I work in the
AVIS
lab at
UCSC
and
Alex Pang
is my advisor. We are usually
working very hard except when it's windy and Alex takes off to ride the
waves -- of course I continue to work ;)
I also work closely with
Dr. David Kao
who works for the
data analysis group
at
NASA Ames research center.
My research interests are computer graphics and scientific
visualization.
Following is a quick index to find things fast in this page:
- Research Projects
- Ph.D. Proposal
- Vortex core comparison in flow fields
- Feature based streamline placement
- A texture synthesis technique for flow visualization
- Decimation of tetrahedral grids for direct volume rendering
- Publications
- Presentations
- Poster
RESEARCH PROJECTS
Following is a partial list of my research projects:
Ph.D. PROPOSAL
I advanced to candidacy in June, 1999 and I have proposed research
in the area of comparative visualization. The past decade has witnessed
the emergence of visualization as an inseparable part of data exploration and analysis.
Increase in computing power and advances in computational fluid
dynamics
(CFD) have enabled scientists to have more accurate
models and run simulations that generate huge datasets.
My research is concerned with the study of vector field data defined
over
the discrete locations in three dimensions.
Flow field data is computed using batch jobs on super computers but
visualization demands interactivity.
This demand on visualization has been somewhat of a burden in recent
years and in an effort to use desktop tools for visualization, there
has been a drive to generate visualizations using a simplified
model of the original data.
A simplified model often throws away information that could
be crucial.
Hence, there is a real need to have tools that would help in
understanding the difference in the original and approximated datasets.
The simplest of comparison approaches are image-level and data-level
comparisons.
Image level comparisons use visualization images and image processing
to study the differences in the datasets.
Data-level comparisons use the raw data for comparisons.
Another approach to do comparison is to use feature-level comparisons.
My proposal is to develop methods to compare some of the flow features
commonly extracted from a flow data. I am exploring methods to compare
streamlines, streamribbons, and vorex cores.
A copy of my proposal is available online.
PhD Proposal (UCSC, May 1999)
Color Images
Here are some images from the above work:
Above image: Left image compares two ribbons as an overlay
and the right image compares them by "unfolding" and "flattening"
one of the ribbons and comparing the other w.r.t. the first one.
VORTEX CORE COMPARISON IN FLOW FIELDS
I am currently exploring ways to compare vortex cores that are
extracted from two different datasets. These datasets could be
from wind tunnel experiments or different CFD solvers.
Dataset used: Delta wing (courtesy: Neal Chaderjian, NASA Ames)
FEATURE BASED STREAMLINE PLACEMENT
Streamlines are a popular visualization primitive used to explore
flow fields. One big problem with using streamlines to study flow
fields is that if the streamlines are not placed at proper locations
then they tend to create clutter and can miss important details.
We have developed a method for streamline placement that is guided
by the features in the flow (like critical points) and guarantees that
all the important features will be highlighted by the flow. In addition
our method produces aesthetically pleasing vstreamline visualizations.
This work was done in collaboratin with my advisor Alex Pang and
Dr. David Kao from NASA ames research center.
Above image: A sparse streamline visualization showing five
critical points.
A TEXTURE SYNTHESIS TECHNIQUE FOR FLOW VISUALIZATION
We have developed a method called PLIC (pseudo line integratal
convolution). PLIC can generate visualizations that span the spectrum
of streamline-like to LIC-like. This work was done in collaboratin with
my advisor Alex Pang and Dr. David Kao from NASA ames research center.
Above images: PLIC visualizations of two datasets. Top:
bluntfin; Bottom: dynamc vortices (courtesy: Ravi Samtaney, NASA
Ames)
DECIMATION OF TETRAHEDRAL GRIDS FOR DIRECT VOLUME RENDERING
Often the data generated by CFD simulations is so huge that it's
impossible to visualize it interactively. Tetrahedral grids are very
common in FEM modeling and CFD. As part of work for my Masters degree I
developed a method to decimate tetrahedral grids. The method
iteratively deletes vertices from the grid based on an error metric.
The resulting hole in the grid is patched using a local
re-tetrahedralization. This research was done in collaboration with
Prof. Allen Van Gelder
and
Prof. Jane Wilhelms.
Above images: The image on the left is a direct volume rendering of a dataset
called lftr (langley fighter, courtesy NASA Ames). The image on the
left is rendering using the original grid. For the middle image the
grid was decimated by 80% and for the right image the grid was
decimated by 95%.
Above images: When we decimate the tetrahedral grid, we have to take
special care when we delete vertices from the surface of the grid. We
use a separate error metric for the surface vertices. Note that deleting
vertices from the surface has problems similar to surface decimaiton.
Left image: original surface detail; Middle and Right images: grid
decimated by 80% using two different error metrics for the surface.
Above two images: We also evaluated the quality of the decimated grids
using isosurface extraction algorithms. Top: original grid; Bottom:
grid decimated by 80%.
PUBLICATIONS
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Vivek Verma, David Kao, Alex Pang.
``A Flow-guided Streamline Seeding Strategy''.
Proceedings of IEEE Visualization 2000, Salt Lake City, October 2000.
Vivek Verma, David Kao, Alex Pang.
``PLIC: Bridging the Gap Between Streamlines and LIC''.
Proceedings of IEEE Visualization '99, San Francisco, October
1999.
Allen Van Gelder, Vivek Verma, and Jane Wilhelms.
``Volume Decimation of Irregular Tetrahedral Grids''.
Computer Graphics International, Canada, June 1999.
gzipped paper
Color Images
Vivek Verma and Allen Van Gelder.
``Decimation of Tetrahedral Grids With Error Control''.
UCSC Technical Report number UCSC-CRL-97-25 , June 1998.
Jonathan Gibbs, Allen Van Gelder, Vivek Verma and Jane Wilhelms.
``Rapid Decimation For Direct Volume Rendering''.
UCSC Technical Report number UCSC-CRL-97-26, December 1997.
Vivek Verma.
``Accelerating Convergence of Time Integrating Procedures Using
Recursive Projection Method''.
Masters Thesis, Department of Mathematics, Indian Institute of
Technology, Delhi, May 1994.
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PRESENTATIONS
Slides from IEEE visualization '99 conference in San Francisco
slides from presentation at Vis Lunch (an attempt to use HTML for
presentations)
POSTER
Here is a poster I created for an open house at NASA Ames.
Copyright © 1994-2000
Vivek Verma
All Rights Reserved.
