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########################################################################
##
## Copyright (C) 2009-2024 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## 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
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {} surfl (@var{z})
## @deftypefnx {} {} surfl (@var{x}, @var{y}, @var{z})
## @deftypefnx {} {} surfl (@dots{}, @var{lsrc})
## @deftypefnx {} {} surfl (@var{x}, @var{y}, @var{z}, @var{lsrc}, @var{P})
## @deftypefnx {} {} surfl (@dots{}, "cdata")
## @deftypefnx {} {} surfl (@dots{}, "light")
## @deftypefnx {} {} surfl (@var{hax}, @dots{})
## @deftypefnx {} {@var{h} =} surfl (@dots{})
## Plot a 3-D surface using shading based on various lighting models.
##
## The surface mesh is plotted using shaded rectangles. The vertices of the
## rectangles [@var{x}, @var{y}] are typically the output of @code{meshgrid}.
## over a 2-D rectangular region in the x-y plane. @var{z} determines the
## height above the plane of each vertex. If only a single @var{z} matrix is
## given, then it is plotted over the meshgrid
## @code{@var{x} = 1:columns (@var{z}), @var{y} = 1:rows (@var{z})}.
## Thus, columns of @var{z} correspond to different @var{x} values and rows
## of @var{z} correspond to different @var{y} values.
##
## The default lighting mode @qcode{"cdata"}, changes the cdata property of the
## surface object to give the impression of a lighted surface.
##
## The alternate mode @qcode{"light"} creates a light object to illuminate the
## surface.
##
## The light source location may be specified using @var{lsrc} which can be
## a 2-element vector [azimuth, elevation] in degrees, or a 3-element vector
## [lx, ly, lz]. The default value is rotated 45 degrees counterclockwise to
## the current view.
##
## The material properties of the surface can specified using a 4-element
## vector @var{P} = [@var{AM} @var{D} @var{SP} @var{exp}] which defaults to
## @var{p} = [0.55 0.6 0.4 10].
##
## @table @asis
## @item @qcode{"AM"} strength of ambient light
##
## @item @qcode{"D"} strength of diffuse reflection
##
## @item @qcode{"SP"} strength of specular reflection
##
## @item @qcode{"EXP"} specular exponent
## @end table
##
## If the first argument @var{hax} is an axes handle, then plot into this axes,
## rather than the current axes returned by @code{gca}.
##
## The optional return value @var{h} is a graphics handle to the created
## surface object.
##
## Example:
##
## @example
## @group
## colormap (bone (64));
## surfl (peaks);
## shading interp;
## @end group
## @end example
## @seealso{diffuse, specular, surf, shading, colormap, caxis}
## @end deftypefn
function h = surfl (varargin)
[hax, varargin, nargin] = __plt_get_axis_arg__ ("surfl", varargin{:});
if (nargin == 0)
print_usage ();
endif
## Check for lighting type.
use_cdata = true;
if (ischar (varargin{end}))
switch (lower (varargin{end}))
case "light"
use_cdata = false;
case "cdata"
use_cdata = true;
otherwise
error ("surfl: unknown lighting method");
endswitch
varargin(end) = [];
endif
## Check for reflection properties argument.
##
## r = [ambient light strength,
## diffuse reflection strength,
## specular reflection strength,
## specular shine]
if (isnumeric (varargin{end}) && isvector (varargin{end})
&& (numel (varargin{end}) == 4))
r = varargin{end};
varargin(end) = [];
else
## Default values.
r = [0.55, 0.6, 0.4, 10];
endif
## Check for light vector (lv) argument.
have_lv = false;
if (isnumeric (varargin{end}) && isvector (varargin{end}))
len = numel (varargin{end});
lastarg = varargin{end};
if (len == 3)
lv = lastarg;
varargin(end) = [];
have_lv = true;
elseif (len == 2)
[lv(1), lv(2), lv(3)] = sph2cart ((lastarg(1) - 90) * pi/180,
lastarg(2) * pi/180,
1.0);
varargin(end) = [];
have_lv = true;
endif
endif
oldfig = [];
if (! isempty (hax))
oldfig = get (0, "currentfigure");
endif
unwind_protect
hax = newplot (hax);
htmp = surface (varargin{:});
if (! ishold ())
set (hax, "view", [-37.5, 30],
"xgrid", "on", "ygrid", "on", "zgrid", "on");
endif
## Get view vector (vv).
[az, el] = view ();
[vv(1), vv(2), vv(3)] = sph2cart ((az - 90) * pi/180.0, el * pi/180.0, 1.0);
if (! have_lv)
## Calculate light vector (lv) from view vector.
phi = pi / 4; # 45 degrees
R = [cos(phi), -sin(phi), 0;
sin(phi), cos(phi), 0;
0, 0, 1];
lv = (R * vv.').';
endif
if (use_cdata)
set (hax, "clim", [0 1]);
__update_normals__ (htmp);
vn = get (htmp, "vertexnormals");
dar = get (hax, "dataaspectratio");
vn(:,:,1) *= dar(1);
vn(:,:,2) *= dar(2);
vn(:,:,3) *= dar(3);
## Normalize vn.
vn ./= repmat (sqrt (sumsq (vn, 3)), [1, 1, 3]);
[nr, nc] = size (get (htmp, "zdata"));
## Ambient, diffuse, and specular term.
cdata = ( r(1) * ones (nr, nc)
+ r(2) * diffuse (vn(:,:,1), vn(:,:,2), vn(:,:,3), lv)
+ r(3) * specular (vn(:,:,1), vn(:,:,2), vn(:,:,3), lv, vv, r(4)));
cdata ./= sum (r(1:3));
set (htmp, "cdata", cdata);
else
light (hax, "position", lv);
set (htmp, "ambientstrength", r(1), "diffusestrength", r(2), ...
"specularstrength", r(3), "specularexponent", r(4));
endif
unwind_protect_cleanup
if (! isempty (oldfig))
set (0, "currentfigure", oldfig);
endif
end_unwind_protect
if (nargout > 0)
h = htmp;
endif
endfunction
%!demo
%! clf;
%! [X,Y,Z] = sombrero ();
%! colormap (copper (64));
%! surfl (X,Y,Z);
%! shading interp;
%! title ("surfl() with defaults");
%!demo
%! clf;
%! [X,Y,Z] = sombrero ();
%! colormap (copper (64));
%! surfl (X,Y,Z, [62.50,30], [0.2 0.6 0.4 25]);
%! shading interp;
%! title ("surfl() with lighting vector and material properties");
%!demo
%! clf;
%! [X, Y] = meshgrid (-3:1/8:3);
%! Z = peaks (X, Y);
%! surfl (X, Y, Z, "light");
%! shading interp;
%! title ("surfl() with light object");
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