Subject:
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Re: Hidden surface removal, and vertex order in part/primitive DAT files
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Newsgroups:
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lugnet.cad.dev
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Date:
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Sat, 2 Oct 1999 07:45:12 GMT
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Viewed:
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625 times
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What if say a complient file contains anything starting with "0 CW". Any
program dealing with this information could just scan for "0 CW*". We also
could use a tag "0 AW*" if why ever the orientation is not clock-wice but
anti-clockwice .... I think a program could deal with that also (just the
sign is different !?).
So if we can define this as a standard, I will build this into MLCad and
Version1.5 and above could make use of this feature (which should speed up
drawing a little bit). By the way any idea how many parts already have this
tag?
Mike
Leonardo Zide wrote in message <37F52F67.5158EEF2@centroin.com.br>...
> Gary Williams wrote:
> >
> > I'd vote for CW for two reasons:
> >
> > 1) 'Clockwise' is shorter than 'counterclockwise'.
>
> I can't argue with that :)
>
> > 2) CW is used more often than CCW in rendering applications (to my
> > knowledge) because the normal of a CW-defined polygon points outward,
> > instead of inward.
>
> No way ! The front faces are CCW in 3DS Max, and quoting the OpenGL
> 1.2 specs. for glFrontFace() "mode: Specifies the orientation of
> front-facing polygons. GL_CW and GL_CCW are accepted. The initial value
> is GL_CCW."
>
> Just use your right hand instead of the left and you'll get outward
> normals. Do things just like when you try to imagine the signal of the
> cross-product between two vectors.
>
> > I'd also suggest that the standard comment read '0 CW' instead of '0
> > CW-compliant'. Less chance for typographical error if the file was • created
> > manually.
>
> You can also save a few bytes using only 0 (C)CW.
>
> Leonardo
>
>
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