+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 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 > 0 && light_LUT[i] <= light_LUT[i - 1]) {
+ light_LUT[i] = std::min((u8)254, light_LUT[i - 1]) + 1;
+ }
+ }
+}