[borisp]

http://www.gamate.com/casestudy/supershape/

function Supershape(m,n1,n2,n3,phi,a,b,x,y,env) {
   var r;
   r = POW(POW(ABS(COS(m * phi / 4) / a),n2)+POW(ABS(SIN(m * phi / 4) / b),n3),1/n1);
   if (ABS(r) == 0) {
      env.x = 0;
      env.y = 0;
   } else {
      r = 1 / r;
      env.x = r * COS(phi);
      env.y = r * SIN(phi);
   }
}