[Gmsh] curved mesh and jacobian

[françois fraysse]

Hello GMSH users and developers,

I generated a simple quadratic tetrahedra based mesh using default settings with gmsh v4.6.0. After regularizing, minimum jacobian lies between default target, ScaledMinjac=0.102 so mesh seems valid, no warning or errors.

Then in a separate code I post-process the mesh and build quadratic shape functions. I evaluate the determinant of the Jacobian at the 10 nodes of each tetra and it turns out that I get some small values below zero for some tetras : ~1e-2/1e-3.

I do not exclude a mistake in the verification procedure, but I didn't find it so far.

My question is : is ScaledMinJac an exact value or an approximation ?

Thank you for developing such a great software :)
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