[Gmsh] Preservation of physical surface labels after boolean operation

[Uģis Lācis]

Hi,

I would like to express my gratitude for implementation of the new 
OpenCASCADE geometry kernel, it is really useful and make many things 
much easier.

Do you have any update with respect to boolean operation and physical 
surface labels? It would be very useful, if physical surface labels 
could be kept for surface part which is not modified, while the newly 
created surface could inherit the label from the tool object.

If this feature is still not implemented, could there be some workaround 
to, for example, track surface labels, as cube is subtracted form 
another cube?

Best,
Ugis

On 15/04/17 20:03, Christophe Geuzaine wrote:
> Hi Andrew,
>
> It's not yet implemented, but it's clearly on our TODO list. (Currently we already preserve the tags of the highest-dimensional entities whenever possible: cf. demos/boolean/fragments_numbering.geo.)
>
> Christophe
>
>> On 15 Apr 2017, at 19:39, andrew <armitatz at gmail.com> wrote:
>>
>>
>> Hi,
>>
>> The new gmsh 3 is great with the Boolean additions!.
>>
>> I would like to ask if there is a way to preserve the labeling of the physical surfaces of the objects and the tool objects before the Boolean operation and pass them to the new objects after the Boolean operation.
>>
>> For example in the following geo file there is a main object (b1[]) from extrusion and 3 tool objects (b2[],b3[],b4[]) created from extrusion.
>>
>>  From these objects I define two physical surfaces (b1[2]=out - plane 5 /b2[3]=inside - plane 11). If I perform a Boolean operation with them I lose the out/inside names and since the numbering of the surfaces changes from the creation of new objects I can't find the inside/out labels any more. Is there a way to preserve the names from the old objects and pass them to the new object? For example the newly created surfaces (plane 40 - plane 25) in the new object that were part of the out surface before could be preserved.
>>
>> Something like: Physical Surface("new_out")=FromOld("out") that could assing to the surfaces 40 & 25 the tag 'out' from the surface 5 since these two were created from the breaking of surface 5.
>>
>> kind regards
>>
>> Andrew Tsiantis
>>
>>
>>
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