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Subject: 
Re: Problem with Primitive Generator
Newsgroups: 
lugnet.cad
Date: 
Tue, 29 Jan 2008 06:11:00 GMT
Viewed: 
3456 times
  
In lugnet.cad, Philippe Hurbain wrote:
I think a solution that mostly works was invented around this
time frame:

  http://news.lugnet.com/cad/dat/parts/?n=3375

Instead of using cylinder primitives with an optional line at one end
that expects to be mated with a similar cylinder primitive, you use
optional lines at both ends that share the work by dividing the curve
angle in half.  This puts the optional line control points on the
tangent plane, which allows you to mate a cylinder primitive with
another cylinder or with a quad in the tangent plane.
Yes, that's the way cylinder primitives are done, and it seems to work very
well. I think other primitives could be improved that way.

But it doesn't
work for S curves made of two cylinder primitives mated in the
opposite direction.

That case is not that bad - the angle where the middle line appears is divided
by two, so it is an improvement. Moreover the line is better accepted in that
case since the surface is locally tangent to the eye direction.

I don't think this was ever implemented for cylinders, but it might
have made it into some of the sphere primitives.  More info here,
with pictures and some discussion of the primitive generator.

  http://news.lugnet.com/cad/dat/parts/primitives/?n=350&t=i&v=a

This thread perfectly describes the problem. Unfortunately Paul didn't update
PrimGen...

Philo

I believe this was corrected back in November of 2003. There have been other
updates to PrimGen since then.
Look under options, 'original style cyli and cones'.
I do not recall a discussion where it was ever decided to change to the "newer"
configuration so I set the option 'on' at start. (it does not save this setting)

Cheers,
Paul Easter

http://www.geocities.com/pneaster/prim-gen.htm



Message has 2 Replies:
  Re: Problem with Primitive Generator
 
Paul, (...) Shame on me for these words! I should wear better glasses. (...) Thanks a lot, Paul. Indeed it solves that issue. The official cylinder primitives are now new style so I guess the option could be set to off now (though most cone (...) (16 years ago, 29-Jan-08, to lugnet.cad)
  Re: Problem with Primitive Generator
 
(...) Paul! I'm glad you're still around. ya know I'm still struggling with the issues listed here: (URL) chance for an update? bye, w. (16 years ago, 29-Jan-08, to lugnet.cad)

Message is in Reply To:
  Re: Problem with Primitive Generator
 
(...) Yes, that's the way cylinder primitives are done, and it seems to work very well. I think other primitives could be improved that way. (...) That case is not that bad - the angle where the middle line appears is divided by two, so it is an (...) (17 years ago, 26-Sep-07, to lugnet.cad)

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