[Gmsh] curved mesh and jacobian

Christophe Geuzaine cgeuzaine at uliege.be
Wed Nov 4 09:10:32 CET 2020

> On 29 Oct 2020, at 17:49, françois fraysse <francois.fraysse at hotmail.fr> wrote:
> 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 ? 

The value is not exact, but the validity check is a provable bound, i.e. we we report that the element is correct it should be. Can you run the AnalyseMeshQuality plugin and check the results?


> Thank you for developing such a great software :) 
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Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 

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