# [Gmsh] nodes inconsistency between 2D and 3D meshing

valentina carapella vcarapella at gmail.com
Wed Jan 25 16:40:44 CET 2012

```Hi all,

I am trying to produce a tetrahedral mesh of half of a  thick-walled
prolate spheroid. To do this, I've first generated the geometry by adapting
an example I found in the gmsh wiki. My script is included below. Then I
run the 3D meshing algorithm based on MeshAdapt for 2D and Delaunay for
3D.
The problem I encounter is that a few nodes that are used to generate the
triangular faces are then not used to generate any of the tetrahedral
elements. Is there a way to avoid this? It's fundamental for the later use
of the mesh within another tool that all the nodes defining triangular
faces are part of one of the tetrahedra of the 3D mesh.

Thanks

Valentina

Thick-Walled Prolate Spheroid Script

lc = 0.09; //this value changes the resolution of the mesh
lz_o = 1; // outer long axis
lx_o = 0.5; // outer radius
wt=0.15;
lz_i=lz_o-wt; //inner long axis

Point(1) = {0,0,0,lc};
Point(2) = {lx_o,0,0,lc};
Point(3) = {0,0,-lz_o,lc};
Point(4) = {lx_i,0,0,lc};
Point(5) = {0,0,-lz_i,lc};
Ellipse(1) = {2,1,3,3};
Ellipse(2) = {4,1,5,5};

//OUTER ELLIPSOID

Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{1};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{3};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{6};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{9};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{12};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{15};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{18};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{21};
}

//INNER ELLIPSOID

Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{2};
}

Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{27};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{30};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{33};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{36};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{39};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{42};
}
Extrude {{0,0,1}, {0,0,0}, Pi/4} {
Line{45};
}

//Upper lines connecting inner and outer half spheroid and the related
surfaces

Line(51) = {16, 9};
Line(52) = {15, 8};
Line(53) = {14, 7};
Line(54) = {13, 6};
Line(55) = {4, 2};
Line(56) = {19, 12};
Line(57) = {18, 11};
Line(58) = {17, 10};
Line Loop(59) = {40, 58, -16, -51};
Plane Surface(60) = {59};
Line Loop(61) = {51, -13, -52, 37};
Plane Surface(62) = {61};
Line Loop(63) = {52, -10, -53, 34};
Plane Surface(64) = {63};
Line Loop(65) = {53, -7, -54, 31};
Plane Surface(66) = {65};
Line Loop(67) = {54, -4, -55, 28};
Plane Surface(68) = {67};
Line Loop(69) = {55, -25, -56, 49};
Plane Surface(70) = {69};
Line Loop(71) = {56, -22, -57, 46};
Plane Surface(72) = {71};
Line Loop(73) = {57, -19, -58, 43};
Plane Surface(74) = {73};
Plane Surface(75) = {59};
Surface Loop(76) = {14, 17, 20, 23, 26, 5, 8, 11, 64, 62, 38, 41, 44, 47,
50, 29, 32, 35, 66, 68, 70, 72, 74, 60};
Volume(77) = {76};
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```