Visualisation with Open Data Explorer
This is a (rather sparse) collection of resources for DX (Data
Explorer), an open source program for interactive visualisation of
You can find much more information on other web sites, see the
corresponding section below.
Data Explorer can be obtained from the
OpenDX Download page.
The OpenDX documentation
is a bit voluminous for my taste.
It is available in PostScript and HTML; a lot of information is also
available through the `Help' menu in the main DX window (on Debian
systems, you will need to install the package `dx-doc' in addition to `dx'
for the online help to be available).
The documentation explicitly refers to a number of sample programs, which
you can find (nicely packed together) on IBM's
Page as `OpenDxSamples'.
If you need the really latest version of a sample file (I doubt they are
changing a lot, though), you can check it out from the
You will definitively need these sample files if you want to profit from
One problem is that there are far too many sample programs for beginners
and it is difficult to get an overview over which ones are very
fundamental and which are more advanced.
For this reason, I have created a few, relatively simple, sample
programs which nevertheless progress from very simple to really useful.
You find them in the examples/
The data are velocity, density and magnetic field for a simulation of
magnetic field generation by the screw dynamo in spiral Couette flow.
All data are given on a three-dimensional grid.
The spatial resolution is 24x24x30 points and was chosen rather low for
the sake of finite download times.
To run the examples, you need to
Each example contains an annotation outlining the program structure and
- get the examples if you have not already done so:
- download the tarball
- unpack it with
tar xvf dx-intro.tar
- change to the directory dx-intro/examples
- start dx with the first example
dx -edit simple1
- click Execute --> Execute Once to run it
So far, there is only one, but I think it is quite useful.
dx_export.pro is an IDL subroutine that
writes three-dimensional data in DX-readable form and at the same time
generates a header file telling DX everything it needs to know
about the data structure and layout.
See `How to produce the header
file' for an example of how to use it --- or just have a look at the
documentation in the header of the file itself.
...in approximate order of (arguable) importance.
- The first example is discussed
on a separate page.
It plots a density isocontour.
- Does the same thing as simple1.net, but in a slightly
- Still draws a density isocontour, but adds a bounding box and
allows the user to specify the contour level.
- Plots two partially transparent isosurfaces of magnetic field
- Like med1.net, but with additional arrows representing
- This one is supposed to show off, while still being understandable
Different tasks are split into different `pages' to keep the
program from becoming 2-dimensional Spaghetti code.
- Import -- import data from a file
- Select -- select members of a group (e. g. individual variables or
- Image -- render and display an image
- ShowBox -- produce lines representing the bounding box
- Isosurface -- produce isosurface
- Collect -- collect objects into a group (in particular to merge
- Compute -- perform point-wise arithmetic to one or several fields
- AutoGlyph -- produc glyphs (e. g. arrows for vector fields)
- Tube -- produce tube of finite diameter around lines (like
fieldlines or the bounding box)
- Describe -- tell what data these are
My Second Top Ten Modules
- Switch -- a kind of if or select statement
- Interactors -- in particular Scalar and Selector
- Include -- excludes points based on data value
- Reduce -- reduce resolution
- Slab -- extract a Cartesian slab of data
- Streamline -- compute field lines
- Ribbon -- produce a ribbon around a line (with writhe for the curl
of the vector field)
- Color, AutoColor -- color the input object
- Transmitter, Receiver -- wireless transfer of data between different
pages (the only way to avoid 2-d spaghetti code)
- Statistics compute mean, standard deviation/variance, minimum and
maximum of a field
General information and tutorials
Add-ons and extensions
This is not supposed to be a real troubleshooting page.
I am just documenting one problem I encountered running DX on Debian:
Whenever I tried to write and apply an annotation, DX crashed.
Apparently, this was due to problems with the lesstif library
(lesstif1_0.89) --- after upgrading to lesstif1_0.92, the problem was
by Wolfgang Dobler
Any comments are appreciated. Please send them to