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<p>Dear Christophe,</p>
<p wrap=""><i>I would recommend using the default one. <br>
</i></p>
<p wrap=""><i>(Is the quality of the STL meshes sufficient, or do
you need to remesh them?)</i><br>
</p>
<p wrap="">We have several steps of cleaning, smoothing and and
re-sampling surfaces before volume meshing in GMSH. We actually
want to do "curvature-weighed re-sampling". That is, we want to
re-sample our surfaces but keep the node density higher where the
mesh is more curved. Do you know of any algorithm that can do
that?<br>
</p>
<p wrap=""><i>Recent Gmsh versions optimize automatically. We will
introduce some fine-tuning in the future to change the
speed/quality tradeoff ; currently a good compromise is
hardcoded. <br>
</i></p>
<p wrap="">Looking forward to it! When we create our meshes, we
still notice a few bad-shaped elements. Is it because of the
surfaces? How do the surfaces constrain the volume meshing and
optimization?<br>
</p>
<p wrap=""><i>The official Linux binaries are compiled on the
"old-stable" Debian, in order to support even quite old Linux
distributions. Can you share the error you get on CentOS 6 ? <br>
</i></p>
<p wrap="">I get</p>
<p><tt>gmsh-4.0.1-Linux64/bin/gmsh: /usr/lib64/libstdc++.so.6:
version `GLIBCXX_3.4.14' not found (required by
gmsh-4.0.1-Linux64/bin/gmsh)</tt><tt><br>
</tt><tt> gmsh-4.0.1-Linux64/bin/gmsh: /usr/lib64/libstdc++.so.6:
version `CXXABI_1.3.5' not found (required by
gmsh-4.0.1-Linux64/bin/gmsh)</tt><tt><br>
</tt><tt> gmsh-4.0.1-Linux64/bin/gmsh: /usr/lib64/libstdc++.so.6:
version `GLIBCXX_3.4.15' not found (required by
gmsh-4.0.1-Linux64/bin/gmsh)</tt><br>
</p>
<p wrap="">CentOS 6 comes with an old glibc version, and updating it
is not trivial. Compiling gmsh on a CentOS 6 VM should solve this
issue</p>
<p wrap=""><i>Yes, that's indeed in our plans for a future revision
of the MSH4 format, together with even better handling of very
large meshes/datasets.</i></p>
<p wrap="">Nice!</p>
<p wrap="">By the way, I was implementing an I/O function for
version 4 binaries and I believe I found a mistake in the
documentation:</p>
<p class="example">"numNodes" in the blocks of both $Nodes and
$Elements seems to be an int, unsigned long. I also found that I
need to skip 4 bytes after each block header.</p>
<p class="example"><br>
</p>
<p class="example">Best Regards,</p>
<p class="example">Guilherme<br>
</p>
<p wrap=""><br>
</p>
<div class="moz-cite-prefix">On 09/12/2018 10:32 PM, Christophe
Geuzaine wrote:<br>
</div>
<blockquote type="cite"
cite="mid:DFA3E7E0-68B6-4D16-A4F5-A624C46DB964@uliege.be">
<pre wrap="">
</pre>
<blockquote type="cite">
<pre wrap="">On 12 Sep 2018, at 14:31, Guilherme Saturnino <a class="moz-txt-link-rfc2396E" href="mailto:guilhermebs@drcmr.dk"><guilhermebs@drcmr.dk></a> wrote:
Dear Gmsh developers,
I'm working on a package called SimNIBS (<a class="moz-txt-link-freetext" href="http://simnibs.org/">http://simnibs.org/</a>) that does FEM simulations in human head models. We use gmsh to create tetrahedral meshes from stl surfaces of brain and other tissues. Is there any particular meshing algorithm you would suggest for this application?
</pre>
</blockquote>
<pre wrap="">
I would recommend using the default one.
(Is the quality of the STL meshes sufficient, or do you need to remesh them?)
</pre>
<blockquote type="cite">
<pre wrap="">What about optimization algorithms? We prefer robustness and quality over speed.
</pre>
</blockquote>
<pre wrap="">
Recent Gmsh versions optimize automatically. We will introduce some fine-tuning in the future to change the speed/quality tradeoff ; currently a good compromise is hardcoded.
</pre>
<blockquote type="cite">
<pre wrap="">
I would also like to suggest 2 improvements for future Gmsh versions:
1. Is it possible to provide Gmsh 4 binaries that are compatible with CentOS 6? It is an old but still widely used Linux distribution. This has been holding us back in adopting Gmsh 4.
</pre>
</blockquote>
<pre wrap="">
The official Linux binaries are compiled on the "old-stable" Debian, in order to support even quite old Linux distributions. Can you share the error you get on CentOS 6 ?
</pre>
<blockquote type="cite">
<pre wrap="">
2. Would it be possible in future releases to have more flexible data types in $NodeData and $ElementNodeData? I think it would be very useful to store single-precision floats (to save space) or integers (to have additional labels for elements and nodes) .
</pre>
</blockquote>
<pre wrap="">
Yes, that's indeed in our plans for a future revision of the MSH4 format, together with even better handling of very large meshes/datasets.
Thanks for the feedback,
Christophe
</pre>
<blockquote type="cite">
<pre wrap="">
Thanks a lot for putting so much time and effort into making this great piece of software.
Best Regards,
Guilherme Saturnino
_______________________________________________
gmsh mailing list
<a class="moz-txt-link-abbreviated" href="mailto:gmsh@onelab.info">gmsh@onelab.info</a>
<a class="moz-txt-link-freetext" href="http://onelab.info/mailman/listinfo/gmsh">http://onelab.info/mailman/listinfo/gmsh</a>
</pre>
</blockquote>
<pre wrap="">
—
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
<a class="moz-txt-link-freetext" href="http://www.montefiore.ulg.ac.be/~geuzaine">http://www.montefiore.ulg.ac.be/~geuzaine</a>
Free software: <a class="moz-txt-link-freetext" href="http://gmsh.info">http://gmsh.info</a> | <a class="moz-txt-link-freetext" href="http://getdp.info">http://getdp.info</a> | <a class="moz-txt-link-freetext" href="http://onelab.info">http://onelab.info</a>
</pre>
</blockquote>
<br>
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