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From: peterf@kuling.UUCP (Peter Fagerberg)
Newsgroups: comp.graphics
Subject: Help needed - 3D surface problems
Message-ID: <309@kuling.UUCP>
Date: Sun, 24-May-87 13:33:48 EDT
Article-I.D.: kuling.309
Posted: Sun May 24 13:33:48 1987
Date-Received: Tue, 26-May-87 02:00:05 EDT
Organization: DoCS, Uppsala University, Sweden
Lines: 35


I am currently working on a project with lots of graphics and since
I'm not really a graphics expert, like most of you people, I was
wondering if you could help me with a few pointers in the right
direction.

Here are my two problems:

Problem #1 involves adjusting the values of a set of discrete points
generated by an industrial scanning machine. Maybe you've heard about
these machines; car designers often make a prototype of a new car
model in clay and that model is scanned so that you can work on it
with CAD-computers. The problem is that the scanning-machine uses a
little needle with a round point that gives a certain (known) offset
to the surface being measured. In order to adjust the values I want to
approximate how the surface looks in a ceratin point by looking at its
neighbours (2,4 or 8 of em'), construct the plane in that point and
find the normal vector to that plane. If I know the normal
vector, all I have to do is move the point 'offset' millimeters in
that direction.

Problem #2 is a little harder (I think :-)). I need an algorithm,
preferably fast, that measures the distance between a point in space
and a Bezier or B-spline surface.

                             Thanks in advance,

Please E-mail me directly and if anyone else is interested - send me a
little note (E-note? :-)) and I'll be glad to summarize.

-- 
==============================================================================
Peter Fagerberg             UUCP: {seismo,enea,mcvax,decwrl,...}!kuling!peterf
Applied Computer Science    ARPA: kuling!peterf@sismo.css.gov
Uppsala University          Analog: +0046 18-128286 or 8-102927