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From: hugo@hydra.unm.edu (patrice cummings)
Newsgroups: comp.graphics
Subject: polygon orientation in DXF?
Date: 16 Apr 1993 13:58:01 GMT
Organization: University of New Mexico, Albuquerque
Lines: 21
Message-ID: <1qme19INN82m@lynx.unm.edu>
NNTP-Posting-Host: hydra.unm.edu


Hi.  I'm writing a program to convert .dxf files to a database
format used by a 3D graphics program I've written.  My program stores
the points of a polygon in CCW order.  I've used 3D Concepts a 
little and it seems that the points are stored in the order
they are drawn.

Does the DXF format have a way of indicating which order the 
points are stored in, CW or CCW?  Its easy enough to convert,
but if I don't know which way they are stored, I dont know 
which direction the polygon should be visible from.

If DXF doesn't handle this, can anyone recommend a workaround?
The best I can think of is to create two polygons for each one
in the DXF file, one stored CW and the other CCW.  But that
doubles the number of polygons and decreases speed...

Thanks in advance for any help,

Patrice
hugo@hydra.unm.edu 
