Hi Steffen,
no, I can't, as I am not a gmsh delopper and have not looked deeper into meshing algorithms. This question would be best answered by Christophe Geuzaine or Jean-Francois Remacle. On the gmsh homepage, there is a paper on gmsh where you may find more information. Also AFAIK there are several meshing algorithms implemented in gmsh.
Matthias
Von: Steffen Becker [mailto:***@yahoo.de]
Gesendet: Donnerstag, 20. März 2014 21:42
An: Zenker, Dr. Matthias
Cc: Roman Fratczak; ***@geuz.org
Betreff: Re: [Gmsh] Error : Self intersecting surface mesh, computing intersections (this could take a while)
Thank you a lot!
I couldn't yet find out why/where I create those ill-defined triangles, but that's not you problem ;-P
I have one last question:
Can you tell me in a short, easy way the algorithm how Gmsh creates new nodes inside the given surface-mesh?
Regards,
Steffen
Am 19.03.2014 09:15, schrieb Zenker, Dr. Matthias:
Hi Steffen,
the difference between 0 and 0.0000000001 might be a rounding error.
Now if you have holes in your surface if you just delete all ill-defined triangles, I don't know. It depends on how you made your triangulation. IMO it would be better to make sure that such triangles are not even be created.
Matthias
Von: Steffen Becker [mailto:***@yahoo.de]
Gesendet: Dienstag, 18. März 2014 21:47
An: Zenker, Dr. Matthias
Cc: Roman Fratczak; ***@geuz.org<mailto:***@geuz.org>
Betreff: Re: [Gmsh] Error : Self intersecting surface mesh, computing intersections (this could take a while)
What I just think about:
I just deleted all the lines in my elements-list where area is <= 0.000000001. Doesn't that mean that I have small holes in my surface mesh now? How is Gmsh able to work with this? I just don't understand why this makes a difference compared to just check if area is = 0
Steffen
Am 18.03.2014 21:41, schrieb Steffen Becker:
Hi,
puh, that's weird:
First I checked my triangles if their area is > 0 (to get the ones which are aligned). This didn't helped as I said in my last mail. Now I (just for fun) checked if the area > 0.000000001 and now it works - but I don't know why this is such a difference?!
Anyway, thanks for your help!
Steffen
Am 18.03.2014 10:57, schrieb Zenker, Dr. Matthias:
Hi Steffen,
there are still ill-defined triangles, e.g. 2319, 2320, 2321. You can find that out by yourself by inspecting your mesh with gmsh in the way I described in my last mail.
Remark: checking "surface faces" can help to examine the surface.
HTH,
Matthias
Von: Steffen Becker [mailto:***@yahoo.de]
Gesendet: Montag, 17. März 2014 22:39
An: Zenker, Dr. Matthias
Cc: Roman Fratczak; ***@geuz.org<mailto:***@geuz.org>
Betreff: Re: [Gmsh] Error : Self intersecting surface mesh, computing intersections (this could take a while)
Hi Matthias,
thank you for your help!
I think I successfully deleted all the triangles with zero surface. Unfortunately the same error still appears (but at least with much less intersections). You find my new .msh file in the appendix. Do you have more ideas?
Regards,
Steffen
Am 17.03.2014 11:37, schrieb Zenker, Dr. Matthias:
Hi Steffen,
I think you have ill-defined triangles in your mesh. For example, there is a triangle 15328 which contains the nodes 7358, 7359, and 7360. But these nodes are aligned, so the triangle has zero surface. I would suspect this kind of problem to be the cause for the failure. I discovered that by examining your mesh after merging the intersect.pos, and by displaying node labels and surface labels in gmsh. I saw that this triangle was not visible, just its label, and searched for "15328" in your msh file to see what nodes it contains.
You should make sure that this kind of thing cannot happen when you define the surface mesh.
HTH,
Matthias
Von: Steffen Becker [mailto:***@yahoo.de]
Gesendet: Montag, 17. März 2014 11:20
An: Zenker, Dr. Matthias
Cc: Roman Fratczak; ***@geuz.org<mailto:***@geuz.org>
Betreff: Re: [Gmsh] Error : Self intersecting surface mesh, computing intersections (this could take a while)
Here it is.
Am 17.03.2014 11:14, schrieb Zenker, Dr. Matthias:
Hi Steffen,
I found out: Outlook is wrong.
I just discovered a small info saying that Outlook thinks that my_file.msh is insecure and that it has deleted the attachment (Grrrr). So the fault was on my side, sorry. Could you try to send it again with a changed extension, e.g. rename it to my_file.msh.txt?
Matthias
Von: Steffen Becker [mailto:***@yahoo.de]
Gesendet: Montag, 17. März 2014 10:55
An: Zenker, Dr. Matthias
Cc: Roman Fratczak; ***@geuz.org<mailto:***@geuz.org>
Betreff: Re: [Gmsh] Error : Self intersecting surface mesh, computing intersections (this could take a while)
Hi Matthias,
I don't know what's wrong here.
When I check my mails, there is a .msh file in the mail from 12.03.2014 18:21 and also one in the mail from 14.03.2014 12:33.
Finally, I sent you again a .msh file in this mail. Do you receive it?
Steffen
Am 17.03.2014 09:52, schrieb Zenker, Dr. Matthias:
Hi Steffen,
in the mail you mention there is only a geo file...
Matthias
Von: Steffen Becker [mailto:***@yahoo.de]
Gesendet: Freitag, 14. März 2014 21:09
An: Zenker, Dr. Matthias
Cc: Roman Fratczak; ***@geuz.org<mailto:***@geuz.org>
Betreff: Re: [Gmsh] Error : Self intersecting surface mesh, computing intersections (this could take a while)
Hi Matthias,
hm, I sent it on 12.03.2014 18:21, don't know what went wrong.
As you see, I created a ASCII .msh file as explained in the documentation, so I hope it's correct.
What can I do now?
Steffen
Am 14.03.2014 13:05, schrieb Zenker, Dr. Matthias:
Hi Steffen,
there was no msh file in any of your mails.
Depending on what is in the msh file, your steps seem correct to me.
Matthias
Von: Steffen Becker [mailto:***@yahoo.de]
Gesendet: Freitag, 14. März 2014 12:33
An: Zenker, Dr. Matthias
Cc: Roman Fratczak; ***@geuz.org<mailto:***@geuz.org>
Betreff: Re: [Gmsh] Error : Self intersecting surface mesh, computing intersections (this could take a while)
Hi Matthias,
I think you are talking about your mail from 12.03.2014 09:59 ?
In one of my last mails I already sent you a selfcreated .msh file - but the 3D mesh still failes. The intersect.pos shows me some
intersections, but when I check my nodes for duplicates I can't find any.
Hope my steps are correct:
- create "my_file.msh" with my python script and check it for nodes duplications -> none found
- open "my_file.geo" in Gmsh
- do "Modules" -> "Mesh" -> "3D"
- receive error message
- merge "intersect.pos" and see some intersections but I don't know why because the are no duplicated nodes
Steffen
Am 14.03.2014 09:50, schrieb Zenker, Dr. Matthias:
Hi Steffen,
you should be able to generate a filled volume mesh if you follow my suggestion from the other mail:
Write the 2D mesh in gmsh format (e.g. as outerface.msh, gmsh documentation for more info on the msh format) and merge that one instead of the myfile.ply2 file, leaving the other command lines in your .geo file as they are. If you then do a 3D mesh, gmsh will take the 2D mesh as defined in your file. You can then refine the mesh if you wish.
HTH,
Matthias
Von: Steffen Becker [mailto:***@yahoo.de]
Gesendet: Mittwoch, 12. März 2014 20:00
An: Roman Fratczak
Cc: Zenker, Dr. Matthias; ***@geuz.org<mailto:***@geuz.org>
Betreff: Re: [Gmsh] Error : Self intersecting surface mesh, computing intersections (this could take a while)
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:***@o2.pl]
Gesendet: Mittwoch, 12. März 2014 09:51
An: Steffen Becker
Cc: ***@geuz.org<mailto:***@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.