[Gmsh] GMSH doesn’t want to make grid inside sphere

[Christophe Geuzaine]

Andrey wrote:
> Dear GMSH community!
> 
> 
> Let’s consider the following geometry:
> 
> Input data to GMSH is a triangulated sphere of radius=1.
> 
> Each point of triangulation has constant characteristic length.
> 
> 
> I pass triangulated sphere to GMSH in order to get meshed volume inside:
> 
> 
> gmsh-win.exe -3 boundary.geo -o mesh.mesh -format mesh -order 1 -algo 
> iso -optimize
> 
> 
> Then I consider two different cases (input geometry is the same, the 
> only difference is characteristic length):
> 
> 
> 1) If characteristic length=0.025 – everything is OK.
> 
> See attached input: boundary_good.zip and produced: sphere_good.png
> 
> Output of quality for this case:
> 
> Info : Opti : 0.00 < QUAL < 0.10 : 0 elements
> 
> Info : Opti : 0.10 < QUAL < 0.20 : 0 elements
> 
> Info : Opti : 0.20 < QUAL < 0.30 : 8 elements
> 
> Info : Opti : 0.30 < QUAL < 0.40 : 113 elements
> 
> Info : Opti : 0.40 < QUAL < 0.50 : 3134 elements
> 
> Info : Opti : 0.50 < QUAL < 0.60 : 112218 elements
> 
> Info : Opti : 0.60 < QUAL < 0.70 : 285051 elements
> 
> Info : Opti : 0.70 < QUAL < 0.80 : 389672 elements
> 
> Info : Opti : 0.80 < QUAL < 0.90 : 184604 elements
> 
> Info : Opti : 0.90 < QUAL < 1.00 : 15858 elements
> 
> 2) If characteristic length=0.05 – produced mesh is not correct.
> 
> See attached input: boundary_bad.zip and produced: sphere_bad.png
> 
> Output of quality for this case:
> 
> Info : Opti : 0.00 < QUAL < 0.10 : 0 elements
> 
> Info : Opti : 0.10 < QUAL < 0.20 : 2707 elements
> 
> Info : Opti : 0.20 < QUAL < 0.30 : 2033 elements
> 
> Info : Opti : 0.30 < QUAL < 0.40 : 923 elements
> 
> Info : Opti : 0.40 < QUAL < 0.50 : 649 elements
> 
> Info : Opti : 0.50 < QUAL < 0.60 : 670 elements
> 
> Info : Opti : 0.60 < QUAL < 0.70 : 606 elements
> 
> Info : Opti : 0.70 < QUAL < 0.80 : 425 elements
> 
> Info : Opti : 0.80 < QUAL < 0.90 : 174 elements
> 
> Info : Opti : 0.90 < QUAL < 1.00 : 15 elements
> 
> 
> Summary:
> 
> First case is more complex, because of larger amount of produced 
> tetrahedra and because 2D-frames (of input data) are also meshed by GMSH 
> (according to characteristic lengths). But first case is handled 
> correctly, the second - not.
> 

This is weird: I cannot reproduce the problem on my machine... Does it
still happen with recent nightly snapshots?


> 
> Ant suggestions?
> 
> 
> Best regards,
> 
> Andrey
> 
> 
> 
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> 
> 
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> 
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> 
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine