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Light curve: Simplify and improve code, fix darkened daytime sky (#7693)

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Vitaliy 2018-09-16 19:59:42 +03:00 • committed by Paramat
parent 220ec79e4a
commit 79e393cf4b
3 changed files with 46 additions and 30 deletions
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55
src/light.cpp
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@ -29,6 +29,28 @@ static u8 light_LUT[LIGHT_SUN + 1];
// The const ref to light_LUT is what is actually used in the code
const u8 *light_decode_table = light_LUT;
struct LightingParams {
float a, b, c; // polynomial coefficients
float boost, center, sigma; // normal boost parameters
float gamma;
};
static LightingParams params;
float decode_light_f(float x)
{
if (x >= 1.0f) // x is equal to 1.0f half the time
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 insane
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)
{
@ -36,26 +58,29 @@ void set_light_table(float gamma)
const float alpha = g_settings->getFloat("lighting_alpha");
const float beta = g_settings->getFloat("lighting_beta");
// Lighting curve coefficients
const float a = alpha + beta - 2.0f;
const float b = 3.0f - 2.0f * alpha - beta;
const float c = alpha;
params.a = alpha + beta - 2.0f;
params.b = 3.0f - 2.0f * alpha - beta;
params.c = alpha;
// Mid boost
const float d = g_settings->getFloat("lighting_boost");
const float e = g_settings->getFloat("lighting_boost_center");
const float f = g_settings->getFloat("lighting_boost_spread");
params.boost = g_settings->getFloat("lighting_boost");
params.center = g_settings->getFloat("lighting_boost_center");
params.sigma = g_settings->getFloat("lighting_boost_spread");
// Gamma correction
gamma = rangelim(gamma, 0.5f, 3.0f);
params.gamma = rangelim(gamma, 0.5f, 3.0f);
for (size_t i = 0; i < LIGHT_SUN; i++) {
float x = i;
x /= LIGHT_SUN;
float brightness = a * x * x * x + b * x * x + c * x;
float boost = d * std::exp(-((x - e) * (x - e)) / (2.0f * f * f));
brightness = powf(brightness + boost, 1.0f / gamma);
light_LUT[i] = rangelim((u32)(255.0f * brightness), 0, 255);
// 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;
}
light_LUT[LIGHT_SUN] = 255;
}
#endif