Recent Advances in VisIt: AMR Streamlines and Query-Driven Visualization Page: 2 of 6
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2 Weber et al.
proven useful in a wide variety of science and engineering application domains,
and visualization researchers have started devoting efforts to the development
of effective visualization and data analysis algorithms for AMR data. Further-
more, AMR support is becoming more common in visualization tools aimed at
a wide user community in science and engineering. One of these tools is VisIt,
which originated at the Lawrence Livermore National Laboratory, and which is
now extended and developed by a larger number of outside groups. The Visual-
ization and Analytics Center for Enabling Technologies (VACET) is working on
extending VisIt with an emphasis of users in the Department of Energy Scien-
tific Discovery through Advanced Computing (SciDAC) program, and improving
VisIt's AMR handling capabilities is an important aspect of this effort.
Recently, our efforts focused on improving VisIt's streamline calculation
algorithms (Section 2.). First, we consider multi-block data sets where blocks
cover disjoint regions of the domain, i.e., blocks that tile the domain and do
not overlap. Originally, VisIt computed streamlines independently within each
block, and streamlines terminated when they reached a block boundary. We
fixed this shortcoming with an implementation that continues streamlines at
block boundaries. A main challenge in this context lies in effective parallelization
and communication strategies.
AMR data poses additional challenges to streamline calculation (Deines et
al. 2009). The domain does not just consist of multiple domains, but these
blocks overlap and are ordered in levels of increasing resolution, where higher
resolution representations of a region in the domain replace lower resolution
versions. Thus, it becomes necessary to take the AMR hierarchy into account
and ensure that interpolation always uses the highest resolution representation
available. Furthermore, one needs to take care when interpolating close to level
Many astrophysical simulations also consider particle data sets consisting
of a large number of particles. Recently, we developed a research prototype (see
Section 3.) that integrates FastBit (Wu, Otoo, & Shoshani 2006) into VisIt, and
the most recent VisIt release includes the functionality of this prototype. It is
possible to perform thresholding operations based on the FastBit index and only
load those particles from disk that are of interest. Furthermore, it is possible
to utilize the index to effectively calculate 2D histograms that can be used for
accelerating parallel coordinate-based visualizations. In the following we survey
these recent developments and provide pointers to papers that describe them in
2. Improving VisIt's Streamline Calculation Capabilities
2.1. Background and Significance
For simulations that involve vector fields, integral curves, or streamlines, are one
of the most illuminating techniques to obtain insight; they are a cornerstone of
visualization and analysis across a great variety of application domains. Drawing
on an intuitive interpretation in terms of particle movement, they are an ideal
tool to illustrate and describe a wide range of phenomena encountered in the
study of application-domain vector fields, such as transport and mixing in fluid
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Weber, Gunther; Ahern, Sean; Bethel, Wes; Borovikov, Sergey; Childs, Hank; Deines, Eduard et al. Recent Advances in VisIt: AMR Streamlines and Query-Driven Visualization, article, November 12, 2009; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc1013741/m1/2/: accessed December 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.