[Update REQ 6846]: global OOGL Grammar

[munzner at cs.stanford.edu]

> we 've found a decription of OOGL file format in geomview manual.
> Thank's to it, we 've written a
> partial parser for OOGL objects. But we have'nt found any global
> description for the whole file format
> (i.e. what does "hdefine" mean ? - for example).
> At the moment we use the grammar explain in section "embedded objects
> and external objects references ")

Ah, I see the problem. The OOGL file format is a *subset* of the
Geomview Command Language (GCL). GCL is documented in a different part
of the manual:
http://www.geom.umn.edu/software/geomview/geomview_9.html#SEC62

'hdefine' is a gcl command, actually one of the more confusing ones.
You use it to bind a "handle" to an OOGL object. Then the value of
that handle can be changed later to another OOGL object, for
fine-grained control over your scene. There's some examples of how to
use handles in
http://www.geom.umn.edu/software/geomview/geomview_8.html#SEC52

You can also look at the source for some of the external modules
distributed with Geomview that use handles. I think trigrp uses them a 
lot. 

Let us know if you have further questions. 

Tamara

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Tamara Munzner	munzner at cs.stanford.edu
http://www-graphics.stanford.edu/~munzner