GMAT Plugins and Extensions

The GMAT source code in the trunk folder contains an atmosphere model – the MSISE90 atmosphere – that was originally coded in Fortran.  The code in GMAT was generated by running the Fortran to C conversion program, f2c, on the original Fortran code.  Future plans for GMAT include adding other models available as Fortran source code using this same approach.  In addition, several of the plugin libraries include code generated from f2c processing of the original Fortran code.  For these reasons, I strongly recommend making f2c available from the start when you prepare to build GMAT.  The system can be built without f2c if you are willing to forego use of these models, but the f2c setup is simple and straightforward, so well worth doing in my opinion.

There are two paths you can follow for incorporating f2c into your configuration.  If you are building with the SPICE library from JPL, the code that you download from JPL includes a version of f2c tailored to use in in SPICE.  The SPICE library also enables several features in GMAT that are useful: the ability to incorporate ephemerides for minor bodies (comets, asteroids, moons, etc) for use in modelling your mission, and the ability to generate a ephemeris file in SPICE format.  In addition, the version of GMAT that undergoes nightly build testing is built with the SPICE extensions enabled, so is more likely to see bug fixes made in a timely manner than are the other versions.  The testing issue is a minor consideration, though; the SPICE enabled code is built from the same code base as the version without SPICE, but with additional features enabled.

Developers that want to use f2c but not SPICE can find a copy of f2c in either GMAT’s build folder for their platform (for Mac or Windows), or as a package for their operating system (Linux).  The platforms that have the library in GMAT’s build folders should unpack the package into the Gmat3rdParty/f2c folder of their build environment.

The SPICE library is available from JPL at the NAIF website.  Download the toolkit for C for your platform, and unpack it into your Gmat3rdParty/cspice (or cspice64 for 64-bit) folder.  Once you’ve done this, you are ready to build GMAT with the SPICE and f2c code enabled.

GMAT is built on several open source packages, set up as described below.  These components play the following roles:

• wxWidgets:  A cross-platform GUI toolkit that provides the windows, frames, text controls, and related components that are assembled to make the GMAT Graphical User Interface.  You’ll need a copy of wxWidgets in order to run the graphical version of GMAT; the console version does not need wxWidgets.
  (URL: http://wxwidgets.org/)
• TSPlot:  The component used to draw XY plots in GMAT.  While this is a separate code base from the rest of GMAT, Thinking Systems has given the GMAT team permission to use the source files in GMAT’s source tree, so there is no separate configuration for this component.
  (http://sourceforge.net/projects/tsplot/)
• f2c:  Several of the models included in GMAT were originally written in Fortran, and converted to C using the f2c conversion program.  GMAT’s source tree includes a minimal version of the files you’ll need for platforms that don’t supply a version of the utility.  Note that if you build GMAT including the SPICE library from JPL, the cspice code includes a customized version of f2c, and a separate copy of f2c is not needed.
  (http://www.netlib.org/f2c/)
• cspice:  The SPICE toolkit from JPL provides utilities for reading and generating ephemerides and other space based data.  GMAT includes the ability to model moons, asteroids and comets from data in SPICE files, and to generate spacecraft ephemerides in SPICE formats.  Configure the SPICE tools to enable this capability.
  (http://naif.jpl.nasa.gov/naif/index.html)

The following paragraphs describe configuration for each of these components.

Setting up wxWidgets

GMAT’s GUI is written using the wxWidgets toolkit, available from wxWidgets.org.  Some operating systems – most distributions of Linux, for example – include options for a precompiled version of wxWidgets.  These precompiled versions are usually built with unicode extensions enabled.  GMAT is not currently unicode compatible, so we’ll build wxWidgets from the source code.  The general procedure is as follows:

1. Download the latest version of wxWidgets 2.8 from wxWidgets.org.  Depending on your platform, you’ll want the following code:
   Windows:  wxMSW
   Mac: wxMac
   Linux:  wxGTK
2. Unpack the code into the Gmat3rdParty/wxWidgets folder.
3. Setup the build files.
   For Visual Studio:  Follow the setup instructions for Visual Studio 2010, and skip the remainder of this section.
   Other compilers and platforms: run the configure command with the OpenGL extensions:
   configure –with-opengl
4. Build the source code:
   make
5. (Optionally) Install the libraries (required administrator rights):
   make install

After following these steps, you’ll have a complete set of wxWidgets libraries for use with GMAT.

In the next post, I’ll discuss f2c and cspice.

The GMAT build files make a few assumptions about the relative arrangement of folders on your computer. This arrangement is, of course, customizable by the developer to meet personal or organizational requirements.  A different arrangement does require that the developer make matching updates to local copies of the build files. The purpose of this entry is to describe a standard arrangement that matches the file arrangement of at least one member of the GMAT development team.

I usually begin by creating a root folder for GMAT development. I have two separate arrangements of the system at my office because of different projects I’m working with; I use TS_Code for most development, and a separate folder for a project built in top of the GMAT code base. For the purposes of this blog I’m using a third root folder, “GmatBlog.” Inside of that folder I have 3 subfolders: GmatDevelopment, Gmat3rdParty, and GmatPlugins. The GmatDevelopment folder holds the code from GMAT’s Subversion repository at SourceForge. Gmat3rdParty holds code and libraries for systems that the GMAT code uses while building: f2c, wxWidgets, pcre, cspice, and so forth. GmatPlugins holds code for plugin libraries GMAT can use – the VF13ad optimizer, the Solar Sail demo code, and a collection of numerical integrators designed by Verner all have folders inside of this one on my development machine. (Truth be told, I tend to have several such folders for different sources of plugin code.)  Once all of the code is in place, the resulting folder layout looks like this:

The next post will explain how to populate the source trees shown here, starting with the Gmat3rdParty folder.  The post after that will describe how to configure and build GMAT on a Makefile driven system (e.g. Linux or Mac, or a Windows machine with GCC installed).

The purpose of this blog is to provide a forum describing approaches to component development  and other programming assistance for the General Mission Analysis Tool (GMAT).  The materials here will include discussions about extensions to the tool and ways to use GMAT’s engine in projects outside of the main GMAT system.  The first few postings will look at general configuration issues, followed by discussion of extensions through plugins and related projects.  Here is my current list of items for discussion:

• How to build GMAT (probably several entries, covering basic setup followed by overviews of building on Windows, Linux, and Mac)
• GMAT’s plugin architecture
• Connecting to the GMAT engine from MATLAB
• Developer Playtime Projects
• Building a Qt based GUI for GMAT

Please make suggestions for additional items in the comments to this entry, and I’ll add the items to the list!