OpenSCAD Rounded poly disk example. Different radii for xy vs z

rounded_poly_disk.scad

n = 8;
height = 40;

width = 50; // distance across flats of polygon (when n is even)
rxy = 8;
rz = 3;
width2 = 30; 
rxy2 = rxy*width2/width;
rz2 = 0.1; // small but nonzero

$fn=5*n;

module rounded_poly_disk(w, rxy, rz, n) {
  R = circumradius(w/2,n)-circumradius(rxy,n);
  a = 360/n;
  hull() rotate(a/2) for(i=[0:n-1]) 
    rotate(a*i) translate([R,0,0])
    rotate(-a/2) rotate_extrude(angle=a) translate([rxy-rz,0]) 
      semicircle(rz);
}

module semicircle(r) {
  intersection() {
    translate([0,-r*1.5]) square(r*3);
    circle(r=r);
  }
}

translate([0,0,rz]) hull() {
  rounded_poly_disk(width,rxy,rz,n);
  translate([0,0,height-rz-rz2]) rounded_poly_disk(width2,rxy2,rz2,n);
}

function circumradius(inradius,n) = inradius/cos(180/n);
function inradius(circumradius,n) = circumradius*cos(180/n);