File last modified 11 December 2000
24.3 Other Software Packages
There are a large number of scientific visualization software packages in circulation today. Here we are going to mention only two that we have found particularly useful. The first one is The Generic Mapping Tool (GMT) that produces very high quality PostScript figures that are excellent for publication purposes. The second one is actually a class of tools, we mention two of them AVS and NAG Explorer, both of which are data visualization and manipulation tools.
Two graduate students (Paul Wessel and Walter H. F. Smith) produced the first version of GMT while they were at the Lamont-Doherty Earth Observatory. Since then they have worked hard at improving and modifying the code to produce better and better graphics even though their careers have taken them far from New York (Wessel: U. of Hawaii, Smith: NOAA NOS). GMT is a free, public-domain software package maintained by Wessel and Smith.
The Generic Mapping Tool is a series of shell scripts (in UNIX) that produce a PostScript file as its final output. Unless you specify otherwise, each subsequent shell script just adds more PostScript code to the original output file. This has the effect of overlaying the most recent mapping commands onto the previous mapping commands. The output PostScript file is of "camera ready" quality.
Figure 24.3.1 shows how data processed in MATLAB and then written out in either ASCII, netCDF or binary format can be combined to produce very high quality graphics. Many times the output of GMT will be a map, however, other types of plots are also possible (line drawings, surface plots, etc.). The last digit of the colorbar in Fig. 24.3.1 was cropped during the conversion of the PostScript file to this GIF image and does not reflect on the quality of the GMT output.
AVS and NAG Explorer are two software programs produced by two different companies, but what they do and how they operate is very similar. Bill likes AVS, but I like Explorer. Whatever I say about Explorer is generally true about AVS, although the details might be a bit different.
Explorer is a system for combining small, general tools called modules to create powerful custom visualization applications. Modules linked together this way form an Explorer Map (see Fig. 24.3.2). The Map Editor is the primary means of interacting with modules that are cooperating as an aggregate Explorer application. The Map Editor is used to start and stop module execution, make and break connections among modules (the lines seen in Fig. 24.3.2), and operate controls for the modules themselves.
There is a "library" of these modules and some already completed "maps". You can build your own applications by dragging the desired modules onto the map editor window and hook them up to control the flow of information, don't worry the map editor won't let you hook them up in an illegal fashion. It is best, when first beginning, to try to take some of the supplied maps and modify them to your needs. In this fashion you will get a better appreciation for how the system of modules interact with each other, then you can branch out and build your own maps. When you are done, you can save your maps in a library of your own for future use.
Building the "maps" is just the beginning of what you can do with these software tools. Figure 24.3.3 shows you one type of "final product" Explorer produces, the "render" window. The "map" in Fig. 24.3.2 displays some 3-D data in the render tool window and the controls around the edge allow you to rotate, slice and dice, magnify, and perform other manipulations on the rendering. You can even "fly" through your data!
All of these packages have extensive User Guide information and some also have tutorials to help you get started. The guides are often stored as PDF or PostScript files on the system where the software resides. If not, much (all?) of it is also available on the web.
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