Subject:
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Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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Newsgroups:
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lugnet.cad.dev
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Date:
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Fri, 1 Oct 1999 15:50:23 GMT
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Viewed:
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914 times
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Jacob Sparre Andersen <sparre@sys-323.risoe.dk> wrote in message
news:FIxHC0.E2v@lugnet.com...
> Lars:
>
> > Leonardo Zide wrote
>
> [...]
>
> > > About that discussion, IMO it would be better to have *everything* CCW
> > > instead of adding a keyword.
>
> This would demand a lot of work before people could start
> using programs that use this fact.
>
> > I agree with John Van in that we need three keywords: CCW, CW, UNKNOWN.
I'm not so sure about this anymore. I think the ideal would be a program that
could change the part files so that they are completely CCW. Using the
raytracing method and enough computer time, he should be able to identify
whether each quad complies with CCW. If a quad doesn't comply, then the
program should rearrange the vertices. If a quad is out of compliance but is
part of a primitive, then the program should mirror and rotate the primitive
so that it complies. The part would then be given the 0 CCW Compliant tag
which would let the rendering program know it could perform backface culling
on that part. Even if the most basic parts, like baseplates, plates, and
rectangular bricks could be brought into compliance, the time savings could be
considerable.
In some cases, like stud2.dat, the primitive file should be altered first so
that it is internally CCW compliant.
If such a utility program could be created, it would take the burden off part
authors to worry about ordering their vertices correctly.
-John Van
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Message has 1 Reply:
 | | Re: CW/CCW, vertex sequence, co-planar, convex, (115kB)
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| (...) If we know that a face is CW, why not change it to CCW ? The most difficult task is to discover the orientation of a face, but once we have that information anyone can change the order of the points and fix the face. (...) This can be done (...) (25 years ago, 1-Oct-99, to lugnet.cad.dev)
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