3 Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU Lesser General Public License as published by
7 the Free Software Foundation; either version 2.1 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public License along
16 with this program; if not, write to the Free Software Foundation, Inc.,
17 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
22 #include "util/numeric.h"
26 // Length of LIGHT_MAX+1 means LIGHT_MAX is the last value.
27 // LIGHT_SUN is read as LIGHT_MAX from here.
29 u8 light_LUT[LIGHT_MAX+1];
31 // the const ref to light_LUT is what is actually used in the code.
32 const u8 *light_decode_table = light_LUT;
34 /** Initialize or update the light value tables using the specified \p gamma.
35 * If \p gamma == 1.0 then the light table is linear. Typically values for
36 * gamma range between 1.8 and 2.2.
38 * @note The value for gamma will be restricted to the range 1.1 <= gamma <= 3.0.
40 * @note This function is not, currently, a simple linear to gamma encoding
41 * because adjustments are made so that a gamma of 1.8 gives the same
42 * results as those hardcoded for use by the server.
44 void set_light_table(float gamma)
46 static const float brightness_step = 255.0f / (LIGHT_MAX + 1);
48 // this table is pure arbitrary values, made so that
49 // at gamma 2.2 the game looks not too dark at light=1,
50 // and mostly linear for the rest of the scale.
51 // we could try to inverse the gamma power function, but this
52 // is simpler and quicker.
53 static const int adjustments[LIGHT_MAX + 1] = {
71 gamma = rangelim(gamma, 1.0, 3.0);
73 float brightness = brightness_step;
75 for (size_t i = 0; i < LIGHT_MAX; i++) {
76 light_LUT[i] = (u8)(255 * powf(brightness / 255.0f, 1.0 / gamma));
77 light_LUT[i] = rangelim(light_LUT[i] + adjustments[i], 0, 255);
78 if (i > 1 && light_LUT[i] < light_LUT[i - 1])
79 light_LUT[i] = light_LUT[i - 1] + 1;
80 brightness += brightness_step;
82 light_LUT[LIGHT_MAX] = 255;