# [Gmsh] 3D mesh using threshold

Stéphane BLANCHET stephane.blanchet at esstin.uhp-nancy.fr
Wed Mar 17 12:50:19 CET 2010

```Hello,

I have some difficulties to mesh in 3D my model the way I want.

Here is my .geo:

Point(1) = {175, 0, -160};
Point(2) = {-175, 0, -160};
Point(3) = {-175, 0, 160};
Point(4) = {175, 0, 160};
Point(5) = {-50, 0, -50};
Point(6) = {-50, 0, 50};
Point(7) = {50, 0, -50};
Point(8) = {50, 0, 50};
Point(9) = {175, -250, -160};
Point(10) = {-175, -250, -160};
Point(11) = {-175, -250, 160};
Point(12) = {175, -250, 160};
Point(13) = {175, -130, 50};
Point(14) = {175, -30, 50};
Point(15) = {175, -130, 150};
Point(16) = {175, -30, 150};
Point(17) = {-100, -250, -120};
Point(18) = {-100, -250, -140};
Point(19) = {100, -250, -140};
Point(20) = {100, -250, -120};
Point(21) = {-100, -400, -140};
Point(22) = {-100, -400, -120};
Point(23) = {100, -400, -120};
Point(24) = {100, -400, -140};
Point(25) = {375, -30, 50};
Point(26) = {375, -130, 50};
Point(27) = {375, -130, 150};
Point(28) = {375, -30, 150};
Point(29) = {-50, -100, -50};
Point(30) = {-50, -100, 50};
Point(31) = {50, -100, -50};
Point(32) = {50, -100, 50};
Line(1) = {1, 2};
Line(2) = {2, 3};
Line(3) = {3, 4};
Line(4) = {4, 1};
Line(5) = {5, 6};
Line(6) = {7, 5};
Line(7) = {8, 7};
Line(8) = {6, 8};
Line(9) = {1, 9};
Line(10) = {9, 10};
Line(11) = {2, 10};
Line(12) = {10, 11};
Line(13) = {3, 11};
Line(14) = {11, 12};
Line(15) = {4, 12};
Line(16) = {12, 9};
Line(17) = {13, 14};
Line(18) = {15, 13};
Line(19) = {16, 15};
Line(20) = {14, 16};
Line(21) = {17, 18};
Line(22) = {18, 19};
Line(23) = {19, 20};
Line(24) = {20, 17};
Line(25) = {18, 21};
Line(26) = {22, 21};
Line(27) = {17, 22};
Line(28) = {23, 22};
Line(29) = {20, 23};
Line(30) = {24, 23};
Line(31) = {19, 24};
Line(32) = {21, 24};
Line(33) = {14, 25};
Line(34) = {26, 25};
Line(35) = {13, 26};
Line(36) = {27, 26};
Line(37) = {15, 27};
Line(38) = {28, 27};
Line(39) = {16, 28};
Line(40) = {25, 28};
Line(41) = {5, 29};
Line(42) = {29, 30};
Line(43) = {6, 30};
Line(44) = {7, 31};
Line(45) = {31, 29};
Line(46) = {8, 32};
Line(47) = {32, 31};
Line(48) = {30, 32};
Line Loop(1) = {1, 2, 3, 4, 5, 8, 7, 6};
Plane Surface(1) = {1};
Line Loop(2) = {1, 11, -10, -9};
Plane Surface(2) = {2};
Line Loop(3) = {2, 13, -12, -11};
Plane Surface(3) = {3};
Line Loop(4) = {3, 15, -14, -13};
Plane Surface(4) = {4};
Line Loop(5) = {4, 9, -16, -15, 17, 20, 19, 18};
Plane Surface(5) = {5};
Line Loop(6) = {10, 12, 14, 16, 21, 22, 23, 24};
Plane Surface(6) = {6};
Line Loop(7) = {21, 25, -26, -27};
Plane Surface(7) = {7};
Line Loop(8) = {24, 27, -28, -29};
Plane Surface(8) = {8};
Line Loop(9) = {23, 29, -30, -31};
Plane Surface(9) = {9};
Line Loop(10) = {22, 31, -32, -25};
Plane Surface(10) = {10};
Line Loop(11) = {26, 32, 30, 28};
Plane Surface(11) = {11};
Line Loop(12) = {17, 33, -34, -35};
Plane Surface(12) = {12};
Line Loop(13) = {18, 35, -36, -37};
Plane Surface(13) = {13};
Line Loop(14) = {19, 37, -38, -39};
Plane Surface(14) = {14};
Line Loop(15) = {20, 39, -40, -33};
Plane Surface(15) = {15};
Line Loop(16) = {34, 40, 38, 36};
Plane Surface(16) = {16};
Line Loop(17) = {5, 43, -42, -41};
Plane Surface(17) = {17};
Line Loop(18) = {6, 41, -45, -44};
Plane Surface(18) = {18};
Line Loop(19) = {7, 44, -47, -46};
Plane Surface(19) = {19};
Line Loop(20) = {8, 46, -48, -43};
Plane Surface(20) = {20};
Line Loop(21) = {42, 48, 47, 45};
Plane Surface(21) = {21};
Surface Loop(1) = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21};
Volume(1) = {1};

lc=5;

Field[1] = Attractor;
Field[1].EdgesList = {48, 47, 45, 42};

Field[2] = MathEval;
Field[2].F = "3";

Field[3] = Restrict;
Field[3].IField = 2;
Field[3].FacesList = {21};

Field[4] = Threshold;
Field[4].IField = 1;
Field[4].LcMin = 3;
Field[4].LcMax = 10;
Field[4].DistMin =0;
Field[4].DistMax = 50;

Field[5] = Min;
Field[5].FieldsList = {3,  4};

Background Field = 5;

The 2D mesh gives me the result I want: a uniform mesh on the surface 21, and the same size of mesh on the other surfaces.

But for the 3D mesh, what I want is the result of the threshold field on the surface 21. I know I can't define this surface as an attractor since it doesn't work so well with surfaces. So please, if you have any idea for my problem...

regards

---------------

BLANCHET Stéphane

Elève-Ingénieur ESSTIN (5 Année)
Option: Mécanique des Fluides et Énergétique

Tél: 0632224601
Mail: stephane.blanchet at esstin.uhp-nancy.fr

Ecole Supérieure des Sciences et Technologies de l'Ingénieur de Nancy
Université Henri Poincaré Nancy I
2, rue Jean Lamour
54 519 - Vandoeuvre Lès Nancy

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