[Gmsh] node positions on B-splines

[Rene Schneider]

Hi,

I'll try the SVN version tomorrow. I've had a look at the example in the 
bugreport you provided. It appears to be the same problem: The new 
vertices are placed too close to or too far from the edges that are 
extruded from the endpoints of the B-spline, suggesting that the 
distance evaluation along the (extruded) B-spline is wrong.

I guess that confirms that this is a bug.

Rene

On 19.02.13 17:49, Eiser, Sebastian wrote:
> I cannot open your file with my svn version...
> Error   : Line Loop 17 is wrong
> Error   : Line Loop 18 is wrong
> Error   : Line Loop 19 is wrong
> Error   : Line Loop 20 is wrong
>
> Anyways, have you tried using the 'Layers' command in your extrusion? It will produce prisms.
>
> Unfortunately, there is also a known problem with extruded layers when refining:
> https://geuz.org/trac/gmsh/ticket/184 (gmsh:gmsh)
>
>
>
> -----Original Message-----
> From: gmsh-bounces at ace20.montefiore.ulg.ac.be [mailto:gmsh-bounces at ace20.montefiore.ulg.ac.be] On Behalf Of Rene Schneider
> Sent: Thursday, February 14, 2013 2:49 PM
> To: gmsh at geuz.org
> Subject: [Gmsh] node positions on B-splines
>
> Hi
>
> First of all, thanks for providing this great software.
>
> I'm trying to mesh a 3D geometry defined by extruding B-spline segments, see attached example.
>
> I noticed that nodes accumulate close to the lines that originate from extruding the end-points of the B-splines, resulting in extremely thin surface triangles. Thus fairly bad tets are generated in the 3d mesh in these regions.
>
> Even worse: if the mesh is refined, the surface triangles are "sucked"
> into this region, degenerating to zero surface area. Correspondingly tets result, with zero volume.
>
> I presume this problem could result from an error in distance measurement on the surface.
>
> If I use splines instead of B-splines, the problem is gone.
>
> Any help is appreciated, I really need those B-splines.
>
> I'm using
> $ gmsh --version
> 2.6.1
> under Linux.
>
>
> Rene
>


-- 
----------------------------------------------------

       Dr. Rene Schneider

       TU Chemnitz, Fakultaet fuer Mathematik,
       09107 Chemnitz, Germany

       Besucheradresse / Visitor address:
       Reichenhainer Str. 41 / Raum 625
       09126 Chemnitz, Germany

       Tel.: +49-371-531-33953
       Fax:  +49-371-531-8-33953
       rene.schneider at mathematik.tu-chemnitz.de

       http://www.tu-chemnitz.de/~rens

----------------------------------------------------