123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293 |
- /*
- 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 <algorithm>
- #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;
- 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
|