[Gmsh] Error : Self intersecting surface mesh, computing intersections (this could take a while)
Steffen Becker
steffenbecker87 at yahoo.de
Tue Mar 18 21:41:34 CET 2014
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:steffenbecker87 at yahoo.de]
> *Gesendet:* Montag, 17. März 2014 22:39
> *An:* Zenker, Dr. Matthias
> *Cc:* Roman Fratczak; gmsh at 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:steffenbecker87 at yahoo.de]
> *Gesendet:* Montag, 17. März 2014 11:20
> *An:* Zenker, Dr. Matthias
> *Cc:* Roman Fratczak; gmsh at geuz.org <mailto:gmsh at 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:steffenbecker87 at yahoo.de]
> *Gesendet:* Montag, 17. März 2014 10:55
> *An:* Zenker, Dr. Matthias
> *Cc:* Roman Fratczak; gmsh at geuz.org <mailto:gmsh at 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:steffenbecker87 at yahoo.de]
> *Gesendet:* Freitag, 14. März 2014 21:09
> *An:* Zenker, Dr. Matthias
> *Cc:* Roman Fratczak; gmsh at geuz.org <mailto:gmsh at 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:steffenbecker87 at yahoo.de]
> *Gesendet:* Freitag, 14. März 2014 12:33
> *An:* Zenker, Dr. Matthias
> *Cc:* Roman Fratczak; gmsh at geuz.org <mailto:gmsh at 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:steffenbecker87 at yahoo.de]
> *Gesendet:* Mittwoch, 12. März 2014 20:00
> *An:* Roman Fratczak
> *Cc:* Zenker, Dr. Matthias; gmsh at geuz.org
> <mailto:gmsh at 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:fratczakroman at o2.pl]
> *Gesendet:*Mittwoch, 12.
> März 2014 09:51
> *An:* Steffen Becker
> *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)
>
> 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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> _____________________________________________________________________
> ERBE Elektromedizin GmbH
> Firmensitz: 72072 Tuebingen
> Geschaeftsfuehrer:
> Christian O. Erbe, Reiner
> Thede
> Registergericht: Stuttgart
> HRB 380137
>
>
>
> _____________________________________________________________________
> ERBE Elektromedizin GmbH
> Firmensitz: 72072 Tuebingen
> Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> Registergericht: Stuttgart HRB 380137
>
>
>
> _____________________________________________________________________
> ERBE Elektromedizin GmbH
> Firmensitz: 72072 Tuebingen
> Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> Registergericht: Stuttgart HRB 380137
>
>
>
> _____________________________________________________________________
> ERBE Elektromedizin GmbH
> Firmensitz: 72072 Tuebingen
> Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> Registergericht: Stuttgart HRB 380137
>
>
>
> _____________________________________________________________________
> ERBE Elektromedizin GmbH
> Firmensitz: 72072 Tuebingen
> Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> Registergericht: Stuttgart HRB 380137
>
>
>
> _____________________________________________________________________
> ERBE Elektromedizin GmbH
> Firmensitz: 72072 Tuebingen
> Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> Registergericht: Stuttgart HRB 380137
>
>
>
> _____________________________________________________________________
> ERBE Elektromedizin GmbH
> Firmensitz: 72072 Tuebingen
> Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> Registergericht: Stuttgart HRB 380137
>
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