[Gmsh] Sharp corners and physicals in .stl

[Martin Vymazal]

Hi Felipe, 

 I didn't manage to mesh your geometry. I'm getting this (after 2 hours of running gmsh):

 Volume do not match  1.588845063218419E-04  1.600196016669183E-04  
7.093476881907630E-03
Volume do not match  1.588932327064256E-04  1.600300053984631E-04  
7.103497179838322E-03
Volume do not match  1.589864934028117E-04  1.601523686854313E-04  
7.279787943128194E-03
Volume do not match  1.589450067262323E-04  1.601000560689481E-04  
7.214546772040652E-03
Volume do not match  1.590410579932190E-04  1.601855161516023E-04  
7.144579521784781E-03
Volume do not match  1.590582035727257E-04  1.602001491852048E-04  
7.128243127657754E-03
Volume do not match  1.588969703174746E-04  1.600347350034682E-04  
7.109485862359648E-03
Volume do not match  1.590485099915781E-04  1.601891519519827E-04  
7.120594288097972E-03
Volume do not match  1.590046382981625E-04  1.601481475152607E-04  
7.140321226564688E-03
Volume do not match  1.589345926016806E-04  1.601045520535501E-04  
7.307471504484324E-03
Volume do not match  1.589321060424286E-04  1.600865990877137E-04  
7.211678253297149E-03
Volume do not match  1.590316228003549E-04  1.601823800873328E-04  
7.184044127390844E-03

Maybe you don't have the same error, though. I have svn revision 14842.

 About stl and physicals: if you need to save only a part of your geometry, make only that part 
physical. If you want to save all surfaces, but in different files, repeating the above with setting 
different surfaces as 'physical' will probably not work because the mesh algorithm is not 
deterministic - if you run gmsh twice, the output mesh is not necessarily exactly identical. So if 
you mark one surface in your geo as physical, save the stl, then mark another surface as 
physical and re-run gmsh to save another stl, you might end up with nonconforming output 
surfaces.
 Maybe you could write the whole mesh as *.msh, and then see if in the gui you cannot remove 
all physical groups but one. By that I mean that you would just remove the physical tag, not the 
surface itself. Then you could export to stl. After that, you reopen your msh and repeat with 
another surface. Not very automatic but I don't have a better idea for the moment.

Best regards,

    Martin



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