/**
 *  Trevor P. Irons, XRI Geophysics, LLC
 *  Test of Coloumbic Magnetic Potential
 */

lc = 1e-2;     // Target element size
R  =  .11;     // Minimum Radius
R2 =  .175;    // Minimum Radius
D0 = 9.75;     // Top of mesh
D1 = 11.25;    // Bottom of mesh

////////////////////////////////////
// North Pole

Function Ring

    // centre
    p0 = newp; Point(p0) = {   0,    0, D0, lc};

    // Points defining outer ring
    p1 = newp; Point(p1) = { R,  0, D0, lc};
    p2 = newp; Point(p2) = { 0,  R, D0, lc};
    p3 = newp; Point(p3) = {-R,  0, D0, lc};
    p4 = newp; Point(p4) = { 0, -R, D0, lc};

    c1 = newc; Circle(c1) = {p1, p0, p2};
    c2 = newc; Circle(c2) = {p2, p0, p3};
    c3 = newc; Circle(c3) = {p3, p0, p4};
    c4 = newc; Circle(c4) = {p4, p0, p1};

    // Inner ring
    p5 = newp; Point(p5) = { R2,   0, D0, lc};
    p6 = newp; Point(p6) = {  0,  R2, D0, lc};
    p7 = newp; Point(p7) = {-R2,   0, D0, lc};
    p8 = newp; Point(p8) = {  0, -R2, D0, lc};

    c5 = newc; Circle(c5) = {p5, p0, p6};
    c6 = newc; Circle(c6) = {p6, p0, p7};
    c7 = newc; Circle(c7) = {p7, p0, p8};
    c8 = newc; Circle(c8) = {p8, p0, p5};

    l1 = newl; Line Loop(l1) = {c1, c2, c3, c4, c5, c6, c7, c8};

    s1 = news; Plane Surface(s1) = {l1};
    Extrude {0,0,D1-D0} {
      Surface{s1};
    }

Return

Function Cyl

    // centre
    p0 = newp; Point(p0) = {   0,    0, D0, lc};

    // Points defining outer ring
    p1 = newp; Point(p1) = { R2,   0, D0, lc};
    p2 = newp; Point(p2) = {  0,  R2, D0, lc};
    p3 = newp; Point(p3) = {-R2,   0, D0, lc};
    p4 = newp; Point(p4) = {  0, -R2, D0, lc};

    c1 = newc; Circle(c1) = {p1, p0, p2};
    c2 = newc; Circle(c2) = {p2, p0, p3};
    c3 = newc; Circle(c3) = {p3, p0, p4};
    c4 = newc; Circle(c4) = {p4, p0, p1};

    l1 = newl; Line Loop(l1) = {c1, c2, c3, c4};

    s1 = news; Plane Surface(s1) = {l1};
    Extrude {0,0,D1-D0} {
      Surface{s1};
    }

Return


Call Cyl;
/*
For r In {1:12}
  Call Ring;
  R2 = R;
  R *= 1.2;
  lc *= 1.1;
EndFor
*/