Hi,
On Sat, Jul 19, 2025 at 2:42 AM Jeong Dal via ntg-context
<ntg-context@ntg.nl> wrote:
>
> Dear all,
>
> I tried to make an animation which draws Cardioid curve.
> I found a code which draws Cardioid using circles.
> Since I’d like to draw it differently, I modified it a little.
>
> 1. Define the z[] values in the \startMPdefinitions block
> 2. Modified the drawing method in \startMPbuffer
>
> When I run it, it doesn’t recognize the z[] values defined already.
> I think that the z[] values are not delivered to \startbuffer.
> I tried \startMPinclusions, \startMPinitialization, but I couldn’t succeed.
>
> 1. How can I deliver the z[] values into the buffer?
> 2. What is wrong in the following code?
>
> Thank you for reading.
>
> Best regards,
>
> Dalyoung
>
> \usemodule[animation]
> \setupinteraction[state=start]
>
> \startMPdefinitions%{Cardioid}
> path p,q;
> numeric u, ang,j,num;
> picture pict;
>
> u := 1cm;
> ang := 360/52;
>
> p := fullcircle scaled 5u;
> for i=0 upto 51:
> z[i] = 2.5*dir(ang*i)*u;
> endfor;
> pict := image (
> draw p withpen pencircle scaled 1;
> );
> \stopMPdefinitions
>
>
> \startbuffer[Cardioid][s]
> draw pict;
> num := \MPrawvar{Cardioid}{s};
>
> for i = 0 upto num:
> j := 2i mod 52;
> draw z[i] -- z[j];
> endfor;
> setbounds currentpicture to boundingbox currentpicture enlarged 2mm ;
> \stopbuffer
>
> \startdocument
>
> \startanimation[menu=yes, framerate=7]
> \dorecurse{52}
> {\startexpanded
> \startframe
> \setupMPvariables[Cardioid][s=\recurselevel]
> \processMPbuffer[Cardioid]
> \stopframe
> \stopexpanded}
> \stopanimation
> \stopdocument
I don't have the animation module, so maybe I miss the point, but the
code below at least compiles and gives something that could be what
you are looking for. If not, sorry for the noise.
% \usemodule[animation]
\setupinteraction[state=start]
\startMPinitializations% CHANGED
path p,q;
numeric u, ang,j,num;
picture pict;
u := 1cm;
ang := 360/52;
p := fullcircle scaled 5u;
for i=0 upto 51:
z[i] = 2.5*dir(ang*i)*u;
endfor;
z[52]=z[0] ; % NEW
pict := image (
draw p withpen pencircle scaled 1;
);
\stopMPinitializations% CHANGED
\startbuffer[Cardioid][s]
draw pict;
num := \MPrawvar{Cardioid}{s};
for i = 0 upto num:
j := 2i mod 52;
draw z[i] -- z[j];
endfor;
setbounds currentpicture to boundingbox currentpicture enlarged 2mm ;
\stopbuffer
\startdocument
% \startanimation[menu=yes, framerate=7]
\dorecurse{52}
{%\startexpanded
\startframed
\setupMPvariables[Cardioid][s=\recurselevel]
\processMPbuffer[Cardioid]
\stopframed
%\stopexpanded
}
% \stopanimation
\stopdocument
/Mikael
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