minetest/src/light.cpp
Auke Kok 094a5a73d3 Redo light.cpp.
Remake the light_decode_table.

The table starts out without pre-filled in values since those
are always discarded by the code apparently. We calculate a
pseudo curve with gamma power function, and then apply a new
adjustment table.

The adjustment table is setup to make the default gamma of 2.2
look decent: not too dark at light level 3 or so, but too dark
at 1 and below to be playable. The curve is much smoother than
before and looks reasonable at the whole range, offering a
pleasant decay of light levels away from lights.

The `display_gamma` setting now actually does something logical:
the game is darker at values below 2.2, and brighter at values
above 2.2. At 3.0, the game is very bright, but still has a good
light scale. At 1.1 or so, the bottom 5 light levels are virtually
black, but you can still see enough detail at light levels 7-8,
so the range and spread is adequate.

I must add that my monitor is somewhat dark to begin with, since
I have a `hc` screen that doesn't dynamic range colors or try to
pull up `black` pixels for me (it is tuned for accurate color and
light levels), so this should look even better on more dynamic
display tunings.
2016-12-28 14:16:39 -08:00

86 lines
2.5 KiB
C++

/*
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 <math.h>
#include "util/numeric.h"
#ifndef SERVER
// Length of LIGHT_MAX+1 means LIGHT_MAX is the last value.
// LIGHT_SUN is read as LIGHT_MAX from here.
u8 light_LUT[LIGHT_MAX+1];
// the const ref to light_LUT is what is actually used in the code.
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;
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])
light_LUT[i] = light_LUT[i - 1] + 1;
brightness += brightness_step;
}
light_LUT[LIGHT_MAX] = 255;
}
#endif