-#include "light.h"
-
/*
+Minetest
+Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
-#!/usr/bin/python
+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.
-from math import *
-from sys import stdout
+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.
-# We want 0 at light=0 and 255 at light=LIGHT_MAX
-LIGHT_MAX = 15
+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.
+*/
-L = []
-for i in range(1,LIGHT_MAX+1):
- L.append(int(round(255.0 * 0.69 ** (i-1))))
- L.append(0)
+#include "light.h"
+#include <cmath>
+#include "util/numeric.h"
+#include "settings.h"
-L.reverse()
-for i in L:
- stdout.write(str(i)+",\n")
+#ifndef SERVER
-*/
+static u8 light_LUT[LIGHT_SUN + 1];
-/*
- The first value should be 0, the last value should be 255.
-*/
-/*u8 light_decode_table[LIGHT_MAX+1] =
-{
-0,
-2,
-3,
-4,
-6,
-9,
-13,
-19,
-28,
-40,
-58,
-84,
-121,
-176,
-255,
-};*/
+// The const ref to light_LUT is what is actually used in the code
+const u8 *light_decode_table = light_LUT;
-/*
-#!/usr/bin/python
-from math import *
-from sys import stdout
+struct LightingParams {
+ float a, b, c; // Lighting curve polynomial coefficients
+ float boost, center, sigma; // Lighting curve parametric boost
+ float gamma; // Lighting curve gamma correction
+};
-# We want 0 at light=0 and 255 at light=LIGHT_MAX
-LIGHT_MAX = 14
-#FACTOR = 0.69
-FACTOR = 0.75
+static LightingParams params;
-L = []
-for i in range(1,LIGHT_MAX+1):
- L.append(int(round(255.0 * FACTOR ** (i-1))))
-L.append(0)
-L.reverse()
-for i in L:
- stdout.write(str(i)+",\n")
-*/
-u8 light_decode_table[LIGHT_MAX+1] =
+float decode_light_f(float x)
{
-0,
-6,
-8,
-11,
-14,
-19,
-26,
-34,
-45,
-61,
-81,
-108,
-143,
-191,
-255,
-};
+ 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 > 1 && light_LUT[i] <= light_LUT[i - 1])
+ light_LUT[i] = light_LUT[i - 1] + 1;
+ }
+}
+#endif