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Subject: 
Re: Some Words To BFC
Newsgroups: 
lugnet.cad.dev
Date: 
Wed, 5 Apr 2000 21:26:31 GMT
Viewed: 
2162 times
  
I need to digest this.  I'll respond tomorrow.

Steve

In lugnet.cad.dev, John VanZwieten wrote:


Leonardo Zide <leonardo@centroin.com.br> wrote in message
news:38EB3EB8.D81D2CD7@centroin.com.br...
John VanZwieten wrote:

If I've misstated anyone's position, or if I'm missing some major issue • here,
I apologize, and please enlighten me :)

  I'd like to have all parts compliant by making a second copy of the
primitives that can't be inverted instead of using "0 INVERSE" commands.


Hey, this idea might work in conjuction with your program that fixes parts.
If we had a parallel directory (/pi/?) with a copy of each primitive with the
winding opposite, then whenever the fixer program finds a primitive which
needs to be inverted, it could just add "pi/" to the primitive name in that
line.  Part authors wouldn't have to mess with this; it would all be done in
the post-processing stage.

So here's my suggestion for a simplified BFC regime:

1.  We handle BFC certification at the parts level (/parts directory), and
fix all the parts at "once."  New parts would be fixed before they are
released.  By "fixed," I mean that all outward faces are wound CW, and a
second set of primitives are used to model "inner" faces.  Cases of
double-sided quads would have to be ferreted out and fixed.

It seems to me that Leonardo's program is up to this task, perhaps with a
little improvement.

2.  If the rendering program can assume that all parts are correctly CW, then
it doesn't have to waste time checking for certification, winding direction,
BFC on/off, etc.  If a part is used in a model file with an inverted matrix,
then that part must be CCW, and the rendering engine can account for that.
As Michael pointed out, primitives, quads, etc. used in a model cannot be
BFC'd.  Likewise, mock-ups need to be kept out of the /parts directory so
they won't be BFC'd either.

So what do you think?  Can this be done?  Are there contingencies not
accounted for here?

-John Van

P.S.  Please note that I am not in any way "dissing" all the work put into
the BFC proposal.  Without it, Michael probably wouldn't have implemented
BFC, and we still be talking only theoretical.  I simply think that given
what we found in MLCad and given the impressive fixer programs we now have to
work with, this way seems to offer the greatest potential improvement and the
least complexity.







Message has 1 Reply:
  Re: Some Words To BFC
 
Steve Bliss <blisses@worldnet.att.net> wrote in message news:4qbnescr7hii5bq...4ax.com... (...) I hope it doesn't cause indigestion :-) -John Van (25 years ago, 5-Apr-00, to lugnet.cad.dev)

Message is in Reply To:
  Re: Some Words To BFC
 
Leonardo Zide <leonardo@centroin.com.br> wrote in message news:38EB3EB8.D81D2C....com.br... (...) here, (...) Hey, this idea might work in conjuction with your program that fixes parts. If we had a parallel directory (/pi/?) with a copy of each (...) (25 years ago, 5-Apr-00, to lugnet.cad.dev)

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