/* Minetest Copyright (C) 2013 celeron55, Perttu Ahola 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 #include #include "util/numeric.h" #include "settings.h" #if CHECK_CLIENT_BUILD() 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; struct LightingParams { float a, b, c; // Lighting curve polynomial coefficients float boost, center, sigma; // Lighting curve parametric boost float gamma; // Lighting curve gamma correction }; static LightingParams params; float decode_light_f(float x) { if (x >= 1.0f) // x is often 1.0f return 1.0f; x = std::fmax(x, 0.0f); float brightness = ((params.a * x + params.b) * x + params.c) * x; brightness += params.boost * std::exp(-0.5f * sqr((x - params.center) / params.sigma)); if (brightness <= 0.0f) // May happen if parameters are extreme return 0.0f; if (brightness >= 1.0f) return 1.0f; return powf(brightness, 1.0f / params.gamma); } // Initialize or update the light value tables using the specified gamma void set_light_table(float gamma) { // Lighting curve bounding gradients const float alpha = rangelim(g_settings->getFloat("lighting_alpha"), 0.0f, 3.0f); const float beta = rangelim(g_settings->getFloat("lighting_beta"), 0.0f, 3.0f); // Lighting curve polynomial coefficients params.a = alpha + beta - 2.0f; params.b = 3.0f - 2.0f * alpha - beta; params.c = alpha; // Lighting curve parametric boost params.boost = rangelim(g_settings->getFloat("lighting_boost"), 0.0f, 0.4f); params.center = rangelim(g_settings->getFloat("lighting_boost_center"), 0.0f, 1.0f); params.sigma = rangelim(g_settings->getFloat("lighting_boost_spread"), 0.0f, 0.4f); // Lighting curve gamma correction params.gamma = rangelim(gamma, 0.33f, 3.0f); // Boundary values should be fixed light_LUT[0] = 0; light_LUT[LIGHT_SUN] = 255; for (size_t i = 1; i < LIGHT_SUN; i++) { float brightness = decode_light_f((float)i / LIGHT_SUN); // Strictly speaking, rangelim is not necessary here—if the implementation // is conforming. But we don’t want problems in any case. light_LUT[i] = rangelim((s32)(255.0f * brightness), 0, 255); // Ensure light brightens with each level if (i > 0 && light_LUT[i] <= light_LUT[i - 1]) { light_LUT[i] = std::min((u8)254, light_LUT[i - 1]) + 1; } } } #endif