getting started with geomview

[mbp]

Seth,
    Sorry to be so slow to respond to your question.  The problem is
that it actually requires some thought, :-).
    A very quick answer is that I believe it is possible to do what
you want with Geomview, although the result will probably look and
feel a little awkward.  It might be good enough for prototyping, but
if you want to actually use it very much you're probably better off
using Inventor or GL.  The main problem is that programmed interaction
like what you describe (e.g. having a line move in respond to the user
dragging a point) is not Geomview's strong point.
    You'd have to write an external module which listens for drag
events on the desired object by sending Geomview a "(interest
(xform-set AAA))" command, where AAA is the name of the object.  (It
is possible to do this for more than one object at a time.)  Your
module would then use the matrix returned by the "(xform-set AAA ...)"
commands it receives from Geomview to update the position of the
object's dual.  You have to be sure to avoid infinite loops, which
are easy to create if your module is both moving and listening for
drags on the same object.
    I'll try to put together a sample script to do a crude version of
your idea in the next few days and will send it to you.  In the
meantime, if you want to play around with the commands above, do the
following: Invoke geomview as "geomview -c -", which tells it to read
commands from stdin.  Then load an object, say "dodec.off".  Then type

    (interest (xform-set "dodec.off"))

followed by a newline in stdin to geomview.  Now select the dodec.off
object (right mouse double-click on it, or select it in the browser in
the main panel), and then drag it around.  You should see commands of
the form

    (xform-set dodec.off   MATRIX)

spew forth in your terminal window.

--Mark