/* -*-ePiX-*- */
#include "epix.h"
using namespace ePiX;

// surface to plot (a dog saddle)
P f(double u, double v)
{
  return P(u, v, 0.5*u*v*(u-v)*(u+v));
}

// position-dependent color function
P color(double x, double y, double z)
{
#ifdef LAUREL_BURCH
  return P(-Sin(0.25*x), 0.2, -Cos(0.25*x)); // Laurel Burch colors
#else
  return P(-tanh(z), 0, tanh(z)); // Quasi-geographic 70s colors
#endif
}

int main()
{
  picture(P(-3,-3), P(3,3), "6x6in");

  begin();

  // Set creation attributes,
  revolutions();
  set_crop();
  fill();

  // style attributes,
  backing(Black());
  plain(Yellow());

  // and viewpoint.
  camera.at(P(8, -8, 4));

  // Add scenery
  domain R(P(-2,-2), P(2, 2), mesh(36, 36), mesh(72, 72));
  surface(f, R, color);

  // and print
  pst_format();
  end();
}