3 Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU Lesser General Public License as published by
7 the Free Software Foundation; either version 2.1 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public License along
16 with this program; if not, write to the Free Software Foundation, Inc.,
17 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
22 #include "util/numeric.h"
27 static u8 light_LUT[LIGHT_SUN + 1];
29 // The const ref to light_LUT is what is actually used in the code
30 const u8 *light_decode_table = light_LUT;
32 struct LightingParams {
33 float a, b, c; // polynomial coefficients
34 float boost, center, sigma; // normal boost parameters
38 static LightingParams params;
40 float decode_light_f(float x)
42 if (x >= 1.0f) // x is equal to 1.0f half the time
44 x = std::fmax(x, 0.0f);
45 float brightness = ((params.a * x + params.b) * x + params.c) * x;
46 brightness += params.boost * std::exp(-0.5f * sqr((x - params.center) / params.sigma));
47 if (brightness <= 0.0f) // may happen if parameters are insane
49 if (brightness >= 1.0f)
51 return powf(brightness, 1.0f / params.gamma);
54 // Initialize or update the light value tables using the specified gamma
55 void set_light_table(float gamma)
57 // Lighting curve derivatives
58 const float alpha = g_settings->getFloat("lighting_alpha");
59 const float beta = g_settings->getFloat("lighting_beta");
60 // Lighting curve coefficients
61 params.a = alpha + beta - 2.0f;
62 params.b = 3.0f - 2.0f * alpha - beta;
65 params.boost = g_settings->getFloat("lighting_boost");
66 params.center = g_settings->getFloat("lighting_boost_center");
67 params.sigma = g_settings->getFloat("lighting_boost_spread");
69 params.gamma = rangelim(gamma, 0.5f, 3.0f);
71 // Boundary values should be fixed
73 light_LUT[LIGHT_SUN] = 255;
75 for (size_t i = 1; i < LIGHT_SUN; i++) {
76 float brightness = decode_light_f((float)i / LIGHT_SUN);
77 // Strictly speaking, rangelim is not necessary here—if the implementation
78 // is conforming. But we don’t want problems in any case.
79 light_LUT[i] = rangelim((s32)(255.0f * brightness), 0, 255);
80 // Ensure light brightens with each level
81 if (i > 1 && light_LUT[i] <= light_LUT[i - 1])
82 light_LUT[i] = light_LUT[i - 1] + 1;