1 ## Copyright (C) 2009-2012 Kai Habel
3 ## This file is part of Octave.
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20 ## @deftypefn {Function File} {} specular (@var{sx}, @var{sy}, @var{sz}, @var{lv}, @var{vv})
21 ## @deftypefnx {Function File} {} specular (@var{sx}, @var{sy}, @var{sz}, @var{lv}, @var{vv}, @var{se})
22 ## Calculate specular reflection strength of a surface defined by the normal
23 ## vector elements @var{sx}, @var{sy}, @var{sz} using Phong's approximation.
24 ## The light and view vectors can be specified using parameter @var{lv} and
25 ## @var{vv} respectively.
26 ## Both can be given as 2-element vectors [azimuth, elevation] in degrees or as
28 ## vector [x, y, z]. An optional 6th argument describes the specular exponent
30 ## @seealso{surfl, diffuse}
33 ## Author: Kai Habel <kai.habel@gmx.de>
35 function retval = specular (sx, sy, sz, lv, vv, se)
37 if (nargin < 5 || nargin > 6)
41 ## Checks for specular exponent (se).
45 if (!isnumeric (se) || numel (se) != 1 || se <= 0)
46 error ("specular: exponent must be positive scalar");
50 ## Checks for normal vector.
51 if (!size_equal (sx, sy, sz))
52 error ("specular: SX, SY, and SZ must have same size");
55 ## Check for light vector (lv) argument.
56 if (length (lv) < 2 || length (lv) > 3)
57 error ("specular: light vector LV must be a 2- or 3-element vector");
58 elseif (length (lv) == 2)
59 [lv(1), lv(2), lv(3)] = sph2cart (lv(1) * pi/180, lv(2) * pi/180, 1.0);
62 ## Check for view vector (vv) argument.
63 if (length (vv) < 2 || length (lv) > 3)
64 error ("specular: view vector VV must be a 2- or 3-element vector");
65 elseif (length (vv) == 2)
66 [vv(1), vv(2), vv(3)] = sph2cart (vv(1) * pi / 180, vv(2) * pi / 180, 1.0);
69 ## Normalize view and light vector.
70 if (sum (abs (lv)) > 0)
73 if (sum (abs (vv)) > 0)
77 ## Calculate normal vector lengths and dot-products.
78 ns = sqrt (sx.^2 + sy.^2 + sz.^2);
79 l_dot_n = (sx * lv(1) + sy * lv(2) + sz * lv(3)) ./ ns;
80 v_dot_n = (sx * vv(1) + sy * vv(2) + sz * vv(3)) ./ ns;
82 ## Calculate specular reflection using Phong's approximation.
83 retval = 2 * l_dot_n .* v_dot_n - dot (lv, vv);
85 ## Set zero if light is on the other side.
86 retval(l_dot_n < 0) = 0;
88 ## Allow postive values only.
89 retval(retval < 0) = 0;
90 retval = retval .^ se;