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New lighting curve (#5279)

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* New lighting curve

* Make polynomial lighting curve

* Update default lighting settings
This commit is contained in:
Vitaliy 2017-08-17 01:23:20 +03:00 • committed by Loïc Blot
parent 1d8d01074f
commit 9c8fec83af
5 changed files with 34 additions and 44 deletions
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56
src/light.cpp
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@ -20,6 +20,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
#include "light.h"
#include <math.h>
#include "util/numeric.h"
#include "settings.h"
#ifndef SERVER
@ -32,52 +33,27 @@ u8 light_LUT[LIGHT_MAX+1];
const u8 *light_decode_table = light_LUT;
/** Initialize or update the light value tables using the specified \p gamma.
* If \p gamma == 1.0 then the light table is linear. Typically values for
* gamma range between 1.8 and 2.2.
*
* @note The value for gamma will be restricted to the range 1.1 <= gamma <= 3.0.
*
* @note This function is not, currently, a simple linear to gamma encoding
* because adjustments are made so that a gamma of 1.8 gives the same
* results as those hardcoded for use by the server.
*/
void set_light_table(float gamma)
{
static const float brightness_step = 255.0f / (LIGHT_MAX + 1);
// this table is pure arbitrary values, made so that
// at gamma 2.2 the game looks not too dark at light=1,
// and mostly linear for the rest of the scale.
// we could try to inverse the gamma power function, but this
// is simpler and quicker.
static const int adjustments[LIGHT_MAX + 1] = {
-67,
-91,
-125,
-115,
-104,
-85,
-70,
-63,
-56,
-49,
-42,
-35,
-28,
-22,
0
};
gamma = rangelim(gamma, 1.0, 3.0);
float brightness = brightness_step;
// 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;
const float b = 3 - 2 * alpha - beta;
const float c = alpha;
// gamma correction
gamma = rangelim(gamma, 0.5, 3.0);
for (size_t i = 0; i < LIGHT_MAX; i++) {
light_LUT[i] = (u8)(255 * powf(brightness / 255.0f, 1.0 / gamma));
light_LUT[i] = rangelim(light_LUT[i] + adjustments[i], 0, 255);
if (i > 1 && light_LUT[i] < light_LUT[i - 1])
float x = i;
x /= LIGHT_MAX;
float brightness = a * x * x * x + b * x * x + c * x;
brightness = powf(brightness, 1.0 / gamma);
light_LUT[i] = rangelim((u32)(255 * brightness), 0, 255);
if (i > 1 && light_LUT[i] <= light_LUT[i - 1])
light_LUT[i] = light_LUT[i - 1] + 1;
brightness += brightness_step;
}
light_LUT[LIGHT_MAX] = 255;
}