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From: tima@agora.uucp (Tim Anderson)
Newsgroups: comp.graphics
Subject: Re: Shrinking Bezier curves
Summary: you can 'kludge' it, like IGES!
Message-ID: <1990Jul27.155626.9205@agora.uucp>
Date: 27 Jul 90 15:56:26 GMT
References: <1990Jul27.063052.9708@allgfx.agi.oz>
Reply-To: tima@.UUCP (Tim Anderson)
Organization: Betazoid Central
Lines: 21

By now you probably know that you can't do this, but you can get 'close'...

Another approach is to do what the IGES spec. does, leave the original 
curve - but put in an 'offset' value. So when you go to re-create these
curves, you calculate the point and tangent vector then offset the 
appropriate distance. This approach leads to a 'true' offset (or as true
as you can get!) with the benefit of not having to drain your brain to
figure out a way to calculate a real approximation. This is the approach
that I am taking to offset NURBS in our CAM system, simply because
generating approximate offset NURBS is a nightmare AND I have to get this
done before September...

see ya' at IMTS!

tima@agora.hf.intel.com
tektronix!tessi!agora!tima

PS Don't forget that offset curves have a nasty habit of backing up on 
   themselves. This is called 'gouging' in the CAM business. Let's just
   hope that no one wants to make anything that has too sharp a curve in
   it! ;-)