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:[email protected]]
*Gesendet:*Mittwoch, 12. März 2014 09:51
*An:* Steffen Becker
*Cc:* [email protected]
*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:[email protected]]
Gesendet: Dienstag, 11. März 2014 14:42
An: Zenker, Dr. Matthias
Cc:[email protected] <mailto:[email protected]>
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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