mirror of https://github.com/minetest/minetest.git
86 lines
2.5 KiB
C++
86 lines
2.5 KiB
C++
/*
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Minetest
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Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License along
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with this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "light.h"
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#include <math.h>
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#include "util/numeric.h"
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#ifndef SERVER
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// Length of LIGHT_MAX+1 means LIGHT_MAX is the last value.
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// LIGHT_SUN is read as LIGHT_MAX from here.
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u8 light_LUT[LIGHT_MAX+1];
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// the const ref to light_LUT is what is actually used in the code.
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const u8 *light_decode_table = light_LUT;
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/** Initialize or update the light value tables using the specified \p gamma.
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* If \p gamma == 1.0 then the light table is linear. Typically values for
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* gamma range between 1.8 and 2.2.
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*
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* @note The value for gamma will be restricted to the range 1.1 <= gamma <= 3.0.
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*
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* @note This function is not, currently, a simple linear to gamma encoding
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* because adjustments are made so that a gamma of 1.8 gives the same
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* results as those hardcoded for use by the server.
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*/
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void set_light_table(float gamma)
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{
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static const float brightness_step = 255.0f / (LIGHT_MAX + 1);
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// this table is pure arbitrary values, made so that
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// at gamma 2.2 the game looks not too dark at light=1,
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// and mostly linear for the rest of the scale.
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// we could try to inverse the gamma power function, but this
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// is simpler and quicker.
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static const int adjustments[LIGHT_MAX + 1] = {
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-67,
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-91,
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-125,
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-115,
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-104,
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-85,
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-70,
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-63,
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-56,
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-49,
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-42,
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-35,
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-28,
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-22,
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0
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};
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gamma = rangelim(gamma, 1.0, 3.0);
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float brightness = brightness_step;
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for (size_t i = 0; i < LIGHT_MAX; i++) {
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light_LUT[i] = (u8)(255 * powf(brightness / 255.0f, 1.0 / gamma));
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light_LUT[i] = rangelim(light_LUT[i] + adjustments[i], 0, 255);
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if (i > 1 && light_LUT[i] < light_LUT[i - 1])
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light_LUT[i] = light_LUT[i - 1] + 1;
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brightness += brightness_step;
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}
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light_LUT[LIGHT_MAX] = 255;
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}
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#endif
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