triangle groups module

[munzner]

Trigrp (the triangle groups external module) uses geomview for the
window of tesselations but handles the window for the small triangle
on its own.  (The program was originally written a few years ago and
only the tesselation part of it has been ported to geomview.)  More
specifically, trigrp uses the OOGL libraries for drawing the triangle
window but handles raw GL events (like tracking the mouse) on its own.

Geomview documentation is in the doc subdirectory.  The most basic
piece of documentation is overview. oogltour is a tutorial intro to
the OOGL file types while oogl.5 is the complete OOGL file type
reference guide.  geomview.5 is the geomview command language
reference guide.  There is no tutorial for the command language and/or
making external modules yet.

The command language is what modules use to communicate with geomview.
The OOGL file syntax is used by some commands like "geometry".  A
basic rule of thumb is: if something is wrapped in parentheses it's
command language, if it's wrapped in braces it's OOGL file language.

Modules read from stdin and write to stdout. Geomview deals with
hooking up the pipes correctly. Geomview knows about an external
module via the command "ui-extern-program <string> <pathname>". In
data/.geomview, the pathnames are short because geomview looks in the
GEOMBIN directory ($geomroot/bin/sgi), where all of the external
modules we distribute can be found.

One of the nice things about modules just writing to stdout is that
it's easy not only to debug them but also to see what somebody else's
module is doing: just start it up from the shell to see exactly what
it's sending to geomview. Some modules like nose don't do much that's
interesting without input from geomview, but trigrp doesn't need any
additional information to work.

Juicy parts of the documentation:

geomview.5: 
"geometry" is the most important command you'll use.
if you use handles you'll also need "read" (see below)

oogltour and/or oogl.5: 
the part about the file type you're using.

(The basic types are quadrilaterals, polyhedral structures with
connectivity information, rectangular meshes, polynomial patches, and
vectors. The complex types are lists (just a collection of objects)
and insts, which allow you to apply 4x4 transform(s) to another
object.)

oogl.5:
The stuff you might need to understand in the oogl.5 document is how
handles work if you want to use them. They're a way to name a part of
a structure so that when just that part changes you don't have to
resend the whole thing, just the part.

Hope this helps,

Tamara Munzner          ((555) 555-5555
munzner at geom.umn.edu    The Geometry Center