1 ## Copyright (C) 2009-2012 Kai Habel
3 ## This file is part of Octave.
5 ## Octave is free software; you can redistribute it and/or modify it
6 ## under the terms of the GNU General Public License as published by
7 ## the Free Software Foundation; either version 3 of the License, or (at
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13 ## General Public License for more details.
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20 ## @deftypefn {Function File} {} diffuse (@var{sx}, @var{sy}, @var{sz}, @var{lv})
21 ## Calculate diffuse reflection strength of a surface defined by the normal
22 ## vector elements @var{sx}, @var{sy}, @var{sz}.
23 ## The light vector can be specified using parameter @var{lv}. It can be
24 ## given as 2-element vector [azimuth, elevation] in degrees or as 3-element
25 ## vector [lx, ly, lz].
26 ## @seealso{specular, surfl}
29 ## Author: Kai Habel <kai.habel@gmx.de>
31 function retval = diffuse (sx, sy, sz, lv)
37 ## check for normal vector
38 if (!size_equal (sx, sy, sz))
39 error ("diffuse: SX, SY, and SZ must have same size");
42 ## check for light vector (lv) argument
43 if (length (lv) < 2 || length (lv) > 3)
44 error ("diffuse: light vector LV must be a 2- or 3-element vector");
45 elseif (length (lv) == 2)
46 [lv(1), lv(2), lv(3)] = sph2cart (lv(1) * pi/180, lv(2) * pi/180, 1.0);
49 ## Normalize view and light vector.
50 if (sum (abs (lv)) > 0)
54 ns = sqrt (sx.^2 + sy.^2 + sz.^2);
55 retval = (sx * lv(1) + sy * lv(2) + sz * lv(3)) ./ ns;
56 retval(retval < 0) = 0;