Subject:
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Re: Smooth surfaces
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Newsgroups:
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lugnet.cad.ray
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Date:
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Thu, 20 Sep 2001 22:18:55 GMT
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Viewed:
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692 times
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Lothar Teichert wrote...
> I think the following is of interest in this newsgroup:
> L3P generates "meshes" of parts from Ldraw, that are not in LGEO and not
> covered by other special handling.
> Meshes consist of triangles and there are creases, if triangles from
> different planes collide.
> I remembered the notion of "creaseangle" in VRML and adopted it to
> replace the triangles of L3P by "smooth_triangles" (see POVRAY-Help for
> explanation, some computing of normal directions is necessary).
> Resulting surfaces look more smooth though you may not expect too much.
> See some examples at http://members.aol.com/elferwette/LDraw/index.htm.
> Is it worth to ask Lars Hassing for integration in L3P, e.g. controlled by
> commandline parameters?
Hi and welcome Lothar,
Yes, I think it is worth to ask him :-)
What a brilliant idea. I had completely forgotten about the smooth_triangle.
The one example you provide looks very nice.
Do you have more examples?
Do you have any examples where it doesn't work well ?
(It "removes" the white grille on 3010p20w.dat Brick 1 x 4 with Town Car White Grille,
and the mouth of 3626bp01.dat Minifig Head with Standard Grin Pattern)
Which angle is best for a default ?
(I found that 155 works well.
If smaller, some slope bricks get undesirably smoothed.
I think the angle should be just below 157.5 degrees,
which is the angle between surfaces of a cylinder made of 16 surfaces)
Do you process all triangles in a part together,
or just those who happens to be in a mesh ?
I assume you disregard triangles in subparts/primitives ?
What do you mean by "degenerated trangle" ?
/Lars
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Message has 1 Reply:
 | | Re: Smooth surfaces
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| (...) Another idea is to choose different angles depending on how long the edges are next to that angle. For longer edges, a smaller bend is more likely to be a real crease. I used to use this sort of heuristic in edge detection image processing (...) (23 years ago, 21-Sep-01, to lugnet.cad.ray)
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Message is in Reply To:
| | Smooth surfaces
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| Hi, I think the following is of interest in this newsgroup: L3P generates "meshes" of parts from Ldraw, that are not in LGEO and not covered by other special handling. Meshes consist of triangles and there are creases, if triangles from different (...) (23 years ago, 13-Sep-01, to lugnet.cad.ray)
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