## Copyright (C) 1996, 1997, 2007 John W. Eaton
##
## This file is part of Octave.
##
## Octave is free software; you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 3 of the License, or (at
## your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
## General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, see
## <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {} surfc (@var{x}, @var{y}, @var{z})
## Plot a surface and contour given matrices @var{x}, and @var{y} from 
## @code{meshgrid} and a matrix @var{z} corresponding to the @var{x} and 
## @var{y} coordinates of the mesh.  If @var{x} and @var{y} are vectors, 
## then a typical vertex is (@var{x}(j), @var{y}(i), @var{z}(i,j)).  Thus, 
## columns of @var{z} correspond to different @var{x} values and rows of 
## @var{z} correspond to different @var{y} values.
## @seealso{meshgrid, surf, contour}
## @end deftypefn

function h = surfc (varargin)

  newplot ();

  tmp = surface (varargin{:});

  ax = get (tmp, "parent");

  set (tmp, "facecolor", "flat");

  if (! ishold ())
    set (ax, "view", [-37.5, 30]);
  endif

  hold ("on");

  [c, lev] = contourc (varargin{:});

  cmap = get (gcf(), "colormap");
  
  levx = linspace (min (lev), max (lev), size (cmap, 1));

  drawnow ();
  ax = axis ();
  zmin = 2 * ax(5) - ax(6);

  ## decode contourc output format
  i1 = 1;
  while (i1 < length (c))

    clev = c(1,i1);
    clen = c(2,i1);

    ccr = interp1 (levx, cmap(:,1), clev);
    ccg = interp1 (levx, cmap(:,2), clev);
    ccb = interp1 (levx, cmap(:,3), clev);

    ii = i1+1:i1+clen;
    line (c(1,ii), c(2,ii), zmin*ones(size(ii)), "color", [ccr, ccg, ccb]);

    i1 += c(2,i1)+1;
  endwhile
  
  if (nargout > 0)
    h = tmp;
  endif

endfunction