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Here's my answers to your questions - hopefully someone else can
expand them.  

2) Yes.  I assume by "altering its transformation" you mean applying a
transform to it, since only insts have associated transforms.  There
are routines called GeomTransform and GeomTransformTo.  The syntax is:

GeomTransform(Geom g, Transform T);

For everything except insts, they work by changing the points of the
objects, and in fact give the same results as:

HPoint3 *points;
Geom g;			/* Original geom */
Transform T;		/* Transform you want to apply */
points = PointList_get(g, TM_IDENTITY, POINTLIST_SELF);
HPt3TransformN(points, points, PointList_length(g));
PointList_set(g, POINTLIST_SELF, points);

although they are written without using the pointlist library (mostly
because the pointlist library wasn't written then).  For everything
except insts, GeomTransform and GeomTransformTo do the same thing.
GeomTransform is probably the more logical choice (see below).

For insts, GeomTransform postmultiplies the given inst by the given
transform.  GeomTransformTo replaces the matrices with T.

I remember looking at the code for BBoxTransform and thinking that it
looked like it did someting differently, but I didn't look into it in
detail and i doubt you'll ever want to use it.

3) <apology>

4) Just to make the problem even worse - the program would also have
to recognize and cope with handles and files, eg:

(geometry thing : myhandle)
(geometry otherthing < dodec.off)

5) I've thought about doing similar things for normals and colors.
One problem is that the normals and colors are sometimes by face,
sometimes by point, and sometimes not there at all.  One short-term
goal would be a function which would take a function pointer as its
arguement, then would call the function with each point of the geom.
The function would be responsible for coming up with an appropriate
color based for each point (presumably based on the location of the
point).  Would this be of any help?  


Celeste Fowler			email:  fowler at geom.umn.edu
The Geometry Center		phone:  ((555) 555-5555
1300 South Second Street
Minneapolis, MN  55454

  • References:
    • Arrgh!
      • From: "Mr. R.J. Morris " <rmorris at uxb.liv.ac.uk>
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