h = 1;
Mesh.RecombineAll = 1;

L1 = h; // x length
L2 = 2*h; // y length
L3 = 3*h; // z length

N1 = 8; // nodes in x
N2 = 4; // nodes in y
N3 = 2; // nodes in z




Point(1) = {-L1/2,-L2/2,-L3/2};
Point(2) = {L1/2,L2/2,L3/2};
Point(3) = {-L1/2,-L2/2,L3/2};
Point(4) = {-L1/2,L2/2,-L3/2};
Point(5) = {L1/2,-L2/2,-L3/2};
Point(6) = {L1/2,L2/2,-L3/2};
Point(7) = {L1/2,-L2/2,L3/2};
Point(8) = {-L1/2,L2/2,L3/2};
Line(1) = {3, 7};
Line(2) = {7, 5};
Line(3) = {5, 1};
Line(4) = {1, 3};
Line(5) = {3, 8};
Line(6) = {8, 4};
Line(7) = {4, 6};
Line(8) = {6, 2};
Line(9) = {2, 8};
Line(10) = {1, 4};
Line(11) = {6, 5};
Line(12) = {7, 2};
Line Loop(13) = {9, 6, 7, 8};
Plane Surface(14) = {13};
Line Loop(15) = {4, 1, 2, 3};
Plane Surface(16) = {15};
Line Loop(17) = {3, 10, 7, 11};
Plane Surface(18) = {17};
Line Loop(19) = {10, -6, -5, -4};
Plane Surface(20) = {19};
Line Loop(21) = {11, -2, 12, -8};
Plane Surface(22) = {21};
Line Loop(23) = {9, -5, 1, 12};
Plane Surface(24) = {23};
Surface Loop(25) = {24, 14, 20, 18, 16, 22};
Volume(26) = {25};

Transfinite Line {9, 7, 3, 1} = N1 ;
Transfinite Line {5, 10, 11, 12} = N2 ;
Transfinite Line {4, 6, 2, 8} = N3 ;
Transfinite Surface {14,16,18,20,22,24};
Transfinite Volume {26};

