# [Gmsh] Coherence 'could not find extruded vertex' error

Bart Deschoolmeester bart.deschoolmeester at bbri.be
Mon Aug 17 10:16:50 CEST 2020

```Hello,
Sorry to bother everybody again.
I'm a beginner and I seem to run in on one error after another. I'm using GMSH 4.7.0 (I came across GMSH trough the onelab website) on Windows 10.

See the script below (from a bigger 3D project where I try to narrow down the errors I get).
I get a good 3D mesh but at the curve where the two objects meet, the mesh is not aligned.
Using the coherence command I get a large list of errors of the type:
Error : could not find extruded vertex (0.08443279255020152,  -0.053826794978966, 0).

Yet, if I change the point y-coordinates to a positive number:
Point(23) = {0, 0.1, 0};
Point(24) = {0, 0.05, 0};
Point(25) = {0, 0.05, WanD};
Point(26) = {0, 0.1, WanD};

All works as expected.

Thanks for the help.
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(23) = {0, -0.1, 0};
Point(24) = {0, -0.05, 0};
Point(25) = {0, -0.05, WanD};
Point(26) = {0, -0.1, WanD};
Line(32) = {23, 24};
Line(33) = {24, 25};
Line(34) = {25, 26};
Line(35) = {26, 23};
Curve Loop(30) = {34, 35, 32, 33};
Plane Surface(14) = {30};
Extrude {{0, 0, 1}, {0, 0, 0}, Pi} {
Surface{14}; Layers{25};
}

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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```