Hyperboloid

      u =  ((Grid.xBounds[1] - Grid.xBounds[0]) * (s-0.5)) * M_PI;
      v =  ((Grid.xBounds[1] - Grid.xBounds[0]) * (t-0.5) + 1) * M_PI;
      a = 0.5;  // less makes it taller, more makes it shorter
      c = 0.4;  // less makes it wider, more makes it narrower

      x = a*sqrt(1+u*u)*cos(v);
      y = a*sqrt(1+u*u)*sin(v);
      z = c*u;

a=0.8, c=0.8	a=0.5, c=0.8	a=0.5, c=0.4

Helicoid

      u =  ((Grid.xBounds[1] - Grid.xBounds[0]) * (s-0.5)) * M_PI;
      v =  ((Grid.xBounds[1] - Grid.xBounds[0]) * (t-0.5)) * M_PI;
      c = 0.7;  // less makes it flatter, more stretches it out

      x = u*cos(v);
      y = u*sin(v);
      z = c*v;

c=0.3	c=0.7

Cornucopia

      u =  ((Grid.xBounds[1] - Grid.xBounds[0]) * (s-0.5)) * M_PI;
      v =  ((Grid.xBounds[1] - Grid.xBounds[0]) * (t-0.5)) * M_PI;
      a = 0.7;  // less makes it longer, more makes it shorter
      b = 0.5;  // less makes it fold in on itself, more unrolls it

      x = exp(b*v)*cos(v)+exp(a*v)*cos(u)*cos(v);
      y = exp(b*v)*sin(v)+exp(a*v)*cos(u)*sin(v);
      z = exp(a*v)*sin(u);

a=0.7, b=0.9	a=0.9, b=0.9	a=0.7, b=0.5