update packages

[CreaPhase.git] / octave_packages / m / plot / specular.m

diff --git a/octave_packages/m/plot/specular.m b/octave_packages/m/plot/specular.m
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+## Copyright (C) 2009-2012 Kai Habel
+##
+## 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} {} specular (@var{sx}, @var{sy}, @var{sz}, @var{lv}, @var{vv})
+## @deftypefnx {Function File} {} specular (@var{sx}, @var{sy}, @var{sz}, @var{lv}, @var{vv}, @var{se})
+## Calculate specular reflection strength of a surface defined by the normal
+## vector elements @var{sx}, @var{sy}, @var{sz} using Phong's approximation.
+## The light and view vectors can be specified using parameter @var{lv} and
+## @var{vv} respectively.
+## Both can be given as 2-element vectors [azimuth, elevation] in degrees or as
+## 3-element
+## vector [x, y, z].  An optional 6th argument describes the specular exponent
+## (spread) @var{se}.
+## @seealso{surfl, diffuse}
+## @end deftypefn
+
+## Author: Kai Habel <kai.habel@gmx.de>
+
+function retval = specular (sx, sy, sz, lv, vv, se)
+
+  if (nargin < 5 || nargin > 6)
+    print_usage ();
+  endif
+
+  ## Checks for specular exponent (se).
+  if (nargin < 6)
+    se = 10;
+  else
+    if (!isnumeric (se) || numel (se) != 1 || se <= 0)
+      error ("specular: exponent must be positive scalar");
+    endif
+  endif
+
+  ## Checks for normal vector.
+  if (!size_equal (sx, sy, sz))
+    error ("specular: SX, SY, and SZ must have same size");
+  endif
+
+  ## Check for light vector (lv) argument.
+  if (length (lv) < 2 || length (lv) > 3)
+    error ("specular: light vector LV must be a 2- or 3-element vector");
+  elseif (length (lv) == 2)
+    [lv(1), lv(2), lv(3)] = sph2cart (lv(1) * pi/180, lv(2) * pi/180, 1.0);
+  endif
+
+  ## Check for view vector (vv) argument.
+  if (length (vv) < 2 || length (lv) > 3)
+    error ("specular: view vector VV must be a 2- or 3-element vector");
+  elseif (length (vv) == 2)
+    [vv(1), vv(2), vv(3)] = sph2cart (vv(1) * pi / 180, vv(2) * pi / 180, 1.0);
+  endif
+
+  ## Normalize view and light vector.
+  if (sum (abs (lv)) > 0)
+    lv  /= norm (lv);
+  endif
+  if (sum (abs (vv)) > 0)
+    vv  /= norm (vv);
+  endif
+
+  ## Calculate normal vector lengths and dot-products.
+  ns = sqrt (sx.^2 + sy.^2 + sz.^2);
+  l_dot_n = (sx * lv(1) + sy * lv(2) + sz * lv(3)) ./ ns;
+  v_dot_n = (sx * vv(1) + sy * vv(2) + sz * vv(3)) ./ ns;
+
+  ## Calculate specular reflection using Phong's approximation.
+  retval = 2 * l_dot_n .* v_dot_n - dot (lv, vv);
+
+  ## Set zero if light is on the other side.
+  retval(l_dot_n < 0) = 0;
+
+  ## Allow postive values only.
+  retval(retval < 0) = 0;
+  retval = retval .^ se;
+
+endfunction