X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=src%2Flight.cpp;h=d5389b45060a098df3964b228e5d26ffaedbdc40;hb=707c8c1e95d8db2d84909e7957b4dc9138e05599;hp=9b6f5c210ee7df4da84ff2208328a3b165eafe89;hpb=91d244c5229695933bf8510b01e06f922f062359;p=minetest.git

diff --git a/src/light.cpp b/src/light.cpp
index 9b6f5c210..d5389b450 100644
--- a/src/light.cpp
+++ b/src/light.cpp
@@ -18,6 +18,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 */
 
 #include "light.h"
+#include <algorithm>
 #include <cmath>
 #include "util/numeric.h"
 #include "settings.h"
@@ -29,44 +30,48 @@ 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;
+	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;
@@ -77,9 +82,11 @@ void set_light_table(float gamma)
 		// 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;
+		}
 	}
 }