Subject:
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Re: Comprehensive meta-command list
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Newsgroups:
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lugnet.cad.dev
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Date:
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Fri, 8 Oct 1999 15:37:27 GMT
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Reply-To:
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Rui.Martins@link.^spamless^pt
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Viewed:
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493 times
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On Fri, 8 Oct 1999, Lars C. Hassing wrote:
> Gary Williams wrote in message ...
> >
> > Lars C. Hassing wrote in message <939367581.966085@ns.cci.dk>...
> > > But I admit that the idea that FACE (C)CW only affects the triangles/
> > > quads of the current file, and that INVERT only affects subfiles
> > > is much easier to comprehend and thus is a better solution.
> > > /Lars
> >
> >
> > In addition to being easier to comprehend, it has the advantage that each
> > part and primitive file only has to concern itself with its own vertex
> > order, and is not dependent on any other file. This is the primary benefit.
> > This makes parts and primitives truly modular and interchangeable.
>
> "...not dependent on any other file..." Well, I hope you agree that files
> depend on the inside/outside-definition of subfiles?
> Otherwise a file wouldn't know whether or not to use the INVERT.
> /Lars
I think that the ideia here is:
- Assume any file you reference as CCW WINDING (assuming CCW as default)
- Assume any file as it's polygonal faces facing outward (if applicable)
- Every time you want a diferent orientation, just use the INVERT TAG
- If any file, internally has a diferent winding, than, internally it
will have a CW TAG were needed.
if the file has no CCW/CW/CLIPPING TAG, than the INVERT TAG is redundant,
but can be used, to enable the subfile to be enhanced in the future.
P.S.
I understood that the INVERT TAG is meant for something diferent to what I
was thinking.
I think this is what is meant:
Y axis
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_-|---__
/ | \
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------+------------------------------- X axis
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\__|_____/
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(top view)
Supose this is an eliptical cylinder (no bases) with a dent in the bottom
part, NOT centered in Origin.
Now if you MIRROR trough the Y axis using the matrix in a reference, than
all the face normals would point inward (assuming that in the beginning
they pointed outward). So the faces (polygons) would be clipped when
looking from the outside.
No if there is really such a part or primitive, maybe it's better to
supply that (possibly unique) primitive already in an inverted form.
little has to be gained, except program complexity.
This all falls apart if there is use of such parts/primitives in great
extent.
NOTE: if the cylinder didn't have the dent, it would suffice to rotate it
+180 or -180 degrees.
Rui Martins.
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Message is in Reply To:
 | | Re: Comprehensive meta-command list
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| Gary Williams wrote in message ... (...) "...not dependent on any other file..." Well, I hope you agree that files depend on the inside/outside-definition of subfiles? Otherwise a file wouldn't know whether or not to use the INVERT. /Lars (25 years ago, 8-Oct-99, to lugnet.cad.dev)
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