gda@creare.uucp (Gray Abbott) (04/23/86)
Can anyone tell me how to do "swept surfaces". I'm working
on a CAD-type system to be used as the front end of a new
computational fluid dynamics program and would like to provide
a tool which makes it easy to construct curved pipes and ducts.
The idea is to take a surface patch and sweep it along a "directrix"
curve, to create the pipe, or whatever.
I've seen some references which mention keeping the swept object
fixed in the Frenet frame of the directrix, but this doesn't seem
to work the way I want it to; the swept patch rotates in ways that
do not agree with intuition. What appears to be desirable is that
the swept patch rotates about the binormal vector at any point
along the directrix, but I haven't been able to express this
mathematically. Also, I'd like to be able to calculate just the
position of the patch at the two endpoints of a cubic section of
the directrix.
Does anybody understand what I'm talking about? Do you know how
it's done? Can you at least give me a pointer to a good reference
on it (I've got Faux and Pratt, but it doesn't address this problem
in detail).
Thanks in advance.
Gray Abbott
Creare Inc.
Hanover, NH
{...dartvax!creare!gda}