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

Christophe Geuzaine cgeuzaine at uliege.be
Mon Aug 17 13:16:18 CEST 2020

Dear Bart,

What are you trying to achieve? As Jeremy explained, your geometry is non-conformal. Do you want to create a conformal mesh? If so you'll need to have a conformal geometry first.

Christophe

> On 17 Aug 2020, at 10:16, Bart Deschoolmeester <bart.deschoolmeester at bbri.be> wrote:
>
> 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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—
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine