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comparison scripts/plot/diffuse.m @ 8450:6c4e2fc14beb

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Add new 3D plotting function surfl. Add light functions diffuse and specular
author Kai Habel
date Thu, 08 Jan 2009 15:51:50 +0100
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8449:448188853722 8450:6c4e2fc14beb
1 ## Copyright (C) 2009 Kai Habel
2 ##
3 ## This file is part of Octave.
4 ##
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
8 ## your option) any later version.
9 ##
10 ## Octave is distributed in the hope that it will be useful, but
11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
14 ##
15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, see
17 ## <http://www.gnu.org/licenses/>.
18
19 ## -*- texinfo -*-
20 ## @deftypefn {Function File} {} diffuse (@var{sx}, @var{sy}, @var{sz}, @var{l})
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{L}. 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}
27 ## @end deftypefn
28
29 ## Author: Kai Habel <kai.habel@gmx.de>
30
31 function retval = diffuse (sx, sy, sz, lv)
32
33 ## general checks
34 if (nargin != 4)
35 usage ("number of arguments must be 4")
36 endif
37
38 ## check for normal vector
39 if (!size_equal (sx, sy, sz))
40 usage ("SX, SY, and SZ must have same size")
41 endif
42
43 ## check for light vector (lv) argument
44 if (length (lv) < 2 || length (lv) > 3)
45 usage ("light vector LV must be a 2- or 3-element vector");
46 elseif (length (lv) == 2)
47 [lv(1), lv(2), lv(3)] = sph2cart (lv(1) * pi/180, lv(2) * pi/180, 1.0);
48 endif
49
50 ## normalize view and light vector
51 if (sum (abs (lv)) > 0)
52 lv /= norm (lv);
53 endif
54
55 ns = sqrt (sx.^2 + sy.^2 + sz.^2);
56 retval = (sx * lv(1) + sy * lv(2) + sz * lv(3)) ./ ns;
57 retval(retval < 0) = 0;
58
59 endfunction