Dear Wolfgang,
According to your advice, I am able to make a working example as following.
\usemodule[animation]
\setupinteraction[state=start]
\startuseMPgraphic{Circles}{s}
numeric sn, L, N;
path p, q;
p := fullcircle scaled 72;
L:=length p;
N:=20;
sn := \MPvar{s};
q := subpath (0, sn/N*L) of p;%
draw q withcolor red;
fill fullcircle scaled 3 shifted point length q of q withcolor blue;
setbounds currentpicture to unitsquare shifted (-0.5,-0.5) scaled 75;
\stopuseMPgraphic
\starttext
\startanimation[menu=yes, menucolor=blue, framerate=5]
\dorecurse{20}
{\expanded{\frame{
\useMPgraphic{Circles}{s=\recurselevel}}}}
\stopanimation
\stoptext
One more question.
In metafun document, there is a command \setupMPvariables before
\startuseMPgraphic. But we don’t use it in this example.
Hence I think that it is not necessary always. Is there any case in which we
have set the MPvariables?
Thank you.
Best regards,
Dalyoung
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