mirror of https://github.com/minetest/minetest.git
62 lines
1.9 KiB
C++
62 lines
1.9 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 <cmath>
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#include "util/numeric.h"
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#include "settings.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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*/
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void set_light_table(float gamma)
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{
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// lighting curve derivatives
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const float alpha = g_settings->getFloat("lighting_alpha");
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const float beta = g_settings->getFloat("lighting_beta");
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// lighting curve coefficients
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const float a = alpha + beta - 2;
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const float b = 3 - 2 * alpha - beta;
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const float c = alpha;
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// gamma correction
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gamma = rangelim(gamma, 0.5, 3.0);
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for (size_t i = 0; i < LIGHT_MAX; i++) {
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float x = i;
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x /= LIGHT_MAX;
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float brightness = a * x * x * x + b * x * x + c * x;
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brightness = powf(brightness, 1.0 / gamma);
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light_LUT[i] = rangelim((u32)(255 * brightness), 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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}
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light_LUT[LIGHT_MAX] = 255;
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}
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#endif
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