# Definition of the subdomain error

Hello fellow users,

I’m looking to create a mesh using a boundary from the alphabet R. I have successfully created the border geometry using respective parametric equations as shown in the picture and plot it.

My problem is when I used the function

mesh Th = buildmesh(…);

using the same equations, it gives me this error:

`FreeFem++ v4.1 (Sat, Nov 13, 2021 7:40:01 PM - git v4.10)
file : D:\Documents\Docs\Semester 8\Fenomena Transpor di Biomedika\Kuliah 6\r.edp
1 : // outer border
2 : border v1(t=0,5.5){ x=0; y=t; label=1;};
3 : border h1(t=0,4){ x=t; y=5.5; label=2;};
4 : border c1(t=pi/2,-pi/2){ x=1.75cos(t)+4; y=1.75sin(t)+3.75; label=3;};
5 : border d2(t=4,5){ x=t; y=-2t+10; label=4;};
6 : border h4(t=5,3.5){ x=t; y=0; label=5;};
7 : border d1(t=3.5,2.5){ x=t; y=-2
t+7; label=6;};
8 : border h3(t=2.5,1.5){ x=t; y=2; label=7;};
9 : border v2(t=2,0){ x=1.5; y=t; label=8;};
10 : border h2(t=1.5,0){ x=t; y=0; label=9;};
11 : // inner border
12 : border v3(t=3,4.5){ x=1.5; y=t; label=10;};
13 : border h6(t=1.5,3.5){ x=t; y=4.5; label=11;};
14 : border c2(t=pi/2,-pi/2){ x=0.75cos(t)+3.5; y=0.75sin(t)+3.75; label=12;};
15 : border h5(t=3.5,1.5){ x=t; y=3; label=13;};
16 :
17 : int n=20;
18 : mesh Th =buildmesh(v1(n)+h1(n)+c1(n)+d2(n)+h4(n)+d1(n)+h3(n)+v2(n)+h2(n)+v3(-n)+h6(-n)+c2(-n)+h5(-n));
19 : plot(Th,wait=1);
20 : sizestack + 1024 =1472 ( 448 )

Error in the definition of subdomain 4 boundary border 9/13: wrong direction 80 1
Error in the definition of subdomain 5 boundary border 8/13: wrong direction 100 1
Error in the definition of subdomain 6 boundary border 7/13: wrong direction 120 1
Error in the definition of subdomain 7 boundary border 6/13: wrong direction 140 1
Error in the definition of subdomain 8 boundary border 5/13: wrong direction 160 1
Error in the definition of subdomain 9 boundary border 4/13: wrong direction 180 1
Error in the definition of subdomain 10 boundary border 3/13: wrong direction 200 1
Error in the definition of subdomain 11 boundary border 2/13: wrong direction 220 1
Error in the definition of subdomain 12 boundary border 1/13: wrong direction 240 1
Fatal error in the mesh generator 777
current line = 2
Meshing error: Bamg
number : 777,
catch Err bamg
Meshing error: Bamg
number : 777`

Where did I went wrong? The borders seems to have no problem for me, thanks in advance!

Remenber in 2d the border see as in direct sens by default ( the domain must be a left of the orient
border) or put a negative number of segment to reverse this rule.

THE CORRECTION

`````` border v1(t=0,5.5){ x=0; y=t; label=1;};
border h1(t=0,4){ x=t; y=5.5; label=2;};
border c1(t=pi/2,-pi/2){ x=1.75*cos(t)+4; y=1.75*sin(t)+3.75; label=3;};
border d2(t=4,5){ x=t; y=-2*t+10; label=4;};
border h4(t=5,3.5){ x=t; y=0; label=5;};
border d1(t=3.5,2.5){ x=t; y=-2*t+7; label=6;};
border h3(t=2.5,1.5){ x=t; y=2; label=7;};
border v2(t=2,0){ x=1.5; y=t; label=8;};
border h2(t=1.5,0){ x=t; y=0; label=9;};
// inner border
border v3(t=3,4.5){ x=1.5; y=t; label=10;};
border h6(t=1.5,3.5){ x=t; y=4.5; label=11;};
border c2(t=pi/2,-pi/2){ x=0.75*cos(t)+3.5; y=0.75*sin(t)+3.75; label=12;};
border h5(t=3.5,1.5){ x=t; y=3; label=13;};

int n=20;
plot(v1(n)+h1(n)+c1(n)+d2(-n)+h4(n)+d1(n)+h3(n)+v2(n)+h2(n)+v3(-n)+h6(-n)+c2(-n)+h5(-n),wait=1);
mesh Th =buildmesh(v1(-n)+h1(-n)+c1(-n)+d2(-n)+h4(-n)+d1(-n)+h3(-n)+v2(-n)+h2(-n)+v3(n)+h6(n)+c2(n)+h5(n));
plot(Th,wait=1);

``````
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