PS
# ex15.m4
gen_init

[
n = 10; r = 1
for i = 1 to n-1 do {
  for j = i+1 to n do {
     line from rect_(r,i*twopi_/n) to rect_(r,j*twopi_/n)
     }
  }
 ]
[
 linethick = 2.5
 crad = 1.0
 C: circle rad crad
 g = 0.65
 D: C+(Rect_(crad*g,110))
 rm = crad+distance(C,D)
 for r=lthick to rm by 2*lthick do {
   if r < (1-g)*crad then { circle rad r at D thick r/rm*linethick } \
   else { arc cw from Cintersect(D,r,C,crad) \
     to Cintersect(D,r,C,crad,R) with .c at D thick r/rm*linethick }
   }

 linethick = 1.5
 C: circle invis rad crad with .w at C.e+(0.1,0)
 D: C+(Rect_(crad*g,110))
 a = 1 # fade rate parameter
 for r=lthick to rm by lthick do {
   u = 1-(r/rm*(a*r/rm+(1-a)))
   if r < (1-g)*crad then { circle outlined rgbstring(u,u,u) rad r at D } \
   else { arc cw outlined rgbstring(u,u,u) from Cintersect(D,r,C,crad) \
     thick linethick*1.5 to Cintersect(D,r,C,crad,R) with .c at D
     }
   }
 circle rad C.rad at C
 ] with .w at last [].e+(0.1,0)

PE