Editing IBM OpenDX

{{Infobox software
| name                   = IBM OpenDX
| logo                   = Opendx-logo.jpg
| screenshot             = Opendx-screenshot2.jpg
| caption                = Visualization of a scalar field
| developer              = 
| released               = 
| latest preview version = Through [[Concurrent Versions System|CVS]]
| programming language   = Mainly [[C (programming language)|C]]
| operating system       = [[Cross-platform]]
| language               = 
| genre                  = [[List of graphing software|Plotting]]
| license                = [[IBM Public License]]
| website                = {{URL|www.opendx.org}}
}}
'''OpenDX''' stands for '''Open Data Explorer''' and is [[IBM]]'s [[Scientific visualization|scientific data visualization]] [[software]]. <!-- OpenDX is a [[visualization (graphic)|visualization]] program for complex [[data]]. Complex meaning more than one [[dimension]]. --> It can handle complex domains (such as a mechanical [[gear]] or a human [[brain]]) along with [[measurement|measured]] or [[computer simulation|computed]] data. The data may be [[Scalar field|scalar]] (such as the concentration of a chemical agent in the brain), [[vector field|vector]] or [[tensor field|tensor]] fields (like the displacement or [[strain tensor]] fields when the gear is in action) at different points of the object. The points at which data is measured don't have to be equally spaced and not need to be homogeneously spaced. The project started in 1991 as ''Visualization Data Explorer''.
<!--
Many [[Computer program|programs]] make nice [[information graphic|graphs]] of a [[function (mathematics)|function]] like <math>y=f(x)</math>, or represent discrete points data <math>(x_i,y_i)</math> as a curve. [[OpenDx]] is oriented to more complex data is more complex data as a set of surface heights as a function of positions <math>z=f(x,y)</math> or arrays like <math>(x_i,y_i,z_i)</math>. -->

''OpenDX'' can produce 3D images with the quantities plotted as color or gray-scale coded, or as [[vector graphics|vectors]], [[Streamlines, streaklines, and pathlines|streamlines]] and ribbons. It allows the object to be sliced to obtain a view of the internal structure, and then represent the data on this slice plane as a height-coded graph. It can rotate the object to provide a view of the data from any angle and allows [[Computer animation|animations]] of this motion to be made.

== Graphical user interface ==

''OpenDX'' is based on the [[Motif (software)|Motif]] widget toolkit on top of the [[X Window System]]. Its [[graphical user interface]] has a wide variety of [[InterActor|interactors]], both direct and indirect. Direct interactors allow the user to directly manipulate images (e.g. [[rotate]] or [[Page zooming|zoom]]). Indirect interactors ([[Rotary dial|dials]], [[Switch statement|switches]], [[Button (computing)|buttons]], sliders) enable the user to control various aspects of her visualization. Interactors are ''smarter'' because they are data-driven. Interactors are auto-ranging and self-limiting. They examine the data and, depending on its type, will determine the [[minimum]] and [[maximum]] of the data, or create a list for an option [[menu (computing)|menu]] based on the data. The user can even set the label of the interactor based on some aspect of the data (e.g., [[Metadata (computing)|metadata]]).

[[File:opendx-screenshot.jpg|frame|none|OpenDX screen shot showing the Visual Program Editor and several interactors]]

The data-driven concept is not simply for sliders, dials and option menus. It also applies to vector interactors. These reconfigure themselves based on the dimensionality of the data. They also auto-range themselves based on the maximum and minimum of each vector component.

== Design ==

Data Explorer is a system of tools and user interfaces for visualizing data. In general terms the visualization of data can be considered a 3-stage process:

* Describing and importing data
* Processing the data through a visualization program
* Presenting the resulting image.

The principal components of '''OpenDX''' are

; Data model: This is the set of definitions, rules, and conventions used to describe Data Explorer entities (including data fields, geometrical objects, and images).

; Data Prompter: A user interface for describing data to be imported into Data Explorer.

; Data Browser: A user interface for viewing a data file, determining the layout and organization of the data it contains, and transferring this information to the Data Prompter.

; Scripting Language: A high-level language for creating visualization programs. It can also be used directly in a command mode to perform various tasks. Visual programs—i.e., the visualization programs displayed in the Visual Program Editor window as ''networks'' of module icons—are also written in the scripting language. A visual program constructed in this window by the user is translated into the same language when it is saved to disk.

; Visual Program Editor (VPE): A graphical user interface for creating and modifying visual programs (networks). Programs created with this editor are translated into the scripting language by Data Explorer and are stored in that form.

; Modules: The ''building blocks'' (visualization ''tools'') that constitute a visual program network. They can be directly accessed and manipulated in the ''Visual Program Editor''.

; Module Builder: A user interface for creating customized modules to be used in visual programs.

; Image Window: An interactive window for viewing and modifying the presentation of the image produced by a visual program.

; Control Panels: A user interface for changing the parameter values used by a visual program.

== Screen shots ==

=== Visualization of a scalar field ===

[[File:opendx-screenshot2.jpg|frame|none|OpenDX screen-shot showing visualization of a scalar field.]]

In this example we show the visualization of the flow of a particulated material (dust) inside a building. In this case the quantity visualized is a scalar, namely the concentration of the particles. The concentration of particles at each point in space is represented using colors. The reader can deduce the concentration by comparing the colors with the ''colorbar'' at the right upper corner of the image. To improve the visualization the drawing is shadowed as if it had an elevation in the direction normal to the plane proportional to the concentration. In '''OpenDX''' this is called the ''rubber-sheet'' effect.

=== Visualization of vector fields ===

{|
| [[File:opendx-cubcav1.jpg|300px]] 
| [[File:opendx-cubcav2.jpg|300px]] 
|- 
| [[File:opendx-cubcav3.jpg|300px]] 
| [[File:opendx-cubcav4.jpg|300px]] 
|}

[[Vector fields]] are harder to visualize than scalar ones. Consider in this case
the flow in a cubic cavity (the 3D version of the well studied
[http://www.mathematik.uni-dortmund.de/~featflow/album/dc.html square cavity] benchmark. The use of [[Streamlines, streaklines, and pathlines|streamlines]] helps in realizing the direction of the flow. The ''rockets'' (the big red arrows on the top of the cavity) represent the imposed flow.

<!--
To be short, OpenDX is one of the best visualisation programs out there, and it is free ! Twenty years ago, when IBM made the program, there were big computer centers on campuses and research centers who could afford to buy the product for a lot of money. Then PCs became available and powerful, capable of running such a heavy program; IBM on the other judged probably that the cost of maintenance of the program was higher than the revenue from it, and decided to opensource it. 
The program was made by engineers for engineers, so it will seem a little heavy at the beginning. If however, you have complex data on a regular basis, it is definitively a good choice.
-->

==External links==
*{{official website|www.opendx.org}} (out-of-date)
*[http://www.vizsolutions.com/ Commercial support, physical media] (out-of-date)
*[http://www-beams.colorado.edu/dxhdf5/ module] for reading [[HDF5]] files

[[Category:Data and information visualization software]]
[[Category:Free software programmed in C]]
[[Category:IBM software|OpenDX]]