VisIt 2.0 Features Brad Whitlock

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

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

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)

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

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

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

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

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

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)

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)

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

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

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

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

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.

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

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-users@email.ornl.gov) VisIt developer’s list (visit-developers@email.ornl.gov) VisIt forum (http://www.visitusers.org/forum/forum.pl)