Rotation of a 3D contour

animation 84K

kp=xget("pixmap");xset("pixmap",1);
xset("wwpc");
t=-%pi:0.3:%pi;
contour(t,t,sin(t)'*cos(t),10,35,45,"X@Y@Z",[0,2,4])
xset("wshow");
if driver()=='Pos' then sp=5; else sp=1;end
for i=35:sp:80,
  xset("wwpc");
  contour(t,t,sin(t)'*cos(t),10,i,45,"X@Y@Z",[0,0,4])
  xset("wshow");
end
for i=45:sp:80,
  xset("wwpc");
  contour(t,t,sin(t)'*cos(t),10,80,i,"X@Y@Z",[0,0,4])
  xset("wshow");
end
xset("pixmap",kp);