1. VisIt 2.0 Features
Brad Whitlock

2. Overview VisIt Background Better Practices GUI Facelift
File Reader Improvements
Volume Plot
Streamline Plot
Data Analysis
Data Binning
Python Filters
Selections
Alternate user interfaces
In-situ visualization

3. VisIt Background Started at LLNL in 2000 R&D 100 award winner in 2005
VisIt is an open source data analysis and visualization application designed to process extremely large data sets. VisIt is often used for interactive data exploration, comparative analysis, visual debugging, quantitative analysis, and presentation graphics.
Started at LLNL in 2000
R&D 100 award winner in 2005
VisIt has spread to many other labs and universities
VisIt is actively developed at
LLNL
Oak Ridge National Lab
Lawrence Berkeley Lab
UC Davis
University of Utah
TACC
Used by end-users
Used to deploy research

4. VisIt can handle your data
VisIt can handle the largest datasets
VisIt has run at scale on 64K processors on LLNL’s dawn (June 2009)
VisIt was able to handle an 8 trillion cell dataset using 12K processors on LLNL’s graph cluster
Core-collapse supernova simulation from the CHIMERA code
(image by Hank Childs)

5. Rich Data Model Read over 100 file formats
AMR
Unstructured
Rectilinear
Curve
Points
Curvilinear
Molecular data
CSG
Read over 100 file formats
Plugin architecture makes it easy read new formats or add new plots and operators
Rich data model
Meshes
Points
Curves
Structured
Unstructured
AMR
CSG
Fields
Materials
Species
Molecular data

6. VisIt architecture 4 main components
Graphical User Interface (GUI)
Viewer
Database server
Compute engine
GUI and Viewer usually meant to run locally on your desktop computer
Database server and parallel compute engine can run on remote computers where the data files are located and talk to the GUI and viewer running on your desktop computer
Desktop computer
GUI Viewer
Database server
Parallel compute engine
Parallel compute engine
Parallel compute engine
Parallel compute engine
Data files
Remote computer

7. Better Practices Redmine Online bug tracker at visitbugs.ornl.gov
New CMake build system
1 source of build logic for all platforms
Build system automatically generated
No separate Windows build system anymore!
Continuous integration builds on different platforms using buildbot
Nightly regression testing
Redmine

8. GUI Facelift Ported VisIt to Qt 4
1.12
2.0
Ported VisIt to Qt 4
Selected files list gives way to Open files
Plot and Operator windows group related options
Operators are now categorized
Customizable
Allows all operators to be enabled
Redesigned host profiles window is easier to setup and manage profiles
Internationalization support
A user contributed a Dutch translation

9. File Reader Improvements
Automatic file format detection was greatly improved
Many improved readers
Silo reader uses Silo 4.7
Some readers can prompt VisIt to ask the user to fill in options that help the reader read the data correctly
New readers
Velodyne
MatrixMarket
Xdmf
AdventureIO
PFLOTRAN
STAR
GULP
PuReMD
XML schema describes how to read HDF5 files

10. Volume Plot
The Volume plot lets you use color and opacity to examine the interior structure of 3D scalar fields.
Ray-caster has been overhauled
Fewer samples are required to make good pictures
Lighting has been improved
Added support for 2D transfer functions
The GUI shows histograms of the data to guide transfer function creation
(image from FLASH center)

11. 10K streamlines through a flow jet (image by Hank Childs)
Streamline Plot
The Streamline plot lets you examine vector flow fields by advecting massless particles from seed locations to see where they flow.
Totally rewritten for 2.0
Streamlines can integrate across domain boundaries
Streamlines are AMR-aware and use the data for the appropriate AMR level
Performance enhanced with threads and adaptive communication strategies
Many new seeding options
10K streamlines through a flow jet (image by Hank Childs)

12. Data Analysis Data-Level Comparison Wizard
Simplifies comparison of data on different meshes by setting up CMFE expressions
Data can be in the same database
Data can be in different time steps
Data can be in different databases
VisIt has new types of expressions for time iteration
Calculate the maximum, minimum or average value at a location
Calculate the time when a condition occurs (e.g. time when the maximum value at a location occurs)
Check Expressions Window for Time Iteration

13. Data Binning
DataBinning operator lets you relate multiple variables and bin them up to compute various quantities per bin
Sum
Count
Probability Density Function
Statistics
Average
Variance
Standard deviation
Min
Max
RMS
Add the DataBinning operator directly from plot menus

14. Python Filters
Parallel engine
Data source
Expression filter
Filter
Python
User-defined Python expression
VisIt now supports writing custom expressions and queries in Python
Enter Python expressions into the Expression window’s Python tab
Python interpreter embedded in the compute engine
Data gets passed as Python-wrapped VTK objects to user-defined Python code
Use VTK Python functions to manipulate data and perform calculations

15. Selections
A selection is a reduced set of cells isolated from a dataset using VisIt's various methods of dataset reduction (threshold, slicing, clipping, etc.)
Selections can be applied to other plots, making it easy to look at different views of the data
Selections are linked to plots
The Selection window creates a selection from the active plot
Selections are applied to plots via the Subset window
A selection defined by the ParallelCoordinates plot isolates cells in the original mesh

16. Alternate User Interfaces
Java interface
Python interface
GUI
C++ interface
Host application
VisIt provides C++, Python, Java bindings to its ViewerProxy object
Use to create client applications that control VisIt’s viewer
GrizIt: a Python GUI that makes VisIt look like Griz
VisIt’s viewer can be directly embedded in Qt applications, giving them all of VisIt’s abilities
Vorpal Composer: an embedded VisIt application from Tech-X corp.

17. In-situ visualization
VisIt provides libsim, which is a library that can let VisIt connect to your simulation code and operate in-situ on its data arrays.
Run the simulation and connect with VisIt
You will be able to perform any of VisIt’s operations on your simulation data
Advance the simulation and watch your plots update
Add functions to your simulation that let VisIt connect
Add functions to your simulation that expose your arrays as data VisIt will process
Link your simulation with libsim
New libsim features
Species
Vector,Tensor data
AMR meshes
CSG meshes
Users don’t allocate memory
Additional error checking
Single style for C and Fortran
Simulation
libsim
Glue code
VisIt runtime
data
commands

18. Resources For more information about VisIt’s newer features, see
Release notes
Visitusers.org
Contacting the VisIt team
VisIt help line (42-VIS)
VisIt user’s list
VisIt developer’s list
VisIt forum (