Gmsh & FC Coordinate resolution.

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keithsloan52
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Gmsh & FC Coordinate resolution.

Post by keithsloan52 »

Because we want features and options not available via the FreeCAD Gmsh functions we use the Gmsh python library direct.

We have encountered some problems all be it resolvable ones, in that it appears Gmsh deals with a finer coordinate resolution than FreeCAD.
Is this something that FC developers have also had to also deal with? or does it avoid such things because it only creates Triangular Meshes?
i.e. If somebody chooses an option that Gmsh creates as a Quad Facet, FC always converts to two Triangular

@wmayer
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Re: Gmsh & FC Coordinate resolution.

Post by wmayer »

A few more details wouldn't be bad.
FC always converts to two Triangular
No, at least not in FEM when the option Quad is set. It only does it when using in the Mesh wb because this only supports triangular meshes.
keithsloan52
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Re: Gmsh & FC Coordinate resolution.

Post by keithsloan52 »

With monte carlo simulations one does not want a fine Mesh, what is required is a minimum mesh that still represents a Shape,
trivial example would be a cube, one wants 6 Quads not 12 Triangle

GDML supports Tessellation with Quad and Triangular Facets
We are using a newish facility/option to create an STL mesh and then combine Facets that are coplanar to create Quad's.
One issue is that what Gmsh is determining to be coplaner is not when we go to create the Quad in FreeCAD.
See the last item of https://gitlab.onelab.info/gmsh/gmsh/-/issues/1726

Another issue is see last item of https://github.com/KeithSloan/GDML/issues/97
The strange mesh is being caused by Gmsh creating a Triangular Facet, that is too small for FC.

I think these problems are arising because when Gmsh calculates the Mesh it is using finer coordinates that FC.
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