> On 23 Mar 2015, at 23:28, Simone GREMMO [531257] <[email protected]> > wrote: > > Thanks for the quick reply, but why this hack is applied if size is 1e22 and > not for example if it is 1e21?
1.e22 is just a "magic number" (the choice is arbitrary)... > The difference between the two values can be practically neglected > considering that the domain bounding box diagonal may be about 1e1 or 1e2. > > I am insisting in this as I am including Gmsh as library in a c++ program and > have had unexpected behaviour because of this "hack" : when defining size > 1e22 or 1e21 the resulting mesh was not the same. > After your explanation I think that i have one possibility: to define this > size arbitrary large but smaller than this "reference" value of 1e22, so that > Gmsh does not try to set this "10 elements in the domain". Just to be > clearer, when generating the mesh with Gmsh I have the constraint that no > vertex should be added on the edges. > > Regards, > Simone > ________________________________________ > De : Christophe Geuzaine [[email protected]] > Envoyé : lundi 23 mars 2015 22.20 > À : Simone GREMMO [531257] > Cc : [email protected] > Objet : Re: [Gmsh] Prescribed mesh size at vertices - strange treatment > >> On 23 Mar 2015, at 21:40, Simone GREMMO [531257] <[email protected]> >> wrote: >> >> Hello, >> I have a question about the way the prescribed mesh size is imposed when >> meshing an edge: in function LC_MVertex_PNTS(GEntity *ge, double U, double >> V) in file ./Mesh/BackgroundMesh.cpp that is used to set l2 (the >> characteristic length from points), it is said that if prescribed mesh size >> at the edge extremities is GREATER than 1e22, then lc=referenceLength / 10; >> where the referenceLength is the diagonal of the domain bounding box. >> >> In the sources there is already a FIXME note (// FIXME we might want to >> remove this to make all lc treatment consistent), but I would like to >> understand from where this arbitrary size comes from. How to ensure that the >> results is always the expected one? >> I would not expect that the resulting mesh depends on the domain >> bounding-box size, or that using 1e22 or 1e21 influences the result . >> > > Indeed, this is a little bit of a "hack". If no characteristic mesh sizes are > provided, the default size is 1e22 (it's arbitrary large; it should actually > be something like MAX_FLOAT). In that case, in order to still get a mesh that > is "reasonable", we set the target element size to "10 elements in the > domain". > > > >> Thanks for your explanations, >> >> Regards, >> Simone >> _______________________________________________ >> gmsh mailing list >> [email protected] >> http://www.geuz.org/mailman/listinfo/gmsh > > -- > Prof. Christophe Geuzaine > University of Liege, Electrical Engineering and Computer Science > http://www.montefiore.ulg.ac.be/~geuzaine > > > > > _______________________________________________ > gmsh mailing list > [email protected] > http://www.geuz.org/mailman/listinfo/gmsh -- Prof. Christophe Geuzaine University of Liege, Electrical Engineering and Computer Science http://www.montefiore.ulg.ac.be/~geuzaine _______________________________________________ gmsh mailing list [email protected] http://www.geuz.org/mailman/listinfo/gmsh
