FORMAT
- The first line of the .reg file contains a comment line of the format #.mode where mode is HETG, HEG, MEG, or LETG.
- The second line of the file contains a comment line of the format #.SRC n where n is the current source id
- For any given source, a maximum of 4 distinct parts (neglecting background) exist. These parts are: zero order, heg arm, meg arm, letg, For any given source, not all of these parts need to be listed.
- Relevant parts of a source are listed one per line. The ordering of the parts depends on the type of data.
  for HEG the parts are
  - zero order
  - heg
  for HETG the parts are
  - zero order
  - heg
  - meg
  for LETG the parts are
  - zero order
  - letg
  for MEG the parts are
  - zero order
  - meg
- All source parts are defined in physical coords
- Parts that belong to a source are identified as follows: physical; <format> ; where <format> is any of the following:
  BOX xcenter ycenter xwidth yheight (optional angle)
  CIRCLE xcenter ycenter radius
  ROTBOX xcenter ycenter xwidth yheight angle
- abbreviations (b)ox, (c)ircle, (r)otbox may be used also
- blank lines are ignored; they may be used to make the .reg more readible to users, but are not used by the code
- a separate source comment line (ie. #.SRC 3) must be supplied before each source included in the region file
- ASCII characters may be in upper or lowercase.
- comment lines beginning with #. are processed as instructions by tg_resolve_events' parser. They are treated as normal comments by other region parsers.
- comment lines starting with a # and succeeded by any other characters are considered 'normal' comments and are ignored by tg_resolve_events' parser

EXAMPLES

a single HETG source, source id of 1

          #.HETG
          #.SRC 1 
          physical; circle 3200 3200 70;
          physical; rotbox 3200 3200 3300 119 -5.3d;
          physical; rotbox 3200 3200 3300 119 5.00d;

two LETG sources, source ids of 2 and 4

          #.LETG
          #.SRC 2 
          physical; c 2000, 2000, 100;
          physical; box 2000, 2000 2000 140;

          #.SRC 4
          physical; c 4000, 4000, 100;
          physical; box 4000, 4000 3500 150;