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Subject: 
Re: Gappy Spheroids?
Newsgroups: 
lugnet.cad.dev
Date: 
Wed, 6 Sep 2000 22:28:44 GMT
Viewed: 
525 times
  
"Dave Schuler" <orrex@excite.com> wrote in message
news:G0HFCH.Dz9@lugnet.com...
In lugnet.cad.dev, Travis Cobbs writes:
"Dave Schuler" <orrex@excite.com> wrote in message
news:G0H8D0.n04@lugnet.com...
Playing around with part-authoring, I've been trying a few different • methods
of generating pseudo-curved surfaces.  I've noticed that different • "facets" of
such an approximate curve render with gaps between them in L3P and • L3Lab,
even
when two adjacent facets share an actual edge.  What causes this gap to
appear, and is there anything that can be done about it?
  I'm not so worried about the faceted appearance of the approximated • curve;
in fact, I think that's kind of cool.

I'm not sure I understand what you are saying completely, but I'll give • an
explanation based on what I think you're saying ;-).  The gaps aren't in
your approximation; they're where your approximation meets one of the
primitives, (cone, cylinder, sphere, etc) which has been replaced by L3P.

  I suppose I could have been more specific in my explanation.  The gaps
aren't occuring between my approximate curve and a primitive; they're • occuring
at the joints between facets of the approximate curve.  An example of the
faceting can be seen here (I apologize for the inclusion of a clone, but • it's
the only example I have at the moment):

http://members.bellatlantic.net/~drteeth1/hawk.jpg

  The gapping is hard to see in this image, but it tends to occur along • the
seem between longitudinal facets of an approximated curve.  Can you think • of a
way to remedy this?

You're right; it's hard to see.  In fact, I can't see it at all, but I'll
take your word for it.  The only two causes I can think of are that the
spheroid is made up of multiple "parts" which L3P treats as such and shrinks
to produce inter-part seams (the seam width option), or there really are
gaps in the pieces.  (Note, I'm not saying these are the only possibilities,
just that they're the only ones I can think of.)

If it is the former, the gaps should go away if you set the seam width
option of L3P to 0 (don't know off the top of my head the actual option
name).  While this seems like an unlikely cause, it would certainly be easy
to test.  If there really are gaps in the quads you generate, they should
show up in all renderers (POV via L3P, L3Lab, LDraw, LDView, etc.).  Make
sure to set the seam width to 0 on those renderers that support this option.

--Travis Cobbs (tcobbs@san.REMOVE.rr.com)



Message has 1 Reply:
  Re: Gappy Spheroids?
 
I forgot to mention. If you are examining a piece, it is usually much easier to determine surface characteristics (or flaws) if it is opaque. --Travis Cobbs (tcobbs@san.REMOVE.rr.com) (24 years ago, 6-Sep-00, to lugnet.cad.dev)

Message is in Reply To:
  Re: Gappy Spheroids?
 
(...) I suppose I could have been more specific in my explanation. The gaps aren't occuring between my approximate curve and a primitive; they're occuring at the joints between facets of the approximate curve. An example of the faceting can be seen (...) (24 years ago, 6-Sep-00, to lugnet.cad.dev)

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