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


> On Oct 11, 2021, at 2:53 AM, Hans Hagen <j.hagen@xs4all.nl> wrote:
> 
> On 10/11/2021 6:30 AM, Gavin via ntg-context wrote:
>> Hi List,
>> I made good progress producing fainter pictures in metafun. Here is a uniformly accelerated cow in the style of my book.
>> I abandoned transparency, since I actually don’t want to see through anything. I am using uncolored to get the fade. It works great with a picture that is made with fill and draw, but it doesn’t work with shading. The example below has a flat disk and a round ball. The disk looks fine, but the shaded ball is not surviving the application of inverted / uncolored.
>> \startMPinclusions
>>   picture disk, ball;
>>   disk := image(
>>     fill fullcircle scaled 1cm withcolor .4white;
>>     draw fullcircle scaled 1cm withpen pencircle scaled 0.8pt ;);
>>   ball := image(
>>     fill fullcircle scaled 1cm
>>       withshademethod "circular"
>>       withshadecenter (.25,.25)
>>       withshadecolors (.8white, black);
>>     draw fullcircle scaled 1cm withpen pencircle scaled 0.8pt ;);
>> \stopMPinclusions
>> \startMPpage
>>    draw inverted (disk uncolored .1white) ;
>>    draw inverted (disk uncolored .2white) shifted (0.25cm,0) ;
>>    draw inverted (disk uncolored .5white) shifted (1cm,0) ;
>>    draw disk shifted (2.25cm,0) ;
>>    draw inverted (ball uncolored .1white) shifted (0, -2cm) ;
>>    draw inverted (ball uncolored .2white) shifted (0.25cm, -2cm) ;
>>    draw inverted (ball uncolored .5white) shifted (1cm, -2cm) ;
>>    draw ball shifted (2.25cm, -2cm) ;
>> \stopMPpage
>> Same result in LMTX and MkIV. (ConTeXt  ver: 2021.09.17 10:01 LMTX  fmt: 2021.9.21  int: english/english)
>> I’m pretty happy with this uncolored trick, and will be even happier if I can get it to work with the shadings.
>> Any suggestions?
> \startMPpage
>    fill fullcircle scaled 10cm
>        shifted (3cm,0)
>        withcolor white ;
>    fill fullcircle scaled 10cm
>        shifted (3cm,0)
>        withcolor black
>        withtransparency (1,.25) ;
> 
>    fill fullcircle scaled 5cm
>        shifted (3cm,0)
>        withcolor .25[red,white] ;
> \stopMPpage
> 
> 
> -----------------------------------------------------------------
>                                          Hans Hagen | PRAGMA ADE
>              Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
>       tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
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