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From: milo@ndmath.UUCP (Greg Corson)
Newsgroups: comp.graphics
Subject: How do I handle this kind of model??
Message-ID: <1131@ndmath.UUCP>
Date: 18 May 88 00:38:55 GMT
Organization: Math. Dept., Univ. of Notre Dame
Lines: 43

I have a rather odd type of 3D model I need to represent and I'm
taking suggestions on how to do it.  The objects being modeled
are not so strange...but the type of calculations I need to do on
them may be a little odd.

I need to model various types of smooth surfaces such as rolling
hills, car bodies, human faces etc.  The pictures produced from
the models need to be hidden surface but WILL NOT be shaded in
any of the usual ways.  The shading will be very simple...if an
object is defined as "blue" it will be the same shade of blue 
all over.  The odd part is that the rendering routine will need 
to look for sudden changes in the objects contours (or places
where one object overlaps itself or another of the same color)
and draw "feature lines" at those places.  For example, if you
were modeling a piece of metal with a very gentle bend, only the
outer edges would be drawn in as black feature lines....however
if you had a piece of metal with a sharp 45 degree bend in it
there would be a black like at the location of the bend.

The idea is to produce pictures that resemble hand-drawn "cell"
animation but are actually based on 3D models.  There will be
no light source-based shading AT ALL.  I just need a way of
modeling surfaces where it is easy to locate the edges of objects
and locations where the shape of the object changes suddenly.

Some type of Z buffering system is a good possibility, but if
anyone can think of a simpler way....

If you have any ideas, please try to write me at my USENET
mailbox...I don't get to read comp.graphics often enough to avoid
missing things.

It would be nice if the modeling technique could actually model
surfaces with some kind of 3D spline/patch based system.  Although
a technique which uses polygons would be ok too.

Thanks!!!

Greg Corson
19141 Summers Drive
South Bend, IN 46637
(219) 277-5306 (weekdays till 6 PM eastern)
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