[Gmsh] Error : Self intersecting surface mesh, computing intersections (this could take a while)
Steffen Becker
steffenbecker87 at yahoo.de
Wed Mar 12 19:59:35 CET 2014
Hi,
I'm so sorry for all time you spent with my problem, but now I see: We
talk at cross. It's my fault, I didn't explained correctly what I need.
I want to receive a *filled* volume mesh.
I created 2 files (steffen.stl and steffen2.stl) with my python script.
With steffen.stl I successfully could create such a filled volume mesh
as seen in steffen.msh.
When I try exactly the same with steffen2.stl then I get the error
message in the subject (and the surface mesh doesn't get filled).
So that's why the .iges file you sent me isn't what I need.
Sorry for all this confusion,
Steffen
Am 12.03.2014 18:53, schrieb Roman Fratczak:
> Steffen,
>
> I did a volume based on your surface mesh - see attached IGES
> (compressed with 7-zip).
> After reading it into GMSH, you can create the 1D, then 2D and finally
> 3D mesh with no errors.
>
> You can do the same using GMSH volume definition (as already wrote)->
> it will work, as the fundamental faces are plane triangles.
>
> Regards
> Roman
>
>
> W dniu 12.03.2014 18:27, Steffen Becker pisze:
>> Wrong .geo file, sorry!
>>
>> Am 12.03.2014 18:21, schrieb Steffen Becker:
>>> Thank you so far,
>>>
>>> I create both files: .msh and .geo, but I still get the same error.
>>> What's my mistake?
>>>
>>> Steffen
>>>
>>> Am 12.03.2014 11:48, schrieb Roman Fratczak:
>>>> Hi,
>>>>
>>>> FYI - you can remove double vertices/edges (or repair) in mesh in
>>>> FreeCad (for exampe).
>>>>
>>>> regards
>>>> Roman
>>>>
>>>>
>>>>
>>>> W dniu 12.03.2014 10:17, Steffen Becker pisze:
>>>>> Hi Matthias & Roman,
>>>>>
>>>>> I create a nodes- and elements-list like this:
>>>>> # nodes:
>>>>> N1 0,0,0
>>>>> N2 0,1,0
>>>>> N3 1,0,0
>>>>> N4 0,0,1
>>>>> # elements, which describe triangles:
>>>>> E1 1,2,3
>>>>> E2 2,3,4
>>>>>
>>>>> So I do have double edges (here: between node 2+3). Didn't now
>>>>> that this is a problem for gmsh, sorry.
>>>>>
>>>>> I will try Romans solution asap and give you a feedback.
>>>>> Thank you both!
>>>>>
>>>>> Steffen
>>>>>
>>>>>
>>>>> Am 12.03.2014 09:59, schrieb Zenker, Dr. Matthias:
>>>>>>
>>>>>> Hi Steffen,
>>>>>>
>>>>>> I am not totally sure from what you wrote that there are really
>>>>>> no duplicated nodes. In gmsh, you need to define the surfaces in
>>>>>> a way that neighbouring surfaces/facets with a common border use
>>>>>> the _/same/_ nodes to define the border. I could not see from
>>>>>> your file if there are duplicated nodes, and would propose that
>>>>>> you make sure that there are really no such duplications.
>>>>>>
>>>>>> If the meshing still fails, then this is a question for the real
>>>>>> gurus (Christophe?).
>>>>>>
>>>>>> HTH,
>>>>>>
>>>>>> Matthias
>>>>>>
>>>>>> *Von:*Roman Fratczak [mailto:fratczakroman at o2.pl]
>>>>>> *Gesendet:*Mittwoch, 12. März 2014 09:51
>>>>>> *An:* Steffen Becker
>>>>>> *Cc:* gmsh at geuz.org
>>>>>> *Betreff:* Re: [Gmsh] Error : Self intersecting surface mesh,
>>>>>> computing intersections (this could take a while)
>>>>>>
>>>>>> Hi Steffen,
>>>>>>
>>>>>> No it is more clear. If you are working with cloud of point, then
>>>>>> you may use Meshlab for surface regeneration. There are many
>>>>>> software that are able to handle in a resonable way the cloud of
>>>>>> points (like rhino3D + resurf, other). But these are rather
>>>>>> commercial.
>>>>>>
>>>>>> From the other side - try to do the simplest thing:
>>>>>>
>>>>>> Adjust your python script for surface creation in order to save
>>>>>> not as PLY but as GMSH "geo" file using points and lines
>>>>>>
>>>>>> Point(1)={0,0,0} ;
>>>>>> Point(2)={0,1,0} ;
>>>>>> ...
>>>>>>
>>>>>> Line(1) = {1,2};
>>>>>> ..
>>>>>> and.. Line Loop & Surface -> Volume ..
>>>>>>
>>>>>> Then you will get a volume defined by geometric entities. In this
>>>>>> case is shoul be easier to create a better mesh on surface and
>>>>>> then on whole volume.
>>>>>>
>>>>>> Regards
>>>>>> Roman
>>>>>>
>>>>>>
>>>>>>
>>>>>> W dniu 11.03.2014 17:59, Steffen Becker pisze:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> @ Roman:
>>>>>> some more details:
>>>>>> I have a point cloud given and generate the surface mesh by
>>>>>> myself (with python). I don't know a good algorithm to create
>>>>>> a volume mesh out of this surface mesh - that's why I use
>>>>>> gmsh for this task.
>>>>>> I also checked my surface mesh for double vertexes but I
>>>>>> didn't find any. What do you mean with "double egdes"? Isn't
>>>>>> there always a "double edge", because two neighbour facets
>>>>>> always have one same edge?!
>>>>>>
>>>>>> I will send you a .step or .iges file as soon as I figured
>>>>>> out how to handle the "No OpenCASCADE model found" error.
>>>>>>
>>>>>> I'm appending the other mailing history (with Matthias) to
>>>>>> this mail - sorry for that "double mailing", I just forgot
>>>>>> one time to "reply to all" -.-
>>>>>> Anyone else has an idea why the meshing fails?
>>>>>>
>>>>>> Regards and thank you a lot,
>>>>>> Steffen
>>>>>>
>>>>>>
>>>>>>
>>>>>> Hi Steffen,
>>>>>>
>>>>>>
>>>>>>
>>>>>> I don't see either why the meshing fails, sorry.
>>>>>>
>>>>>>
>>>>>>
>>>>>> Matthias
>>>>>>
>>>>>>
>>>>>>
>>>>>> -----Ursprüngliche Nachricht-----
>>>>>>
>>>>>> Von: Steffen Becker [mailto:steffenbecker87 at yahoo.de]
>>>>>>
>>>>>> Gesendet: Dienstag, 11. März 2014 14:42
>>>>>>
>>>>>> An: Zenker, Dr. Matthias
>>>>>>
>>>>>> Cc:gmsh at geuz.org <mailto:gmsh at geuz.org>
>>>>>>
>>>>>> Betreff: Re: [Gmsh] Error : Self intersecting surface mesh, computing
>>>>>>
>>>>>> intersections (this could take a while)
>>>>>>
>>>>>>
>>>>>>
>>>>>> Oh I'm really sorry, here is the file.
>>>>>>
>>>>>> In addition I sent you also the intersect.pos. I don't understand why exactly
>>>>>>
>>>>>> these surfaces are problematic and the "neighbour surfaces"
>>>>>>
>>>>>> aren't - although they have the same geometry =/
>>>>>>
>>>>>>
>>>>>>
>>>>>> Am 11.03.2014 12:07, schrieb Zenker, Dr. Matthias:
>>>>>>
>>>>>> Hi Steffen,
>>>>>>
>>>>>>
>>>>>>
>>>>>> if you don't provide the myfile.ply2, we cannot see your geometry...
>>>>>>
>>>>>> You can visualize intersect.pos by merging it to your geometry.
>>>>>>
>>>>>>
>>>>>>
>>>>>> HTH,
>>>>>>
>>>>>>
>>>>>>
>>>>>> Matthias
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Am 11.03.2014 14:33, schrieb Roman Fratczak:
>>>>>>
>>>>>> Hello,
>>>>>>
>>>>>> It is possible, that you will get your geometry in other
>>>>>> format?
>>>>>> In your "ply" there is already a surface mesh given. Try
>>>>>> maybe use STEP, IGES,... as input- then it is easer to
>>>>>> recalculate the surface mesh.
>>>>>>
>>>>>> In case of need of usage of "a dead mesh" - maybe try
>>>>>> first to remesh it (i.e. in blender with modification
>>>>>> Remesh) and/or clean it (removing double vertexes and edges).
>>>>>>
>>>>>> regards
>>>>>> Roman
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> W dniu 11.03.2014 12:13, Steffen Becker pisze:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> in the appendix you find my model.
>>>>>> Thanks for help!!
>>>>>>
>>>>>> Regards,
>>>>>> Steffen
>>>>>>
>>>>>> Am 11.03.2014 11:47, schrieb Roman Fratczak:
>>>>>>
>>>>>> Hello Steffen,
>>>>>>
>>>>>> Yes. You can try to the first Optimize quality of
>>>>>> tetra, or all of them (just try).
>>>>>>
>>>>>> I don't know how your model looks like. If the
>>>>>> elements on the surface are too big, then the
>>>>>> solid elements (probably tetragonal) may be with
>>>>>> intersecting edges or faces. Therefore the
>>>>>> reducing size of element may help (especially on
>>>>>> the surfaces).
>>>>>>
>>>>>> Or- just share your model (ply) -in order to be
>>>>>> more precise.
>>>>>>
>>>>>> regards
>>>>>> Roman
>>>>>>
>>>>>>
>>>>>>
>>>>>> W dniu 10.03.2014 18:06, Steffen Becker pisze:
>>>>>>
>>>>>> Hi Roman,
>>>>>> when you say "enable option: optimize", you
>>>>>> mean" Tools -> Options -> Mesh -> Advanced ->
>>>>>> Optimize quality of tetrahedra, Optimize
>>>>>> quality of tetrahedra with Netgen, Optimize
>>>>>> high order meshes (experimental)" ?
>>>>>> And why is reducing element size important?
>>>>>> In my case it is important that the object
>>>>>> has such "90 degree corners".
>>>>>>
>>>>>> Regards,
>>>>>> Steffen
>>>>>>
>>>>>> Am 10.03.2014 16:55, schrieb Roman Fratczak:
>>>>>>
>>>>>> Hi Steffen,
>>>>>>
>>>>>> If your volume is OK (is really a closed
>>>>>> one) - try to:
>>>>>>
>>>>>> 1. Reduce element size (especially in a
>>>>>> curved shapes)
>>>>>> 2. Enable option "Optimize" - in mesh
>>>>>> options
>>>>>>
>>>>>> Regards
>>>>>> Roman
>>>>>>
>>>>>>
>>>>>>
>>>>>> W dniu 10.03.2014 16:41, Steffen Becker
>>>>>> pisze:
>>>>>>
>>>>>> Hello everyone,
>>>>>>
>>>>>> I'm a gmsh beginner and I want to
>>>>>> create a 3D volume mesh out of a
>>>>>> given surface-mesh but I got the
>>>>>> error message as seen in the subject.
>>>>>> You find my .geo file in the appendix.
>>>>>> Can anyone tell me what I have to do
>>>>>> to create a 3D mesh? I even can't
>>>>>> figure out where the intersection are
>>>>>> located (don't know how to read the
>>>>>> intersect.pos).
>>>>>> Sorry for my poor english.
>>>>>>
>>>>>> Regards,
>>>>>> Steffen
>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>>
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>>>>>>
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>>>>>>
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>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
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>>>>>>
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>>>>>>
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>>>>>>
>>>>>>
>>>>>>
>>>>>>
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>>>>>
>>>>
>>>
>>
>
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