[Gmsh] Problem defining a compound geometry

[Harish Narayanan]

On 12/9/11 1:23 PM, David Colignon wrote:
> 
> On 09/12/11 11:45, Harish Narayanan wrote:
> 
>> Hello all,
>>
>> I am having difficulty defining compound geometries. The problem I
>> originally experienced was for a more complicated union of volumes, but
>> the same issue shows up for the simple following case involving trying
>> to merge two unit squares.
>>
>> lc = 0.25;
>>
>> Point(1) = {0, 0, 0, lc};
>> Point(2) = {1, 0, 0, lc};
>> Point(3) = {1, 1, 0, lc};
>> Point(4) = {0, 1, 0, lc};
>>
>> Line(1) = {1, 2};
>> Line(2) = {2, 3};
>> Line(3) = {3, 4};
>> Line(4) = {4, 1};
>> Line Loop(5) = {1, 2, 3, 4};
>>
>> Plane Surface(6) = {5};
>> Translate {-0.5, -0.5, 0.0} {
>>      Duplicata{Surface{6};}
>> } // Surface(7)
>> Compound Surface (8) = {6, 7};
>>
>> //Mesh.RemeshAlgorithm=1;
>>
>> 1. If I try the code above without Mesh.RemeshAlgorithm set to 1, Gmsh
>> crashes with:
>>
>> Info    : Meshing surface 8 (Compound surface, MeshAdapt)
>> Warning : Wrong topology: Genus=-1, Nb boundaries=2, AR=1.5
>> Error   : For remeshing your geometry, you should enable the automatic
>> remeshing algorithm.
>> Error   : Add 'Mesh.RemeshAlgorithm=1;' in your geo file or through the
>> Fltk window (Options>  Mesh>  General)
>>
>> 2. If I try it Mesh.RemeshAlgorithm set to 1, Gmsh seemingly hangs while
>> attempting to complete the meshing process.
>>
>> Could someone please help me understand what is going on? I am assuming
>> that Compound Surface (and Volume) are meant to take unions of
>> geometries. Have I misunderstood what they are for?
> 
> 
> Hi Harish,
> 
> yes, Gmsh is not a solid modeler and cannot take union of surfaces/volumes.
> 
> For the meaning of "Compound" , see
> 
> https://geuz.org/trac/gmsh/wiki/STLRemeshing  (username: gmsh, password:
> gmsh)

Thank you for informing me. I will try to figure out another way of
defining my geometry.

Harish