2011/5/2 Andreas Puettmann <[email protected]>: > Hi all! > > I have been experiencing weird problems with some GMSH generated tetra > meshes. After some testing I was able to boil it down to the following > strange behavior: > > I create a cylinder with a very simple .geo file. For meshing and exporting > of the mesh in ASCII format via the GUI I tried different approaches: > > Meshing: > First option: Click only the "3D" button > Second option: Click "1D" "2D" "3D" successively > > Saving: > First option: "File->Save Mesh" > Second option: "File->Save as" + "save all (ignore physical groups)" > activated > Third option: "File->Save as" + "save all (ignore physical groups)" not > activated > > The funny thing is that any of the 6 possible combinations produce a > different .msh file, i.e. different numbers of nodes and elements. Is really > neither of these 6 supposed to result in identical files? > > So, I would really appreciate some info on the differences between the > different approaches. Especially: > What exactly is the difference between the two meshing options? Doesn't > clicking "3D" just do the same as 1D-2D-3D? > And what is the difference between the first and the third saving option? I > would think they should be just the same... > > I am attaching the .geo file, and the 6 mesh files. Their file names may be > read as: > _3D : meshing option 1 > _123: meshing option 2 > > _SM: saving option 1 (save mesh) > _SA_ig: saving option 2 (save as + ignore phys. gr.) > _SA: saving option 3 (save as + do not ignore phys. gr.) > > Thanks for any help! > Andreas
Hello. I believe Gmsh's meshing algorithms are random, so even repeating identically the meshing and saving options might give you a different mesh. It should be equivalent though, with roughly the same number of elements; this seems to be the case for your examples, they're all within about ten or twenty percent. Is this equivalence sufficient for your application? Many meshing algorithms do involve a random element; see, e.g., Persson, P.-O., & G. Strang (2004). A simple mesh generator in MATLAB. SIAM Review 46 (2), 329-345. <http://dx.doi.org/10.1137/S0036144503429121> The second saving option is quite different though, not equivalent, if you have defined physical groups. _______________________________________________ gmsh mailing list [email protected] http://www.geuz.org/mailman/listinfo/gmsh
