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<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Hello Mark,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Not sure about this, but the reverse all normal command could just be post-processing. This would explain why it is not saved in you mesh file once you update it. I would suggest using the
<i>Reverse Line { line_id } / Surface { surface_id } / “*” </i>command. What it does is reverse the node ordering within a given line, surface, or globally. Since node ordering dictates normal orientations, you should get what you want.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Additionally, there is to my knowledge no way of generating Physical Groups of directly on meshes. Yet, I see two work-arounds. Solution one, is to re-process your msh file outside of Gmsh. A msh
file has a $PhysicalNames section that you can add by hand to define your groups but then you would have to tag each element belonging to the group individually in the $Element section. That could work but that is certainly not practical, see
<a href="http://gmsh.info/doc/texinfo/gmsh.html#MSH-ASCII-file-format">documentation on MSH file format</a> for more information.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Second possibility, have a look at STL remeshing example on the
<a href="https://onelab.info/svn/gmsh/trunk/tutorial/t13.geo">wiki</a> (user: gmsh, password: gmsh). This could be a way to re-create a geometry based on your mesh, apply the Physical group and finally re-save the geometry with the groups.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Hoping this was useful,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Guillaume Dilasser<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="mso-fareast-language:FR">De :</span></b><span style="mso-fareast-language:FR"> gmsh [mailto:gmsh-bounces@ace20.montefiore.ulg.ac.be]
<b>De la part de</b> Mark Smith<br>
<b>Envoyé :</b> lundi 23 janvier 2017 16:52<br>
<b>À :</b> gmsh@onelab.info<br>
<b>Objet :</b> [Gmsh] Reversing mesh normals<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-GB">Hi Gmsh users,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I have a gmsh format mesh produced in pointwise which I load into gmsh. I wish to reverse the direction of the surface normals on the mesh which I do by options>mesh>color>Reverse all normal, if I set mesh.normals to
some non zero value the normal vector is displayed on the surface mesh and reverse all normal does indeed reverse the vectors direction BUT if I save the mesh out to gmsh msh format with the normals reversed then load it back into gmsh the normal direction
is the same as the original, am I doing something wrong or is what I want to do not possible?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Also Is it possible to only reverse the normals on certain mesh surfaces rather than all?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Is there a way to define Physical groups on a mesh rather than on Geometry if one only has a mesh?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"> <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Thanks in advance<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Best regards<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Mark<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span lang="EN-GB" style="font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-language:FR"><o:p> </o:p></span></p>
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