Subject:
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Re: Question about generating curves
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Newsgroups:
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lugnet.cad.dev
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Date:
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Wed, 10 Jan 2001 04:20:59 GMT
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Viewed:
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417 times
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----- Original Message -----
From: "Franklin W. Cain" <fwcain@yahoo.com>
To: <lugnet.cad.dat.parts@lugnet.com>; <lugnet.cad.dev@lugnet.com>
Sent: Tuesday, January 09, 2001 9:38 PM
Subject: Re: Question about generating curves
> (Note: Please follow-up to ".cad.dev".)
>
> In lugnet.cad.dat.parts, Tony Hafner writes:
> >
> > What is an optional line? These seem to be used for modeling curves,
> > but I don't have a clue how to use them.
>
> > While I'm asking, what is a BFC statement?
>
> "BFC" = "Back Face Culling", something about deleting/not rendering
> the "back faces" (i.e., the sides concealed by the rest of the model,
> or otherwise not viewable). Someone else will have to explain better,
> this is as much as I understand about BFC.
Back faces are polygons that are facing away from the viewer, and therefore
not visible. Since there is no point in rendering a polygon that can't be
seen, most rendering algorithms will try to ignore these polygons so they
can render twice as fast. This process is called backface culling.
Unfortunately it's extremely difficult to determine which polygons are
facing away from the viewer if they haven't all been defined consistently
(i.e., the vertices of the polygons must all be defined in clockwise or
counterclockwise order in the part DAT files). Thus the ongoing BFC
certification process for part files. New part files are checked for
consistency and then certified so they can be rendered faster.
-Gary
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Message is in Reply To:
 | | Re: Question about generating curves
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| (Note: Please follow-up to ".cad.dev".) (...) OK, first you need to bear in mind that LDraw does _NOT_ draw true curves, it draws _angles_. If you have enough angles in a line, from a sufficient distance, this angled line will _appear_ to be a true (...) (24 years ago, 10-Jan-01, to lugnet.cad.dat.parts, lugnet.cad.dev)
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