From 79e393cf4b5027eb9071df23f4834aac3f3a689f Mon Sep 17 00:00:00 2001 From: Vitaliy Date: Sun, 16 Sep 2018 19:59:42 +0300 Subject: Light curve: Simplify and improve code, fix darkened daytime sky (#7693) --- src/light.cpp | 57 +++++++++++++++++++++++++++++++++++++++--------------- src/light.h | 16 +-------------- src/util/numeric.h | 5 +++++ 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 */ -- cgit v1.2.3