// create a 3rd order infinite polynomial surface
cubic {
  <
// x^3,      x^2y,     x^2z,     x^2,
   1,        0,        0,        0,
// xy^2,     xyz,      xy,       xz^2,
   0,        1,        0,        0,
// xz,       x,        y^3,      y^2z,
   0,        0,        1,        0,
// y^2,      yz^2,     yz,       y,
   0,        0,        0,        1,
// z^3,      z^2,      z,        C
   0,        0,        0,        1
  >
 // sturm // optional, slower but reduces speckles
}

