# [Gmsh] Merging two interesting surfaces as one surface

```Dear Gmsh team,
```
```
I am trying to transform a set of spline function into thin surfaces that can
be given one physical group.
I am using extrude function to make these splines to have specific thickness so
that it becomes a surface.
However the resulting surface from extrude cannot be fused together. My problem
in a simplified code:
Is there a easy way in gmsh to convert set of splines to become surface with
specific thickness ?  Kindly
let me know ?

// mesh size description

cl_1   =  5;
cl_2   =  3.000000e-01;
r   =  0.5;

// Define Segment coordinates

X1
={0,0.000811,0.001097,0.001233,0.00129,0.001325,0.001335,0.001343,0.001346,0.001347,0.001348,0.001348,0.001349,0.001349,0.001349,0.001349,0.001349,0.001349,0.001349,0.0013487};
Y1
={0,-2.4,-4,-5.6,-7.2,-8.8,-10.4,-12,-13.6,-15.2,-16.8,-18.4,-20,-21.6,-23.2,-24.8,-26.4,-28,-28.96,-29.118};

X2 ={0.0002703,1.276,1.564,1.433,1.302,1.171,1.04,0.9087,0.7122,0.71171};
Y2 ={-0.8,-0.8009,-1.366,-2.351,-3.335,-4.32,-5.305,-6.29,-7.767,-7.7709};

// Define 1 segment

LN = 90;
nR = #X1[];
p0  =  newp;
p   =  p0;
For i In {0:nR-1}
Point(newp)  =    {X1[i], Y1[i], 0, cl_2};
EndFor
p2  =  newp-1;
Spline(LN)   =  {p:p2};
Extrude {r, r, 0} { Line{LN};}

// Define 2 segment

LN = 95;
nR = #X2[];
p0  =  newp;
p   =  p0;
For i In {0:nR-1}
Point(newp)  =    {X2[i], Y2[i], 0, cl_2};
EndFor
p2  =  newp-1;
Spline(LN)   =  {p:p2};
Extrude {r, r, 0} { Line{LN};}

BooleanUnion(100) = { Surface {1}; Delete; }{ Surface {2}; Delete; };
Physical Surface(1) = {100};

________________________________
Best Regards,

Sathyanarayan Rao, PhD student
Earth and Life Institute/Environmental Sciences (ELI-e)
Université catholique de Louvain
c.037, Croix du Sud 2, Louvain-la-Neuve, Belgium
Phone: 010473827 ( intercom 73827)

________________________________
```
```_______________________________________________
gmsh mailing list
gmsh@onelab.info
http://onelab.info/mailman/listinfo/gmsh
```