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New lighting curve (#5279)

* New lighting curve

* Make polynomial lighting curve

* Update default lighting settings
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numberZero authored and nerzhul committed Aug 16, 2017
1 parent 1d8d010 commit 9c8fec83af2c94791865cd82ee18abdc54f913a1
Showing with 34 additions and 44 deletions.
  1. +5 −1 builtin/settingtypes.txt
  2. +8 −2 minetest.conf.example
  3. +3 −1 src/defaultsettings.cpp
  4. +16 −40 src/light.cpp
  5. +2 −0 src/settings_translation_file.cpp
@@ -602,7 +602,11 @@ zoom_fov (Field of view for zoom) int 15 7 160

# Adjust the gamma encoding for the light tables. Higher numbers are brighter.
# This setting is for the client only and is ignored by the server.
display_gamma (Gamma) float 2.2 1.0 3.0
display_gamma (Gamma) float 1.0 0.5 3.0

lighting_alpha (Darkness sharpness) float 0.0 0.0 4.0

lighting_beta (Lightness sharpness) float 0.0 0.0 4.0

# Path to texture directory. All textures are first searched from here.
texture_path (Texture path) path
@@ -702,8 +702,14 @@

# Adjust the gamma encoding for the light tables. Higher numbers are brighter.
# This setting is for the client only and is ignored by the server.
# type: float min: 1 max: 3
# display_gamma = 2.2
# type: float min: 0.5 max: 3.0
# display_gamma = 1.0

# type: float min: 0.0 max: 4.0
# lighting_alpha = 0.0

# type: float min: 0.0 max: 4.0
# lighting_beta = 0.0

# Path to texture directory. All textures are first searched from here.
# type: path
@@ -168,7 +168,9 @@ void set_default_settings(Settings *settings)
settings->setDefault("leaves_style", "fancy");
settings->setDefault("connected_glass", "false");
settings->setDefault("smooth_lighting", "true");
settings->setDefault("display_gamma", "2.2");
settings->setDefault("lighting_alpha", "0.0");
settings->setDefault("lighting_beta", "0.0");
settings->setDefault("display_gamma", "1.0");
settings->setDefault("texture_path", "");
settings->setDefault("shader_path", "");
settings->setDefault("video_driver", "opengl");
@@ -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;
}
@@ -245,6 +245,8 @@ fake_function() {
gettext("Field of view while zooming in degrees.\nThis requires the \"zoom\" privilege on the server.");
gettext("Gamma");
gettext("Adjust the gamma encoding for the light tables. Higher numbers are brighter.\nThis setting is for the client only and is ignored by the server.");
gettext("Darkness sharpness");
gettext("Lightness sharpness");
gettext("Texture path");
gettext("Path to texture directory. All textures are first searched from here.");
gettext("Video driver");

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