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 CAD / Development / 3008
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Subject: 
Re: Hidden surface removal, and vertex order in part/primitive DAT files
Newsgroups: 
lugnet.cad.dev
Date: 
Mon, 4 Oct 1999 04:19:59 GMT
Viewed: 
724 times
  
Steve Bliss wrote in message <37f6c258.270062819@lugnet.com>...
On Sat, 2 Oct 1999 14:15:02 GMT, "Gary Williams" <graywolf@pcpros.net>
wrote:

My LDraw folder has seven DAT files with '0 CW*', none with '0 CCW*', and • 30
with '0 not CW*'.

The seven '0 CW*' files are:

...
PARTS\578.DAT

Note that 578.DAT contains a suspicious comment :)

578 is compliant because it contains *only* subfile references, which have
been verified to not mess up (C)CW-ness.  But that doesn't mean the
*subfiles* are compliant.  It also assumes the compliant subfiles are
oriented the way the author (me) expected them: cylinders' surfaces facing
outward, disc facing upward.

Does that mean if a program would find the CW directive it can assume that
every-thing in this file is compliant? E.g. the program would not have to
test if possible included parts are compliant, but assume that they are
since the parent is complient. I understand that this would be valid when
drawing the specific compliant part only, not if the included part is used
in a different part which is not compliant!

Mike



Message has 2 Replies:
  Interpreting the proposed FACE meta-command
 
Michael Lachmann wrote in message ... (...) Here's my take on the matter. The meta-command: 0 FACE <CW|CCW|DS|UNKNOWN> ...should only be used to indicate the order of the vertices of the polygons _in the file that contains it_. If A.dat has a '0 (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)
  Re: Hidden surface removal, and vertex order in part/primitive DAT files
 
(...) No (like Gary said). Two reasons: 1. The 0 FACE directive would be an operative switch, not a global setting. This is convenient, but it is also necessary in some cases. Most importantly, it would allow the 0 FACE meta-statement to appear (...) (25 years ago, 4-Oct-99, to lugnet.cad.dev)

Message is in Reply To:
  Re: Hidden surface removal, and vertex order in part/primitive DAT files  [DAT]
 
(...) 578 is compliant because it contains *only* subfile references, which have been verified to not mess up (C)CW-ness. But that doesn't mean the *subfiles* are compliant. It also assumes the compliant subfiles are oriented the way the author (me) (...) (25 years ago, 3-Oct-99, to lugnet.cad.dev)

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