and known clusters. We discuss the rationale for each design decision and review the success of the techniques in accomplishing the scientific goals. In practice, GyVe has been useful for gaining intuition about structures that were difficult to perceive with 2D projection techniques alone. For example, during their initial session with GyVe, our collaborators quickly confirmed scientific conclusions regarding the large-scale structure of the HRS previously obtained over months of study with 2D projections and statistical techniques. Further use of GyVe revealed the spherical shape of voids and showed that a presumed filament was actually two disconnected structures.

关键词： sparse point visualization astronomy cosmology

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Distributed physical based simulations for large VR applications

Distributed physical based simulations for large VR applicat...

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ieee Virtual Reality 2006 Conference

作者： Allard, Jeremie Raffin, Bruno INPG INRIA UJF CNRSID IMAG Grenoble France

ISBN: (纸本)1424402239

We present a novel software framework for developing highly animated virtual reality applications. Using a modular application design, our goal is to alleviate software engineering issues while yielding efficient execution on parallel machines. We target worlds involving numerous animated objects managed by physical based simulations. Mixing rigid objects, fluids, mass-spring or other deformable objects leads to complex interactions between them. Today no unified simulation algorithm with a reasonable complexity is available to manage all these types of objects. We propose a framework for coupling and distributing existing algorithms. We reuse and extend the data-flow model where an application is built from modules exchanging data through connections. The model relies on two main classes of modules, animators and interactors. Animators are responsible for updating objects' states from forces applied to them. These forces are computed in parallel by interactors using the objects' states they receive from animators. The network interconnecting modules can be progressively optimized. From a simple fully connected network enforcing a synchronous semantics, it can evolve towards an active network able to implement a bounding volume based dynamic routing or an asynchronous data re-sampling. As a result, we present an application managing interactions between rigid objects, mass-spring objects and a fluid. It is executed in real-time on a 54 processors cluster driving 5 cameras and 16 projectors for user interactions.

关键词： virtual reality animations interactions physical based simulation coupling distributed and parallel graphics applications modular programming graphics clusters

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Interactive volume rendering of unstructured grids with time-varying scalar fields

Interactive volume rendering of unstructured grids with time...

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6th Eurographics symposium on parallel graphics and visualization, EGPGV 2006

作者： Bernardon, Fábio F. Callahan, Steven P. Comba, João L.D. Silva, Cláudio T. Instituto de Informática Federal University of Rio Grande do Sul Brazil Scientific Computing and Imaging Institute University of Utah United States

ISBN: (纸本)3905673401

Interactive visualization of time-varying volume data is essential for many scientific simulations. This is a challenging problem since this data is often large, can be organized in different formats (regular or irregular grids), with variable instances of time (from few hundreds to thousands) and variable domain fields. It is common to consider subsets of this problem, such as time-varying scalar fields (TVSFs) on static structured grids, which are suitable for compression using multi-resolution techniques and can be efficiently rendered using texture-mapping hardware. In this work we propose a rendering system that considers unstructured grids, which do not have the same regular properties crucial to compression and rendering. Our solution uses an encoding mechanism that is tightly coupled with our rendering system. Decompression is performed on the CPU while rendering for the next frame is processed. The rendering system runs entirely on the GPU, with an adaptive time-varying visualization that has a built-in level-of-detail that chooses the most significant aspects of the data. © The Eurographics Association 2006.

关键词： visualization

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Design for parallel interactive ray tracing systems

Design for parallel interactive ray tracing systems

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ieee symposium on Interactive Ray Tracing 2006

作者： Bigler, James Stephens, Abe Parker, Steven G. Univ Utah Sci Comp & Imaging Inst Salt Lake City UT 84112 USA

ISBN: (纸本)9781424406937

We describe the software architecture of the Manta interactive ray tracer and describe its application in engineering and scientific visualization. Although numerous ray tracing software packages have been developed, much of the traditional design wisdom needs to be updated to provide support for interactivity, high degrees of parallelism, and modem packet-based acceleration structures. We discuss situations that are normally not considered when designing a batch ray tracer, and present methods to overcome those challenges. This paper advocates a forward looking programming model for interactive ray tracing that uses reconfigurable components to achieve flexibility while achieving scalability on large numbers of processors. Manta employs data structures motivated by modem micro-processor design that can exploit instruction-level parallelism. We discuss the design tradeoffs and the performance achieved for this system.

关键词： ray tracing interactive ray tracing software architecture

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Time step prioritising in parallel feature extraction on unsteady simulation data

Time step prioritising in parallel feature extraction on uns...

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6th Eurographics symposium on parallel graphics and visualization, EGPGV 2006

作者： Wolter, M. Hentschel, B. Schirski, M. Gerndt, A. Kuhlen, T. Virtual Reality Group RWTH Aachen University Germany

ISBN: (纸本)3905673401

Explorative analysis of unsteady computational fluid dynamics (CFD) simulations requires a fast extraction of flow features. For time-varying data, the extraction algorithm has to be executed for each time step in the period under observation. Even when parallelised on a remote high performance computer, the user’s waiting time still exceeds interactivity criteria for large data sets. Moreover, computations are generally performed in a fixed order, not taking into account the importance of partial results for the user’s investigation. In this paper we propose a general method to guide parallel feature extraction on unsteady data sets in order to assist the user during the explorative analysis even though interactive response times might not be available. By re-ordering of single time step computations, the order in which features are provided is arranged according to the user’s exploration process. We describe three different concepts based on typical user behaviours. Using this approach, parallel extraction of unsteady features is enhanced for arbitrary extraction methods. © The Eurographics Association 2006.

关键词： Feature extraction

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Hierarchical parallel processing of large scale data clustering on a PC cluster with GPU co-processing

Hierarchical parallel processing of large scale data cluster...

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2nd International symposium on parallel and Distributed Processing and Applications (ISPA 2004)

作者： Takizawa, Hiroyuki Kobayashi, Hiroaki Tohoku Univ Grad Sch Informat Sci Aoba Ku Sendai Miyagi 9808578 Japan Tohoku Univ Informat Synergy Ctr Aoba Ku Sendai Miyagi 9808578 Japan

This paper presents an effective scheme for clustering a huge data set using a PC cluster system, in which each PC is equipped with a commodity programmable graphics processing unit (GPU). The proposed scheme is devised to achieve three-level hierarchical parallel processing of massive data clustering. The divide-and-conquer approach to parallel data clustering is employed to perform the coarse-grain parallel processing by multiple PCs with a message passing mechanism. By taking advantage of the GPU's parallel processing capability, moreover, the proposed scheme can exploit two types of the fine-grain data parallelism at the different levels in the nearest neighbor search, which is the most computationally-intensive part of the data-clustering process. The performance of our scheme is discussed in comparison with that of the implementation entirely running on CPU. Experimental results clearly show that the proposed hierarchial parallel processing can remarkably accelerate the data clustering task. Especially, GPU co-processing is quite effective to improve the computational efficiency of parallel data clustering on a PC cluster. Although data-transfer from GPU to CPU is generally costly, acceleration by GPU co-processing is significant to save the total execution time of data-clustering.

关键词： programmable graphics processing unit (GPU) general-purpose computation on GPU (GPGPU) k-means data clustering PC cluster the divide-and-conquer approach

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