[Gmsh] Gmsh to Getdp without GEO files

[Christophe Geuzaine]

On 02 Sep 2014, at 23:29, Erroll Brady <erroll.brady at schafercorp.com> wrote:

> Hello 'Anyone that may answer',
>  
> Gmsh seems to mesh Step files accurately but does not accurately create geo files.
>  

Hi Erroll,

You should not try to "export" a STEP file as a GEO file. The "Save as unrolled GEO file" feature is there mainly for debugging purposes: by design Gmsh never translates from one CAD format to another: it can mesh CAD files natively without translation. (The reason for this design choice is that not all CAD formats support all features, and you pretty much always loose stuff when you translate. In particular the GEO CAD kernel is extremely limited, and designed for simplicity; it does not support NURBS patches so it cannot translate all that's available in the STEP spec.)

So if you have a STEP file, just mesh it and add any additional constraints in a .geo file that "merges" that STEP file, e.g. :

Merge "file.step" ;
Physical Surface(1) = {1,4,5};
Physical Volume(2) = {1};

and you are done.


> If the 'Options->General->Enable mouse hover over meshes' is  checked when looking at a meshed step file in Gmsh and mesh 'Surface edges' are displayed, 'Plane'-numbers can be indicated via the mouse hover (See Figure 1). Similarly, if mesh 'Volume edges' are displayed, 'Unknown'-numbers are indicated that I believe are volume-numbers (See Figure 2).
> <image001.jpg>
> To avoid manually correcting geo files that were inaccurately created by Gmsh and then retrofitting physical-surfaces and physical-volumes into the geo file, is it possible to pass these 'Plane'-numbers and 'Unknown'-numbers obtained by manual inspection to a solver (Getdp for example) via an input file? Where can I find information on how to correct syntax to do this?
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine