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Documentation Table of Contents

PLEASE NOTE: On Mac OS X, you MUST be running X11 for Syzygy graphical programs to work.

For complete functionality, Syzygy programs have to be run in Cluster Mode. However, it's often more convenient to run a single instance of a program in Standalone Mode. The advantage of Standalone Mode is that no Syzygy server or supporting programs are required; the main disadvantage is that standalone programs can't load input device drivers, but must instead use the tracking simulator interface (although we plan to fix this in version 1.2).

How a Program Determines Whether to Run in Standalone Mode

When a Syzygy program is run, it goes through the following decision process to determine whether or not it is running in Standalone mode:

1. It determines the current user's system name (as reported by the native operating system).

2. It looks for a corresponding Syzygy login file (described in Creating a Cluster: The Syzygy Login Files.

3. If this file exists and specifies that the user is logged into a Syzygy server, then the program attempts to connect to the server.

4. If it connects successfully, the program is running in Cluster Mode.

5. Otherwise, the program is running in standalone mode.
   You can force programs to run in standalone mode by issuing the "dlogout" command. This modifies your Syzygy login file to specify that you are not logged into a server.
   If it is running in standalone mode, your program will print (among many other lines of start-up information) the following line:

     szg:CRITICAL: my_program_name running standalone.
   

   
   Test standalone mode by running "hspace", a master/slave sample application, and "parade", a distributed scene graph sample application. These are both contained in the base Syzygy distribution and can be downloaded or compiled as described in Getting the Software. For more information on the different styles of Syzygy programs, please consult the Introduction to Syzygy programming.
   When running "hspace" in standalone mode, something looking like a green spiderweb should fill the window. There will also be a small overlay window in the lower right corner showing the tracker simulator interface, whose operation is described in this chapter. When running "parade", you will see a collection of collection of virtual humans marching across the screen, again with the tracker simulator in the lower left corner. More information about these and other sample applications is included in Example Programs.

Configuration Information in Standalone Mode

When a Syzygy program starts, it needs to be configured with information regarding where it should find data files, where it should place its graphics screen on the desktop, and where sound and texture files exist, among other things. In Standalone Mode this information is read from an XML file. By default, the program looks for a file in the current working directory named either szg_parameters.xml or szg_parameters.txt, in that order. However, the file name can be overriden by passing a special command line argument to the program, for example:

  my_program_name arg1 arg2 -szg parameter_file=szg_anaglyph.txt
  my_program_name arg1 arg2 -szg parameter_file-szg_virtualcave.txt

Note that any arguments prefaced by -szg are interepreted as special Syzygy arguments and are removed from the argument array and processed by the Szygyy libraries before the array is handed to the application code.

If the program cannot open the specified config file it will check to see if the environment variable SZG_PARAM is set; if so, it will use SZG_PARAM's value as a file name and try to load that file.

For a discussion of the format of the information in this file, see the System Configuration chapter. The only aspect of this format that is specific to Standalone Mode regards the specification of the computer name. In Cluster Mode, each computer-specific or local parameter must be defined using the name of the computer, e.g.

  my_computer SZG_DATA path C:\Data

In Standalone Mode, on the other hand, the value NULL can be substituted for the computer name (since there's only one computer under consideration):

  NULL SZG_DATA path C:\Data

If a program requests the value of a configuration parameter and it is not present in the file, the program will try to get it from an environment variable whose name consists of the parameter's group and name. For example, if the program wants the value of the parameter SZG_DATA/path, it will look for an environment variable named SZG_DATA_path containing the value.

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