# [Gmsh] restrict field

Stéphane BLANCHET stephane.blanchet at esstin.uhp-nancy.fr
Wed Mar 17 09:05:28 CET 2010

```Hi,

Thank you very much, now I have a better understanding of how works this field.

Regards,

Date: Mon, 15 Mar 2010 15:44:48 +0100
From: David.Colignon at ulg.ac.be
To: stephane.blanchet at esstin.uhp-nancy.fr
Subject: Fwd: Re: [Gmsh] restrict field

-------- Original Message --------

Subject:
Re: [Gmsh] restrict field

Date:
Mon, 15 Mar 2010 13:53:22 +0100

From:
Christophe Geuzaine <cgeuzaine at ulg.ac.be>

To:
David Colignon <David.Colignon at ulg.ac.be>

CC:
Stéphane BLANCHET <stephane.blanchet at esstin.uhp-nancy.fr>, gmsh at geuz.org
PS : the Restrict field is used to restrict the application of another
field to some geometrical entities. In your case the "other field" was
set to 1 (the default value), which caused an infinite recursion. This
has now been fixed in the code.

Here's an example of how you can use the Restrict field:

res1  = 1e-1;
x = 1.0;
y = 0.1;

a0 = newp; Point(a0) = {0,0,0,res1};
a1 = newp; Point(a1) = {-x,0,0,res1};
a2 = newp; Point(a2) = {x,0,0,res1};

la1 = newl; Circle(la1) = {a1,a0,a2};
la2 = newl; Circle(la2) = {a2,a0,a1};

loop = newll; Line Loop(loop) = {la1,la2};

sa = news; Plane Surface(sa) = {loop};

Point(4) = {-2, -2, 0};
Point(5) = {2, -2, 0};
Point(6) = {2, 2, 0};
Point(7) = {-2, 2, 0};
Line(5) = {4, 5};
Line(6) = {5, 6};
Line(7) = {6, 7};
Line(8) = {7, 4};
Line Loop(9) = {7, 8, 5, 6};
Plane Surface(10) = {9, 3};

Field[1] = Attractor;
Field[1].EdgesList = {la1,la2,6};
Field[1].NNodesByEdge = 100;

Field[2] = MathEval;
Field[2].F = Sprintf("F1^2 + %g", res1/4);

Field[3] = Restrict;
Field[3].IField = 2;
Field[3].FacesList = {10};
Field[3].EdgesList = {la1,la2, 5:8};

Field[4] = MathEval;
Field[4].F = "0.2";

Field[5] = Restrict;
Field[5].IField = 4;
Field[5].FacesList = {sa};

Field[6] = Min;
Field[6].FieldsList = {3,5};

Background Field = 6;

Mesh.CharacteristicLengthExtendFromBoundary = 0;

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