// 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; // 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 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 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
- const float a = alpha + beta - 2.0f;
- const float b = 3.0f - 2.0f * alpha - beta;
- const float 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");
-// 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);
+// 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;
+// 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;
+ 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