This month's column completes our alphabetic journey through Computer Aided Design (CAD) and simulation systems. I hope you've enjoyed the ride so far; I'm happy to report that it closes with a real bang!


XSAT is an X-based satellite tracker which draws maps of various world regions and plots satellite ground tracks, complete with timestamps. XSAT also produces a list of visible orbit passes for a given city, with extensive information on azimuth and time. It can also produce a PostScript file which gives a hard copy of all displayed information. XSAT is available in

C++Sim and Maisie

C++Sim and Maisie are simulation tools, but they are also parallel programming systems. Consequently, they have been covered in previous columns. For information on C++Sim, see the October 1994 Internet Notebook column (Parallel Programming Languages, Part I, p. 85) or FTP to Maisie (*) is covered in the following month's column (Parallel Programming Languages, Part II, p. 109).


I covered Netlib a bit, back in May 1994 (More Math Madness, p. 93). For our purposes this month, however, it's enough to say that Netlib is a world-famous collection of mathematics and simulation tools.

Don't try to download the whole thing, it's huge! Instead, browse around until you find some interesting stuff. Netlib is available at


BRL-CAD is a humongous collection of CAD software, developed by the U.S. Army's Ballistic Research Laboratory. Here is a brief description, taken from their overview document:

Given the origin of the package, it should not be surprising that some of the system's features have a distinctly military focus. The models can be analyzed for various physical properties (such as center of mass and moments of inertia), but also for vulnerability and for optical, radar, and IR signatures. Somewhat unusual materials (e.g., depleted uranium) can be used in the model, to make things realistic.

People, this system is huge: hundreds of thousands of lines of C code. Using a wealth of batch-mode and interactive utilities, the user builds up a geometric model of a scene. The user then "interrogates" the model to get graphic renderings and other useful information. For instance, by using ray tracing and radiosity techniques, the user can get high-quality images of the scene.

I hope I have convinced you that this is not a trivial piece of software, but that it could be a gold mine for the right person or company. Now for the tricky part: BRL-CAD isn't unrestricted software. In order to get BRL-CAD, you have to fill out and send in a registration form. Once the form has been processed, you will be sent both a decryption key and a substantial stack of manuals.

You can then download the compressed archives (the current release is about 18 megabytes) decrypt and uncompress them, and feed them to tar. This should yield a little less than 50 megabytes of source code. I have no idea how much room you'll need for binaries, but a few hundred megabytes should get you well started (:-).

I find myself confused, however, by the distribution restrictions. If I were told that BRL was trying to keep dangerous technology out of Qaddafi's hands, I could understand: why tell him how to design tanks? That doesn't seem to be the primary goal, however. Nor does it appear that some corporate developer is trying to hold on to the material for proprietary gain.

So, what's the deal? If this is government-developed software, why isn't it in the Public Domain? I grant that most recipients would be foolish not to register and get the manuals, but some may not wish to do so.

I also think that the manuals could be included as part of the electronic distribution (they already are, in part) and an interested party could download the bits via FTP or pick them up on a CD-ROM collection without having to bother BRL at all.

Nonetheless, this is all political nitpicking. The system is large, interesting, and relatively freely available. If it looks like your kind of thing, don't hesitate to get a copy!

The BRL materials can be found on (A HREF="" > Start with the README (or NON_USA_README) file. Alternatively, link to the BRL-CAD Web Home Page.