# VisLunch/Fall2009

### From VisTrailsWiki

## December 11, 2009

- **Photo-based Industrial Augmented Reality Registration And Navigation Methods**

This talk will briefly introduce an industrial project for discrepancy check using augmented reality. Construction companies employ CAD software during the planning phase. Unfortunately what is finally built often does not match the original plan. The procedure of validating the model is called "discrepancy check". The system proposed here allows the user to easily obtain an augmentation in order to find differences between the planned 3D model and the built items. The main difference to previous body of work in this field is the emphasis on usability and acceptance of the solution. We will demonstrates some user interaction techniques that ease the navigation in the augmented CAD documentation and briefly present the different algorithms developed to registered still images to a CAD coordinates systems. The talk will also describe a registration approach based on keyframe. Registration is at the core of every photo-based AR software such as ours. This alignment of the image to the 3D model coordinate system is usually achieved with fiducial markers. When a single keyframe is used, the unknown baseline length has to be estimated in order to superimpose virtual models onto the image. In this present, I will present an automatic algorithm to augment the relative pose, estimated using a single keyframe, into a full pose that will permit superimposition.

- *Speaker:* Pierre Georgel (Technical University of Munich), http://campar.in.tum.de/Main/PierreGeorgel

- *Where:* Conference Room 3760

- *When:* Friday 10am (12/11)

## November 20, 2009

- **Bubble Sets: Revealing Set Relations with Isocontours over Existing Visualizations** (VIS paper discussion)

- *Speaker:* Dave Koop (SCI), http://www.sci.utah.edu/people/dakoop.html

- *Where:* Conference Room 3760

- *When:* Friday noon (11/20)

## November 13, 2009

- **Ensemble-Vis: A Framework for the Statistical Visualization of Ensemble Data**

Scientists are increasingly using "ensemble data sets" to explore relationships present in dynamic systems. Ensemble data sets combine spatio-temporal simulation results generated using multiple numerical models, sampled input conditions and perturbed parameters. While ensemble data sets are a powerful tool for mitigating uncertainty, they pose significant visualization and analysis challenges due to their complexity. We present "Ensemble-Vis", a framework consisting of a collection of overview and statistical displays linked through a high level of interactivity for gaining key scientific insight into the distribution of the simulation results as well as the uncertainty associated with the data. In contrast to methods that present large amounts of diverse information in a single display, we argue that combining multiple linked statistical displays yields a clearer presentation of the data and facilitates a greater level of visual data analysis. We demonstrate this approach using driving problems from climate modeling and meteorology and discuss generalizations to other fields.

- *Speaker:* Kristi Potter (SCI), http://www.sci.utah.edu/~kpotter/

- *Where:* Conference Room 3760

- *When:* Friday noon (11/13)

## November 6, 2009

- **Depth Dependent Halos** (VIS paper discussion)

- *Speaker:* Mark Kim (SCI), http://www.cs.utah.edu/~mbk/

- *Where:* Conference Room 3760

- *When:* Friday noon (11/06)

## November 6, 2009

- **A User Study to Compare Four Uncertainty Visualization Methods for 1D and 2D Datasets** (VIS paper discussion)

- *Speaker:* Blake Nelson (SCI), https://www.sci.utah.edu/people/bnelson.html

- *Where:* Conference Room 3760

- *When:* Friday noon (11/06)

## November 6, 2009

- **Structuring Feature Space: A Non-Parametric Method for Volumetric Transfer Function Generation** (VIS paper discussion)

- *Speaker:* Evrard Ohou (SCI), http://www.sci.utah.edu/people/eohou.html

- *Where:* Conference Room 3760

- *When:* Friday noon (11/06)

## October 30, 2009

- **Exploring the Millennium Run - Scalable Rendering of Large-Scale Cosmological Datasets** (VIS paper discussion)

- *Speaker:* Linh Ha (SCI), http://www.cs.utah.edu/~lha/

- *Where:* Conference Room 3760

- *When:* Friday noon (10/30)

## October 30, 2009

- **Volume Ray Casting with Peak Finding and Differential Sampling** (VIS paper discussion)

- *Speaker:* Carson Brownlee (SCI), http://www.cs.utah.edu/~brownlee/grapes/Welcome.html

- *Where:* Conference Room 3760

- *When:* Friday noon (10/30)

## October 9, 2009

- **An Interactive Visualization Tool for Multi-channel Confocal Microscopy Data in Neurobiology Research (VIS practice talk)**

Confocal microscopy is widely used in neurobiology for studying the

three-dimensional structure of the nervous system.

Confocal image data are often multi-channel, with each channel resulting

from a different fluorescent dye or fluorescent protein; one channel may

have dense data, while another has sparse; and there are often structures at

several spatial scales: subneuronal domains, neurons, and large groups of

neurons (brain regions). Even qualitative analysis can therefore require

visualization using techniques and parameters fine-tuned to a particular

dataset. Despite the plethora of volume rendering techniques that have been

available for many years, the techniques standardly used in neurobiological

research are somewhat rudimentary, such as looking at image slices or

maximal intensity projections. Thus there is a real demand from

neurobiologists, and biologists in general, for a flexible visualization

tool that allows interactive visualization of multi-channel confocal data,

with rapid fine-tuning of parameters to reveal the three-dimensional

relationships of structures of interest. Together with neurobiologists, we

have designed such a tool, choosing visualization methods to suit the

characteristics of confocal data and a typical biologist's workflow. We use

interactive volume rendering with intuitive settings for multidimensional

transfer functions, multiple render modes and multi-views for multi-channel

volume data, and embedding of polygon data into volume data for rendering

and editing. As an example, we apply this tool to visualize confocal

microscopy datasets of the developing zebrafish visual system.

- *Speaker:* Yong Wan (SCI), http://www.sci.utah.edu/people/wanyong.html

- *Where:* Conference Room 3760

- *When:* Friday noon (10/09)

## October 9, 2009

- **Loop Surgery for Volumetric Meshes: Reeb Graphs Reduced To Contour Trees (VIS practice talk)**

This paper introduces an efficient algorithm for computing the Reeb graph of a scalar function f defined on a volumetric

mesh M in R^3. We introduce a procedure called loop surgery that transforms M into a mesh M' by a sequence of cuts and guarantees

the Reeb graph of f (M') to be loop free. Therefore, loop surgery reduces Reeb graph computation to the simpler problem of

computing a contour tree, for which well-known algorithms exist that are theoretically efficient (O(n log n)) and fast in practice.

Inverse cuts reconstruct the loops removed at the beginning.

The time complexity of our algorithm is that of a contour tree computation plus a loop surgery overhead, which depends on the

number of handles of the mesh. Our systematic experiments conﬁrm that for real-life volumetric data, this overhead is comparable

to the computation of the contour tree, demonstrating virtually linear scalability on meshes ranging from 70 thousand to 3.5 million

tetrahedra. Performance numbers show that our algorithm, although restricted to volumetric data, has an average speedup factor of

6,500 over the previous fastest techniques, handling larger and more complex data-sets.

We demonstrate the versatility of our approach by extending fast topologically clean isosurface extraction to non-simply connected

domains. We apply this technique in the context of pressure analysis for mechanical design. In this case, our technique produces

results in matter of seconds even for the largest models. For the same models, previous Reeb graph techniques do not produce a

result.

- *Speaker:* Julien Tierny (SCI), http://www.sci.utah.edu/~jtierny

- *Where:* Conference Room 3760

- *When:* Friday noon (10/09)

## October 2, 2009

- **VisMashup: Streamlining the Creation of Custom Visualization Applications (VIS practice talk)**

- *Authors:* Emanuele Santos, Lauro Lins, James P. Ahrens, Juliana Freire, and Claudio T. Silva

Visualization is essential for understanding the increasing

volumes of digital data. However, the process required to create

insightful visualizations is involved and time consuming. Although

several visualization tools are available, including tools with

sophisticated visual interfaces, they are out of reach for users who

have little or no knowledge of visualization techniques and/or who

do not have programming expertise. In this paper, we propose

VisMashup, a new framework for streamlining the creation of

customized visualization applications. Because these applications

can be customized for very specific tasks, they can hide much of the

complexity in a visualization specification and make it easier for

users to explore visualizations by manipulating a small set of

parameters. We describe the framework and how it supports the

various tasks a designer needs to carry out to develop an

application, from mining and exploring a set of visualization

specifications (pipelines), to the creation of simplified views of

the pipelines, and the automatic generation of the application and

its interface. We also describe the implementation of the system

and demonstrate its use in two real application scenarios.

- *Speaker:* Emanuele Santos (SCI), http://www.sci.utah.edu/~emanuele/

- *Where:* Conference Room 3760

- *When:* Friday noon (10/02)

## September 18, 2009

- **First steps towards quantifying confidence (Summer internship)**

Whenever a decision is made, circuitry of the brain is engaged based on

the difficulty of the task at hand. By carefully monitoring the neural

circuit responsible for error detection and handling, we have shown the

ability to determine whether the response given is correct or

incorrect. However, preliminary results indicate that based on the

spectral dynamics generated by the brain circuit involved, an objective

measure of a person's confidence in their answer can be derived.

- *Speaker:* Erik Anderson (SCI), http://www.sci.utah.edu/~eranders/

- *Where:* Conference Room 3760

- *When:* Friday noon (09/18)

## September 18, 2009

- **Stratified representation scheme for subsurface modeling (Summer internship)**

The steps involved in oil reservoir modeling are similar to the traditional scientific pipeline:

a model has to be updated each time new data comes in; afterwards, the new model is used for simulations

which in turn help scientists with the decision-making process. Current tools cannot easily handle

model updates due to limitations of the underlying framework – often the model must be rebuilt from scratch.

In this talk we will present a flexible framework for domain decomposition and surface manipulation.

During last summer, we have built a prototype of a modeling tool based on this flexible framework

providing a few key functionalities for geologists and geophysicist to perform surfaces updates.

- *Speaker:* Tiago Etienne Queiroz (SCI), http://www.sci.utah.edu/~etiene/

- *Where:* Conference Room 3760

- *When:* Friday noon (09/18)

## September 11, 2009

- **Topological Analysis of 2D Steady Vector Fields**

Vector fields arise widely in various

engineering applications. Topological analysis extracts

the qualitative information (i.e. structure) of a provided

vector field. The topology of a vector field consists of a

set of features of interest and their connectivity which

forms a graph called topological graph. This graph

segments the data domain into a number of sub-regions in

each of which the flow behavior possesses the same nature.

Therefore, topological analysis provides an efficient

means for the engineers to investigate the behaviors of

their data. In this talk, I will focus on the topology of

2D steady vector fields which is well defined. I will

briefly explain why engineers are interested in certain

features in 2D steday vector fields. Also, I will review

some techniques of extracting these features and

constructing the topological graphs with the focus on my

PhD work including ECG and MCG computation. To learn more

about what they are, please come to the talk.

- *Speaker:* Guoning Chen (SCI), http://oregonstate.edu/~cheng/

- *Where:* Conference Room 3760

- *When:* Friday noon (09/11)

## September 4, 2009

- **Delaunay Methods for Approximating Geometric Domains**

The Delaunay triangulation is used extensively for representing geometric

domains. In this talk, I consider the use of the Delaunay triangulation for

approximating two different domains. First, I present an algorithm, DelIso,

for building Delaunay meshes to approximate smooth surfaces defined by the

isosurfaces of volume datasets. DelIso employs a two stage algorithm which

discards the need to maintain the full 3D Delaunay triangulation in the second

stage. Implementation results have shown that by using this optimization we

can obtain a 2-3 times speedup over its one stage counterpart.

The second domain investigated is piecewise smooth complexes (PSCs). One of

the limitations of past meshing algorithms is that they could only be applied

to either smooth surfaces or polyhedral domains. PSCs are a more general

class where the shape is modeled as a collection of smooth patches that can

meet sharp corners as well as non-manifolds. We have designed DelPSC, an

algorithm to build Delaunay meshes that approximate PSCs. DelPSC was designed

to be easily implementable, removing the need for many of the expensive

computations that previously made Delaunay meshing for PSCs impractical. Its

meshing strategy employs a novel protection scheme to preserve sharp features

throughout the refinement. We can also guarantee that by reducing a single

scale parameter, the correct topology is achieved for the output mesh. The

approach used in DelPSC allows for meshing a wide variety of objects such as

non-smooth CAD parts and non-manifold objects.

- *Speaker:* Joshua A. Levine (Ohio State University), http://www.cse.ohio-state.edu/~levinej/

- *Where:* Conference Room 3760

- *When:* Friday noon (09/04)

## August 28, 2009

- **Topology-based systems for data analysis and visualization**

Topological techniques have become popular for the analysis of scalar

functions, for example, for automatic feature detection and

extraction. In this informal talk, I will present an overview of the

various software solutions we are developing to solve data analysis

and visualization problems. Some topological methods currently in

development at SCI utilize Reeb graphs, Morse-Smale complexes and

Jacobi sets. Some motivation and basic background for these techniques

will be presented in the talk. In particular, the main focus of the

talk will be covering the breadth of techniques that are currently

being developed here, and an overview of the state of the software

implementations.

- *Speaker:* Attila Gyulassy (SCI), http://idav.ucdavis.edu/~jediati/

- *Where:* Conference Room 3760

- *When:* Friday noon (08/28)

## Open Discussion and Semester Planning

A common practice for VisLunch is to use some of its

sessions as a mean to let people know about the work

of the new people around: new faculties, new post docs,

new PhD. students . As there are lots of new faces

around, we hope to schedule some of these presentations

in this session.

- **Summer Internships**

Hurrah! It's back to school time!

PhD. Students are strongly invited to schedule a VisLunch talk (~ 30 minutes)

to present the work they accomplished during their summer internship.

- **IEEE VIS talks**

Wow! SCI rocked once again at IEEE VIS this year!

If you're the presenter of an accepted VIS paper, please let

us know and we'll schedule a session for you so you can practice your talk.

This semester Julien Tierny and Attila Gyulassy will be responsible

for organizing the VisLunch sessions. Please feel free to contact them

for any question regarding VisLunch or for scheduling a talk:

Julien Tierny Attila Gyulassy Room: 4660 Phone: 585-3911 jtierny at sci dot utah dot edu, aggyulassy at ucdavis dot edu

Information regarding the VisLunch sessions will posted on this wiki page (http://www.vistrails.org/index.php/VisLunch/Fall2009)