plot3d (cos(-x^2 + y^3/4), [x,-4,4], [y,-4,4], [zlabel,""],
  nomesh_lines, [elevation,0], [azimuth,0], color_bar,
  [grid,80,80], noztics, [color_bar_tics,1], [pdf_file,"./plotting26.pdf"]);
plot3d (cos(-x^2 + y^3/4), [x,-4,4], [y,-4,4], [zlabel,""],
  nomesh_lines, [elevation,0], [azimuth,0], color_bar,
  [grid,80,80], noztics, [color_bar_tics,1], [png_file,"./plotting26.png"]);
