[Gmsh] bad orientation

Fri May 15 10:17:35 CEST 2020

Dear all,

I am not familiar with FreeFEM++...
The mesh generation happens without any issue.

If the problem is the normal orientation, maybe you could invert the normal at the end of the geo file, for whatever surface you want.
e.g. with the file you sent, for having outward normals in the mesh you should add
Reverse Surface{1,13,15,14};

Alternative to changing the loops.
Best regards,
Ruth

—
Prof. Ruth V. Sabariego
KU Leuven, Dept. Electrical Engineering ESAT/Electa, EnergyVille
http://www.esat.kuleuven.be/electa
http://www.energyville.be

On 15 May 2020, at 08:55, Jose Juan Alonso del Rosario <josejuan.alonso at gm.uca.es<mailto:josejuan.alonso at gm.uca.es>> wrote:

Dear Ugis and colleages of GMSH,

Thank you for your suggestions. I have changed the loop orientation of the upper and lower faces of the pentagon and the whole volumen was meshed (no hole at the end). In addition the same error still happens.

"read mesh ok 0Mesh3, num Tetra:= 24011, num Vertice:= 5665 num boundary Triangles:= 6078
Mesh3::meshS, num Triangles:= 6078, num Vertice:= 3039 num boundary Edges:= 354
read mesh ok 0Mesh3, num Tetra:= 24011, num Vertice:= 5665 num boundary Triangles:= 6078
Mesh3::meshS, num Triangles:= 6078, num Vertice:= 3039 num boundary Edges:= 354
 Bad orientation: The adj border element  defined by [  3 210 ]  is oriented in the same direction in element 3519 and in the element 367 ****** bug in mesh construction? orientation parameter?
S, num Triangles:= 6078, num Vertice:= 3039 num boundary Edges:= 354
 Bad orientation: The adj border element  defined by [  3 210 ]  is oriented in the same direction in element 3519 and in the element 367 ****** bug in mesh construction? orientation parameter? "

This is after several Optimize3D and Optimize 3d with NetGen and reading it with freefem++

I include the .geo code. It is a thick slice with a pentagonal hole. The gmsh is now 4.5.6 and the meshing options are MeshAdapt and Frontal. I have played with the signs of plane surfaces 14 and 15.

Thanks in advance!!!

Jose

El jue., 14 may. 2020 a las 13:54, Ugis Lacis (<ugis.lacis at gmail.com<mailto:ugis.lacis at gmail.com>>) escribió:
Dear Jose,

I think I have had similar error, when importing GMSH mesh into FreeFEM++, few years ago (although it seems that the error message might have changed). It turned out that the direction of loop definition in GMSH was the issue for me. See below my exchange with FreeFEM++ mailing list.

Maybe it can be helpful for you.

Best regards,
Ugis Lacis
Researcher
KTH Mechanics

------------------------------------------------------------------------------------------------------------------------------------------------------------------
-------- Forwarded Message --------
Subject:        Re: [Freefempp] Issue with loading mesh from GMSH.
Date:   Fri, 3 Aug 2018 09:41:29 +0200
From:   Uģis Lācis <ugis.lacis at gmail.com><mailto:ugis.lacis at gmail.com>
To:     FreeFem mailing list <freefempp at ljll.math.upmc.fr><mailto:freefempp at ljll.math.upmc.fr>

Hi everyone,

I managed to solve the issue myself. It turned out that the direction of GMSH loop was surviving till FreeFEM++ and while GMSH did not complain about anything, FreeFEM++ couldn't use the mesh. mesh2 could be fixed by changing signs in all lines within the line loop, i.e.,
change
Line Loop(5) = {18, 19, 20, 12, 7, 8};
to
Line Loop(5) = {-18, -19, -20, -12, -7, -8};

Maybe this helps to someone at some point.

Best,
Ugis

On 02/08/18 15:30, Uģis Lācis wrote:
Dear FreeFEM++ users and developers,

I have run into an issue which I am unable to solve by myself. I have been using FreeFEM++ together with GMSH without any problems for quite some time. Now, however, trying to load a 2D mesh generated by GMSH, gives me following error:

Assertion fail : (area>0)
    line :281, in file ./include/fem.hpp

I attach the corresponding geo and msh files of two meshes (mesh1 - working fine, mesh2 - does not load), as well as edp file for reading and plotting the mesh.

I have carefully checked that physical tags are applied correctly, I have tried exporting both in MSH and MESH (medit) formats, using GMSH versions 3.06 and 2.16.0, as well as using FreeFEM++ versions 3.560000 and 3.610002, all try has led me to the same behaviour. I have identified that the issue comes from the surface mesh, if I export only line mesh (comment out "Physical Surface(11) = {3,4};" from mesh2.geo and run "gmsh -2 mesh2.geo"), then it loads fine. But checking the mesh within GMSH, everything seems to be perfectly fine...

Do you have any suggestions on how to solve this issue?

Best regards,
Ugis Lacis
Researcher
KTH Mechanics
------------------------------------------------------------------------------------------------------------------------------------------------------------------

On 14/05/2020 12:03, Jose Juan Alonso del Rosario wrote:
Dear colleages

I am trying to build the mesh for a slice with a pentagonal hole.
GMSH runs properly with good quality tets but when trying to read it from freefem++ the error is:

" Bad orientation: The adj border element  defined by [  16 246 ]  is oriented in the same direction in element 3922 and in the element 446 ****** bug in mesh construction? orientation parameter?
  current line = 12 mpirank 1 / 2
"
Can you give any advice on this?

Thanks in advance

Jose

--
Prof. Dr. Jose Juan Alonso del Rosario
Applied Physics Dept.,
Naval and Oceanic Engineering.
University of Cadiz.
Avda Rep Saharaui s/n. Puerto Real, 11510, Cadiz, Spain
Tlf: +34 956 016054
Fax: +34 956016079
Secretary: +34 956016078

"All I wanna say is that they don't really care about us", Michael Jackson

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--
Prof. Dr. Jose Juan Alonso del Rosario
Applied Physics Dept.,
Naval and Oceanic Engineering.
University of Cadiz.
Avda Rep Saharaui s/n. Puerto Real, 11510, Cadiz, Spain
Tlf: +34 956 016054
Fax: +34 956016079
Secretary: +34 956016078

"All I wanna say is that they don't really care about us", Michael Jackson
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