# [Gmsh] Compound surface, error: unknown surface + could not make generatrice list

Charlotte Gegout charlottegegout at gmail.com
Thu Mar 17 17:02:54 CET 2016

```Hi, I am pretty new to GMSH and I am trying to create compound surfaces to
mesh several elementary entities (surfaces) of my geometry as one surface.
The goal is basically to avoid degenerated triangles on very narrow
surfaces by merging them together.
Here is my code:

> Merge "UC206N_PAV_SANS-LOUVRES_ENCEINTE_v3.STEP";
>
>
>>
>> Physical Surface(213) = {-2};
>
>
>> Physical Surface(214) = {-1, -3, -4, -5, -6, 7, 8, 9, 10, 11, -12, -13,
>> 14, 15, -16, -17, 18, 19, -20, -21, -22, -23, -24, -25, -26, 27, -28, 29,
>> -30, -31, -32, -33, -34, 35, 36, 37, 38, 39, 40, 41, 42, 43, -44, -45, -46,
>> -47, 48, 49, -50, -51, 52, -53, 54, 55, 56, -57, -58, 59, 60, 61, 62, 63,
>> 64, 65, -66, -67, -68, -69, -70, -71, -72, 73, 74, -75, -76};
>
>
>>
>> Compound Surface(215) = {61, 60, 48, 49, 63, 64, 3, 4, 19, 18, 21, 20,
>> 68, 69, 70, 71, 72, 35, 73, 34, 33, 32, 31, 30, 23, 22, 17, 16, 6, 15, 54,
>> 53, 51, 50, 47, 46};
>
> Compound Surface(216) = {7, 11};
>
> Compound Surface(217) = {38, 39};
>
> Compound Surface(218) = {37, 27, 14};
>
> Compound Surface(219) = {56, 55, 74};
>
>
Unfortunately I get the following error messages:

> Error   : Unknown surface 61
>
> Warning : Could not make generatrices list for compound surface 215
>
> Error   : Unknown surface 7
>
> Warning : Could not make generatrices list for compound surface 216
>
> Error   : Unknown surface 38
>
> Warning : Could not make generatrices list for compound surface 217
>
> Error   : Unknown surface 37
>
> Warning : Could not make generatrices list for compound surface 218
>
> Error   : Unknown surface 56
>
> Warning : Could not make generatrices list for compound surface 219
>
>
I am clueless about what it means since the 'unknown' surfaces are
recognized and meshed properly with no error when I don't use  the compound
surfaces.

Can someone tell me what is happening and how to use Compound surfaces?
If not, does anybody know of an other way to obtain the desired result. I
attached the matching .geo file for more clarity.

Thanks.

Charlotte
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