Subject:
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RE: concave polys and LDraw
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Newsgroups:
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lugnet.cad.dev
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Date:
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Fri, 26 Feb 1999 15:18:21 GMT
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Viewed:
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991 times
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Onyx wrote:
> just realized that LDraw doesn't like concave polys... so now
> i get to hack a test routine into MAX2DAT... anyone done one of these???
> i think i have the formulas for it, so i'll give it a shot...
There was a thread about it back in June 1998 ("LDraw and quads"),
I don't think we ever decided if quads were allowed to be concave.
It seems that LDraw first transforms the 4 vertices and then fills
the four-sided polygon or triangle (if one vertex is in the middle of
the others) now spanned between the transformed vertices. This also
takes care of bow-ties and non-coplanar quads!
The rule may be clear, but is the result desirable?
LDLite and L3P sadly take different approaches to the problem, see the
source files. L3P's L3Input.cpp in
http://www.netby.net/Nord/Mandelvej/Hassing/test/l3dlites.zip
/Lars
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Message has 1 Reply:
 | | Re: concave polys and LDraw
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| (...) unfortunately because of our limitatiions here, i can't illustrate the problem... but if you take a 4-pointed chevron-type shape... sort of like a "V" and hand its points off to LDraw, it comes out as a triange... that's bad if you need the (...) (26 years ago, 26-Feb-99, to lugnet.cad.dev)
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