2.1. Supported File Types

VisIt can create visualizations from databases that are stored in many types of underlying file formats. VisIt has a database reader for each supported file format and the database reader is a plugin that reads the data from the input file and imports it into VisIt. If your data format is not listed in File formats supported by VisIt then you can first translate your data into a format that VisIt can read (e.g. Silo, VTK, etc.) or you can create a new database reader plugin for VisIt. For more information on developing a database reader plugin, refer to the Getting Data Into VisIt manual or contact us via Getting help.

2.1.1. File extensions

VisIt uses file extensions to decide which database reader plugin should be used to open a particular file format. Each database reader plugin has a set of file extensions that are used to match a filename to it. When a file’s extension matches (case sensitive except on MS Windows) that of a certain plugin, VisIt attempts to load the file with that plugin. If the plugin cannot load the file then VisIt attempts to open the file with the next suitable plugin, before trying to open the file with the default database reader plugin. If your files do not have file extensions then VisIt will attempt to use the default database reader plugin. You can provide the -default_format command line option with the name of the database reader plugin to use if you want to specify which reader VisIt should use when first trying to open a file. For example, if you want to load a PDB/Flash file, which usually has no file extension, you could provide: -default_format PDB on the command line.

2.1.2. Example Data Files

As part of VisIt’s regular testing, a number of example data files VisIt reads can be found in VisIt’s data subdirectory of the main code repository. In particular, if you are looking for examples of various of the human readable ASCII formats VisIt reads so that you can produce a compatible file, you may find examples there that help.

2.1.3. More Details of ASCII Formats

Here we describe more details specific to some of the ASCII formats VisIt reads.

2.1.3.1. Creating .visit Files

To create a .visit file, simply make a new text file that contains the names of the files that you want to visualize and save the file with a .visit extension.

  • Visit will take the first entry in the .visit file and attempt to determine the appropriate plugin to read the file.
  • Not all plugins can be used with .visit files. In general, MD or MT formats sometimes do not work.
    • An MT file is a file format that provides multiple time steps in a single file. Thus, grouping multiple MT files to produce a time series may not be supported.
    • An MD file is one that provides multiple domains in a single file. Thus, grouping multiple MD files to produce a view of the whole may not be supported.

Here is an example .visit file that groups time steps together. These files should contain 1 time step per file.

timestep0.silo
timestep1.silo
timestep2.silo
timestep3.silo
...

Here is an example .visit file that groups various smaller domain files into a whole dataset that VisIt can visualize. Note the use of the !NBLOCKS directive and how it designates the number of files in a time step that constitute the whole domain. The !NBLOCKS directive must be on the first line of the file. In this example, we have 2 time steps each composed of 4 domain files.

!NBLOCKS 4
timestep0_domain0.silo
timestep0_domain1.silo
timestep0_domain2.silo
timestep0_domain3.silo
timestep1_domain0.silo
timestep1_domain1.silo
timestep1_domain2.silo
timestep1_domain3.silo
...

You may also explicitly indicate the time associated with a file (or group of block files) using the !TIME directive like so…

!NBLOCKS 4
!TIME 1.01
timestep0_domain0.silo
timestep0_domain1.silo
timestep0_domain2.silo
timestep0_domain3.silo
!TIME 2.02
timestep1_domain0.silo
timestep1_domain1.silo
timestep1_domain2.silo
timestep1_domain3.silo
...

2.1.3.2. Point3D Files

Point3D files are four or fewer columns of ASCII values with some header text to indicate the variable names associated with each column and a coordflag entry to indicate how to interpret the columns of data as coordinates. Point3D files can be used to define discrete points in 1, 2 and 3 dimensions having a single scalar value associated with each point. Some examples are below. The Point3D file…

x y z value
0 0 0 0
0 0 1 1
0 1 0 2
0 1 1 3
1 0 0 4
1 0 1 5
1 1 0 6
1 1 1 7

Defines a collection of 8 points in 3 dimensions have a scalar variable named value. Below, the #coordflag directive is used to define the same collection of 8 points in 3 dimensions as the previous example except where the columns holding the z-coordinate and the scalar variable are interleaved.

 x y value z
 #coordflag xyvz
 0 0 0 0
 0 0 1 1
 0 1 2 0
 0 1 3 1
 1 0 4 0
 1 0 5 1
 1 1 6 0
 1 1 7 1

In the example below, the #coordflag directive is used to define a collection of points in two dimensions where each point has a velocity magnitude value associated with it.

x y velocity
#coordflag xyv
0 0 1
0 1 1.01
1 0 2.02

Likewise, for a collection of points in just one dimension, we would have

x y velocity
#coordflag xv
0 1
1 1.01
2 2.02

There are some additional examples of Point3D files on the VisIt wiki pages.