for i = 0 upto 8:
a := d * (1 + 1/4 i);
b := a +-+ d;
e := 1 +-+ b/a;
path ee; ee = fullcircle xscaled 2a yscaled 2b rotated r shifted o;
draw ee;
picture tl; tl = thelabel.top(TEX("$e=" & dp(e) & "$"), origin);
draw tl rotated angle direction 2 of ee shifted point 2 of ee;
endfor