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- /*
- Minetest
- Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
- (at your option) any later version.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU Lesser General Public License for more details.
- You should have received a copy of the GNU Lesser General Public License along
- with this program; if not, write to the Free Software Foundation, Inc.,
- 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- */
- #include "light.h"
- #include <cmath>
- #include "util/numeric.h"
- #include "settings.h"
- #ifndef SERVER
- static u8 light_LUT[LIGHT_SUN + 1];
- // The const ref to light_LUT is what is actually used in the code
- const u8 *light_decode_table = light_LUT;
- // Initialize or update the light value tables using the specified gamma
- void set_light_table(float gamma)
- {
- // Lighting curve derivatives
- const float alpha = g_settings->getFloat("lighting_alpha");
- const float beta = g_settings->getFloat("lighting_beta");
- // Lighting curve coefficients
- const float a = alpha + beta - 2.0f;
- const float b = 3.0f - 2.0f * alpha - beta;
- const float c = alpha;
- // Mid boost
- const float d = g_settings->getFloat("lighting_boost");
- const float e = g_settings->getFloat("lighting_boost_center");
- const float f = g_settings->getFloat("lighting_boost_spread");
- // Gamma correction
- gamma = rangelim(gamma, 0.5f, 3.0f);
- for (size_t i = 0; i < LIGHT_SUN; i++) {
- float x = i;
- x /= LIGHT_SUN;
- float brightness = a * x * x * x + b * x * x + c * x;
- float boost = d * std::exp(-((x - e) * (x - e)) / (2.0f * f * f));
- brightness = powf(brightness + boost, 1.0f / gamma);
- light_LUT[i] = rangelim((u32)(255.0f * brightness), 0, 255);
- if (i > 1 && light_LUT[i] <= light_LUT[i - 1])
- light_LUT[i] = light_LUT[i - 1] + 1;
- }
- light_LUT[LIGHT_SUN] = 255;
- }
- #endif
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