[Gmsh] Error when switching from Built-In to OpenCascade Factory

[Martin.Raedel at dlr.de]

Hello,

I want to add some information.

Yes, for the test case I could simply switch to "Plane Surface" and everything is working. But in reality, my models also consist on non-planar surfaces. I added another test as an attachment to this mail.

I found that if I increment the Line Loop and Surface numbers by 2 instead of 1, e.g. from the attached example:

Line Loop(1) = {10,2,11,3};
Surface(1) = {1};
Transfinite Surface(1) = {};
Recombine Surface(1) = 60.0;
Physical Surface(1) = {1};

Line Loop(3) = {12,4,13,5};
Surface(3) = {3};
Transfinite Surface(3) = {};
Recombine Surface(3) = 60.0;
Physical Surface(3) = {3};

no errors occur as well. This matches the error message. It seems that with the OpenCASCADE Factory, additional line loops are created internally. Changing this in my code would be possible but work I would rather avoid.

Can someone explain to me what where the different treatment of "Plane Surface" and "Surface" with respect to the line loops comes from? The documentation<http://gmsh.info/doc/texinfo/gmsh.html#Surfaces> says "Surface" is a "surface filling". What does that mean exactly?

Best regards
Martin

Von: gmsh [mailto:gmsh-bounces at ace20.montefiore.ulg.ac.be] Im Auftrag von Martin.Raedel at dlr.de
Gesendet: Sonntag, 8. Juli 2018 17:01
An: gmsh at onelab.info
Betreff: [Gmsh] Error when switching from Built-In to OpenCascade Factory

Hello,

I just recently tried to switch from the built-in Factory to OpenCascade to use Boolean operations.

However, all of my tests involving more than one surface crash after the switch with the same error:

OpenCascade wire or line loop with tag 2 already exists

The same error occurs for all other surfaces except the first.

I added a simple brick geometry example. In case I comment out "SetFactory("OpenCASCADE"); " everything works fine. If I use the line, the errors occur.

Can someone please point out what causes these errors and how I can fix them?

Best regards
Martin Rädel

------------------------
Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)
German Aerospace Center
Institute of Composite Structures and Adaptive Systems | Structural Mechanics | Lilienthalplatz 7 | 38108 Braunschweig | Germany

Dipl.-Ing. Martin Rädel
Telephone +49 (0)531 295-2048 | Telefax +49 (0)531 295-2232 | martin.raedel at dlr.de<mailto:martin.raedel at dlr.de>
www.DLR.de<http://www.dlr.de/>

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