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