# [Gmsh] Gaps and overlaps when using extrude command

Bart Deschoolmeester bart.deschoolmeester at bbri.be
Sat Aug 15 12:25:42 CEST 2020

```Thanks again, Jeremy.
You seem to have nailed the origin of the problem.
It still feels as a bug to me that reloading a script one just created, gives a different result.
Or am I missing something on how GMSH works?

Stranger still:
Action 1:
Load the file below (without Coherence in the script).
Click: 3D then Coherence then again 3D. This gives an error.
Action 2:
Load the file below (without Coherence in the script).
Click: 3D then Coherence then 1D then again 3D. This gives the wanted results.

This seems all unintuitive to me. Am I missing something of the GMSH logic?
e.g. doesn’t clicking on the coherence command, execute that coherence command?

Bart

KanR = DefineNumber[ 0.1, Name "Parameters/KanR" ];
WanD = DefineNumber[ 0.2, Name "Parameters/WanD" ];
KanMeshsize = DefineNumber[ 0.01, Name "Parameters/KanMeshsize" ];
Rectangle(1) = {-2.5, -2.5, 0, 5, 5, 0};
Circle(5) = {0, 0, 0, KanR, 0, 2*Pi};
Curve Loop(2) = {5};
Plane Surface(2) = {2};
BooleanDifference{ Surface{1}; Delete; }{ Surface{2}; Delete; }
Extrude {0, 0, WanD } {
Surface{1};
}
Point(15) = {0, KanR, 0};
Point(16) = {0, KanR-0.05, 0};
Point(17) = {0, KanR-0.05, WanD};
Point(18) = {0, KanR, WanD};
Line(20) = {15, 16};
Line(21) = {16, 17};
Line(22) = {17, 18};
Line(23) = {18, 15};
Curve Loop(24) = {20, 21, 22, 23};
Plane Surface(8) = {24};
Extrude {{0, 0, 1}, {0, 0, 0}, Pi} {
Surface{8}; Layers {10};
}
Field[1] = Distance;
Field[1].EdgesList = {5};
Field[1].NNodesByEdge = 50;
Field[2] = Threshold;
Field[2].DistMax = 2.5;
Field[2].DistMin = 0;
Field[2].IField = 1;
Field[2].LcMax = 0.25;
Field[2].LcMin = KanMeshsize ;

Background Field = 2;

Mesh.CharacteristicLengthExtendFromBoundary = 0;
Mesh.CharacteristicLengthFromPoints = 0;
Mesh.CharacteristicLengthFromCurvature = 0;

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```