*/
#include "light.h"
+#include <algorithm>
#include <cmath>
#include "util/numeric.h"
#include "settings.h"
// 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;
+ float a, b, c; // Lighting curve polynomial coefficients
+ float boost, center, sigma; // Lighting curve parametric boost
+ float gamma; // Lighting curve gamma correction
};
static LightingParams params;
+
float decode_light_f(float x)
{
- if (x >= 1.0f) // x is equal to 1.0f half the time
+ if (x >= 1.0f) // x is often 1.0f
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
+ brightness += params.boost *
+ std::exp(-0.5f * sqr((x - params.center) / params.sigma));
+ if (brightness <= 0.0f) // May happen if parameters are extreme
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)
{
-// Lighting curve derivatives
- const float alpha = g_settings->getFloat("lighting_alpha");
- const float beta = g_settings->getFloat("lighting_beta");
-// Lighting curve coefficients
+// Lighting curve bounding gradients
+ const float alpha = rangelim(g_settings->getFloat("lighting_alpha"), 0.0f, 3.0f);
+ const float beta = rangelim(g_settings->getFloat("lighting_beta"), 0.0f, 3.0f);
+// Lighting curve polynomial coefficients
params.a = alpha + beta - 2.0f;
params.b = 3.0f - 2.0f * alpha - beta;
params.c = alpha;
-// Mid boost
- 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
- params.gamma = rangelim(gamma, 0.5f, 10.0f);
+// Lighting curve parametric boost
+ params.boost = rangelim(g_settings->getFloat("lighting_boost"), 0.0f, 0.4f);
+ params.center = rangelim(g_settings->getFloat("lighting_boost_center"), 0.0f, 1.0f);
+ params.sigma = rangelim(g_settings->getFloat("lighting_boost_spread"), 0.0f, 0.4f);
+// Lighting curve gamma correction
+ params.gamma = rangelim(gamma, 0.33f, 3.0f);
// Boundary values should be fixed
light_LUT[0] = 0;
// 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;
+ if (i > 0 && light_LUT[i] <= light_LUT[i - 1]) {
+ light_LUT[i] = std::min((u8)254, light_LUT[i - 1]) + 1;
+ }
}
}