[Gmsh] mesh problem

Sat Dec 19 11:43:44 CET 2009

Hi Stefano,

which CAD software do you use to create your geometry ?

I strongly suggest you to export your geometry in the STEP format instead of the IGES format

Concerning your 2D mesh, as you have seen by Checking Tools -> Options -> Mesh -> Visibility -> Surface Faces , some 
surfaces are partially superposed and cross each other. You can partially solve this problem by refining the mesh , 
setting the Tools -> Options -> Mesh -> General -> Element Size Factor to 0.1 or less ...

But I think that your geometry is still not clean enough, there are still some errors and warning messages during the 1D 
and 2D meshing

Regards,

Dave

--
David Colignon, Ph.D.
Collaborateur Logistique du F.R.S.-FNRS
CÉCI - Consortium des Équipements de Calcul Intensif
ACE - Applied & Computational Electromagnetics
Institut Montefiore B28
Université de Liège
4000 Liège - BELGIQUE
Tél: +32 (0)4 366 37 32
Fax: +32 (0)4 366 29 10
WWW:    http://hpc.montefiore.ulg.ac.be/
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On 18/12/09 23:57, stefano zinna wrote:
> Dear Dave.
>
> I cleaned the iges file
> (https://download.yousendit.com/Z01PcXlsaTFTSUNGa1E9PQ) and generate a
> surface mesh(https://download.yousendit.com/Z01PcXlnaFJ6RS9IRGc9PQ). The
> mesh has some problem because there are some intersected surfaces that
> you can see in the mesh.
> This is due to the geometry tolerance. What do you think? How can i
> solve this problem?
>
> thanks again for your kind reply.
>
> Stefano
>
>
>
> David Colignon wrote:
>> If you just open your step file with Gmsh, you can see that there are
>> some warnings and some errors:
>>
>> ...
>> ...
>> Info : removing degenerated edge 0
>> Info : removing degenerated edge 0
>> Info : - fixing wire gaps
>> Info : some 2D gaps fixed
>> Info : some 3D gaps fixed
>> Info : failed to fix some 2D gaps
>> Info : failed to fix some 3D gaps
>> Info : - fixing spot and strip faces
>> Warning : OCC STL triangulation failed
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Warning : OCC STL triangulation failed
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> Info : OCC Region 1 - New Shell
>> Info : OCC Region 1 with 2001 faces
>> Info : Read '/Users/colignon/Desktop/newfile.stp'
>>
>>
>> but they are perhaps not "blocking".
>> In Tools -> Options -> Geometry -> General , Gmsh has some *basic* and
>> *experimental* reparation features. You can increase the Tolerance, ...
>> But you should check and clean your geometry in your CAD software. For
>> example, with Tools -> Visibility, and by displaying the surfaces with
>> "ALT+s" you can see that for some reason Gmsh cannot display properly
>> surface 903
>>
>> If you use the command line to try to mesh your geometry in 2D, you
>> will get much more messages which could help you to find the problems
>> in your geometry (note that Gmsh crashes before the end)
>>
>> ace35:~/Desktop > gmsh newfile.stp -2
>>
>> Info : Running '/Applications/Gmsh.app/Contents/Resources/bin/gmsh
>> newfile.stp -2'
>> Info : Started on Fri Dec 18 10:32:01 2009
>> Info : Reading 'newfile.stp'
>> *** Error on Record 4039 (on 440531 -> 0 % in File) *** Ident #2022
>> Complex Type incorrect : SOLID_ANGLE_UNIT / SI_UNIT ...
>> *** Error on Record 27742 (on 440531 -> 6 % in File) *** Ident #9776
>> Complex Type incorrect : RATIONAL_B_SPLINE_SURFACE / BOUNDED_SURFACE ...
>> *** Error on Record 27744 (on 440531 -> 6 % in File) *** Ident #9776
>> Complex Type incorrect : REPRESENTATION_ITEM /
>> GEOMETRIC_REPRESENTATION_ITEM ...
>> *** Error on Record 37721 (on 440531 -> 8 % in File) *** Ident #12125
>> Complex Type incorrect : NAMED_UNIT / LENGTH_UNIT ...
>> *** Error on Record 340757 (on 440531 -> 77 % in File) *** Ident #171717
>> Complex Type incorrect : RATIONAL_B_SPLINE_CURVE / BOUNDED_CURVE ...
>> *** Error on Record 340759 (on 440531 -> 77 % in File) *** Ident #171717
>> Complex Type incorrect : REPRESENTATION_ITEM /
>> GEOMETRIC_REPRESENTATION_ITEM ...
>> *** Error on Record 340760 (on 440531 -> 77 % in File) *** Ident #171717
>> Complex Type incorrect : GEOMETRIC_REPRESENTATION_ITEM / CURVE ...
>> *** Error on Record 341398 (on 440531 -> 77 % in File) *** Ident #172039
>> Complex Type incorrect : RATIONAL_B_SPLINE_CURVE / BOUNDED_CURVE ...
>> *** Error on Record 341400 (on 440531 -> 77 % in File) *** Ident #172039
>> Complex Type incorrect : REPRESENTATION_ITEM /
>> GEOMETRIC_REPRESENTATION_ITEM ...
>> *** Error on Record 341401 (on 440531 -> 77 % in File) *** Ident #172039
>> Complex Type incorrect : GEOMETRIC_REPRESENTATION_ITEM / CURVE ...
>> *** Error on Record 348024 (on 440531 -> 79 % in File) *** Ident #174944
>> Complex Type incorrect : RATIONAL_B_SPLINE_CURVE / BOUNDED_CURVE ...
>> *** Error on Record 348026 (on 440531 -> 79 % in File) *** Ident #174944
>> Complex Type incorrect : REPRESENTATION_ITEM /
>> GEOMETRIC_REPRESENTATION_ITEM ...
>> *** Error on Record 348027 (on 440531 -> 79 % in File) *** Ident #174944
>> Complex Type incorrect : GEOMETRIC_REPRESENTATION_ITEM / CURVE ...
>> *** Error on Record 349696 (on 440531 -> 79 % in File) *** Ident #175652
>> Complex Type incorrect : RATIONAL_B_SPLINE_CURVE / BOUNDED_CURVE ...
>> *** Error on Record 349698 (on 440531 -> 79 % in File) *** Ident #175652
>> Complex Type incorrect : REPRESENTATION_ITEM /
>> GEOMETRIC_REPRESENTATION_ITEM ...
>> *** Error on Record 349699 (on 440531 -> 79 % in File) *** Ident #175652
>> Complex Type incorrect : GEOMETRIC_REPRESENTATION_ITEM / CURVE ...
>> Info : Healing geometry (tolerance=1e-06)
>> Info : - fixing small edges
>> Info : removing degenerated edge 0
>> ...
>> ...
>> Info : removing degenerated edge 0
>> Info : - fixing wire gaps
>> Info : some 2D gaps fixed
>> Info : some 3D gaps fixed
>> Info : failed to fix some 2D gaps
>> Info : failed to fix some 3D gaps
>> Info : - fixing spot and strip faces
>> Error : Something wrong in edge loop
>> Error : Something wrong in edge loop
>> ...
>> ...
>> Error : Something wrong in edge loop
>> Info : OCC Region 1 - New Shell
>> Info : OCC Region 1 with 2001 faces
>> Info : Read 'newfile.stp'
>> Info : Meshing 1D...
>> Info : Meshing curve 1 (BSpline)
>> ...
>> ...
>> ...
>> Info : Meshing curve 603 (BSpline)
>>
>> Info : Meshing curve 604 (Unknown)
>>
>> Info : Meshing curve 605 (BSpline)
>>
>> Info : Meshing curve 725 (Unknown)
>>
>> Info : Meshing curve 741 (Unknown)
>>
>> Info : Meshing curve 760 (Unknown)
>> Info : Meshing surface 100 (BSpline surface, MeshAdapt)
>> Info : Meshing surface 101 (Unknown, MeshAdapt)
>> Info : Meshing surface 102 (Unknown, MeshAdapt)
>> Info : Meshing surface 103 (Unknown, MeshAdapt)
>> Info : Meshing surface 104 (BSpline surface, MeshAdapt)
>> Warning : :-( There are 6 intersections in the 1D mesh (curves 501 448
>> 495 502 447 454)
>> Warning : 8-| Gmsh splits those edges and tries again
>> Warning : :-( There are 2 intersections in the 1D mesh (curves 447 454)
>> Warning : 8-| Gmsh splits those edges and tries again
>> Warning : :-) Gmsh was able to recover all edges after 2 iterations
>> Info : Meshing surface 105 (Plane, MeshAdapt)
>>
>> Info : Meshing surface 210 (BSpline surface, MeshAdapt)
>> Warning : :-( There are 3 intersections in the 1D mesh (curves 890 892
>> 894)
>> Warning : 8-| Gmsh splits those edges and tries again
>> Warning : :-( There are 3 intersections in the 1D mesh (curves 890 894
>> 892)
>> Warning : 8-| Gmsh splits those edges and tries again
>> Warning : :-( There are 3 intersections in the 1D mesh (curves 890 892
>> 894)
>> Warning : 8-| Gmsh splits those edges and tries again
>> Warning : :-( There are 2 intersections in the 1D mesh (curves 892 890)
>> Warning : 8-| Gmsh splits those edges and tries again
>> Warning : :-) Gmsh was able to recover all edges after 4 iterations
>> Info : Meshing surface 211 (BSpline surface, MeshAdapt)
>>
>> Info : Meshing surface 274 (Plane, MeshAdapt)
>> Warning : :-( There are 6 intersections in the 1D mesh (curves 1195
>> 1195 1196 1196 1181 1182)
>> Warning : 8-| Gmsh splits those edges and tries again
>> Info : Meshing surface 275 (BSpline surface, MeshAdapt)
>>
>> Info : Meshing surface 336 (BSpline surface, MeshAdapt)
>> Warning : :-( There are 3 intersections in the 1D mesh (curves 1428
>> 1429 1438)
>> Warning : 8-| Gmsh splits those edges and tries again
>> Warning : :-( There are 3 intersections in the 1D mesh (curves 1429
>> 1429 1437)
>> Warning : 8-| Gmsh splits those edges and tries again
>> Warning : :-) Gmsh was able to recover all edges after 2 iterations
>> Info : Meshing surface 337 (BSpline surface, MeshAdapt)
>>
>> Info : Meshing surface 348 (Plane, MeshAdapt)
>> Warning : :-( There are 5 intersections in the 1D mesh (curves 1213
>> 1216 1216 1479 1479)
>> Warning : 8-| Gmsh splits those edges and tries again
>> Info : Meshing surface 349 (BSpline surface, MeshAdapt)
>>
>>
>> Dave
>>
>>
>>
>>
>> On 18/12/09 09:52, stefano zinna wrote:
>>> Dear David.
>>>
>>> Thank you for the fast reply. I made a routine to avoid double lines so
>>> i think this isn't the problem.
>>> I have the original step file
>>> (https://download.yousendit.com/Z01PSkhYcVhuSlIzZUE9PQ). Can you explain
>>> which steps are better to generate the mesh?
>>>
>>> kind regards,
>>> Stefano
>>>
>>> David Colignon wrote:
>>>>
>>>> On 17/12/09 18:36, stefano zinna wrote:
>>>>> Dear Sirs.
>>>>>
>>>>> I converted a .stl file into .geo
>>>>> (https://download.yousendit.com/Z01NSU5OOW5samQzZUE9PQ) for gmsh.
>>>>
>>>> Hi Stefano,
>>>>
>>>> very nice geometry !
>>>>
>>>> Are you *sure* that each line shared by two triangles is only defined
>>>> once ? (it seems to be the case...)
>>>>
>>>> I'm
>>>>> able to generate the surface mesh but it is not able to recognize the
>>>>> volume. Is it a problem in the file or it depends on the complexity of
>>>>> the geometry?
>>>>
>>>>
>>>> When you try to create the volume with the GUI and you click on a
>>>> first surface, you can see that almost all the surfaces are then
>>>> selected and change color to red. But the GUI keep asking to select
>>>> volume boundary to fully close the volume. Due to the complexity of
>>>> the geometry, it is very difficult to detect with the eye by zooming
>>>> on every part of the geometry if some surfaces are missing, so I
>>>> cannot see there is a real problem in the geometry or if some surfaces
>>>> are left unselected...
>>>>
>>>> Converting your CAD file to the STL format and then converting it to
>>>> .geo is not the best solution. Do you have access to the original CAD
>>>> file ? Can you try to export it to the STEP format instead ?
>>>>
>>>> Regards,
>>>>
>>>> Dave
>>>>
>>>
>>
>