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

[Andrey]

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.


Ant suggestions?


Best regards,

Andrey


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