Path: utzoo!yunexus!ists!jarvis.csri.toronto.edu!rutgers!ucsd!ogccse!blake!milton!uw-beaver!sumax!nwnexus!tim
From: tim@nwnexus.WA.COM (Tim Anderson)
Newsgroups: comp.graphics
Subject: NURBS, interpolating them with lower degree NURBS
Summary: need hints, neophyte, ignoramous, spam-head
Message-ID: <206@nwnexus.WA.COM>
Date: 16 Nov 89 17:14:30 GMT
Article-I.D.: nwnexus.206
Reply-To: tim@nwnexus.UUCP (Tim Anderson)
Distribution: comp.graphics
Organization: Northwest Nexus Inc.; Seattle, WA
Lines: 32


I, ever humbled, ask the net another set of questions...

I want to turn big ugly NURB's (with degree <= 20) into lots of nice
quick-to-draw peicewise cubic rational Bezier's. (What I *really* want
is to be able to display and compute tangents and normals at blinding
speed and the easiest way is to convert it all to rational cubic Bezier's
then hard code various transforms, no? I have been using Mssr Lee's zippy
method of computing points and tangents, but the amount of information that
I have to have to use it tends to slow things down. Yes, I am working in
the REAL world with finite memory and slow hard drives.).

First you bang Oslo's algo over them till they look like Bezier's. Now we
have lots of monsterous degree Bezier's around. Do I just cut those into
little sections and then do a bunch of curve fitting with cubic Bezier's?
Seems like there would be a 'better' way of doing this than that...

I was thinking of maybe cutting them up, then doing a degree reduction on 
each section till the answer falls out. This is a bit more accurate? but 
incredibly time consuming (no doubt). Any hints for this poor old soul 
wandering aimlessly in NURBS land? I have every book I could possibly find
and a few billion articles from CAD, CAGD, CG&IP, etc, etc... so if one of
you person's of infinite wisdom could point me in the correct direction, I 
would personally worship you as a diety.

Thanx!
tim@nwnexus.wa.com

PS: If you are selling a NURBS package, please DO NOT foist a bunch of sales
stuff onto me. Not only can I NOT afford it, I do not want it! (with all due
respect to those nice folks in UTAH).