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-rw-r--r--src/light.cpp57
-rw-r--r--src/light.h16
-rw-r--r--src/util/numeric.h5
3 files changed, 47 insertions, 31 deletions
diff --git a/src/light.cpp b/src/light.cpp
index c63ffc3bd..c60f8eaca 100644
--- a/src/light.cpp
+++ b/src/light.cpp
@@ -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);
-
- 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);
+ params.gamma = rangelim(gamma, 0.5f, 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;
}
- light_LUT[LIGHT_SUN] = 255;
}
+
#endif
diff --git a/src/light.h b/src/light.h
index 203bd851e..44082a163 100644
--- a/src/light.h
+++ b/src/light.h
@@ -63,21 +63,7 @@ inline u8 decode_light(u8 light)
// 0.0 <= light <= 1.0
// 0.0 <= return value <= 1.0
-inline float decode_light_f(float light_f)
-{
- s32 i = (u32)(light_f * LIGHT_MAX + 0.5);
-
- if (i <= 0)
- return (float)light_decode_table[0] / 255.0;
- if (i >= LIGHT_SUN)
- return (float)light_decode_table[LIGHT_SUN] / 255.0;
-
- float v1 = (float)light_decode_table[i - 1] / 255.0;
- float v2 = (float)light_decode_table[i] / 255.0;
- float f0 = (float)i - 0.5;
- float f = light_f * LIGHT_MAX - f0;
- return f * v2 + (1.0 - f) * v1;
-}
+float decode_light_f(float light_f);
void set_light_table(float gamma);
diff --git a/src/util/numeric.h b/src/util/numeric.h
index 61370a3f4..b1e2845b8 100644
--- a/src/util/numeric.h
+++ b/src/util/numeric.h
@@ -243,6 +243,11 @@ inline s32 myround(f32 f)
return (s32)(f < 0.f ? (f - 0.5f) : (f + 0.5f));
}
+inline constexpr f32 sqr(f32 f)
+{
+ return f * f;
+}
+
/*
Returns integer position of node in given floating point position
*/