I used “redecorated" to get the pictures with light, solid grays. Below is code for producing just the ball, if anyone wants to see the details. It includes a simple “shadow" macro that produces a shadow of any picture with an adjustable gray.

I’m having lots of metafun!
Gavin


\startMPinclusions
 picture ball;
 ball := image(
   fill fullcircle scaled 1cm
     withshademethod "circular"
     withshadecenter (.25,.25)
     withshadecolors (.8white, black);
   draw fullcircle scaled 1cm withpen pencircle scaled 0.8pt ;);
 vardef shadow(expr p, t) =
   draw redecorated (draw p) withcolor t[background,0.8background];
 enddef;
\stopMPinclusions

\startMPpage
 pair p;
 for i=0 upto 10:
   p := (i*cm/10, -((i-7.33)**2)*cm/7);
   shadow(ball shifted p, (i+1)/10) ;
 endfor
 draw ball shifted(1.1cm, -1.92cm) ;
\stopMPpage