Update light decoding table size (#6696)

Fix old undiminish_light bug

src/light.cpp

@@ -24,9 +24,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #ifndef SERVER
 
-// Length of LIGHT_MAX + 1 means LIGHT_MAX is the last value.
-// LIGHT_SUN is read as LIGHT_MAX from here.
-u8 light_LUT[LIGHT_MAX + 1];
+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;
@@ -48,9 +46,9 @@ void set_light_table(float gamma)
 // Gamma correction
 	gamma = rangelim(gamma, 0.5f, 3.0f);
 
-	for (size_t i = 0; i < LIGHT_MAX; i++) {
+	for (size_t i = 0; i < LIGHT_SUN; i++) {
 		float x = i;
-		x /= LIGHT_MAX;
+		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);
@@ -58,6 +56,6 @@ void set_light_table(float gamma)
 		if (i > 1 && light_LUT[i] <= light_LUT[i - 1])
 			light_LUT[i] = light_LUT[i - 1] + 1;
 	}
-	light_LUT[LIGHT_MAX] = 255;
+	light_LUT[LIGHT_SUN] = 255;
 }
 #endif

src/light.h

@@ -18,7 +18,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 */
 
 #pragma once
-
+#include <cassert>
 #include "irrlichttypes.h"
 
 /*
@@ -54,11 +54,12 @@ inline u8 diminish_light(u8 light, u8 distance)
 
 inline u8 undiminish_light(u8 light)
 {
+	assert(light <= LIGHT_SUN);
 	// We don't know if light should undiminish from this particular 0.
 	// Thus, keep it at 0.
 	if (light == 0)
 		return 0;
-	if (light == LIGHT_MAX)
+	if (light >= LIGHT_MAX)
 		return light;
 
 	return light + 1;
@@ -84,9 +85,9 @@ extern const u8 *light_decode_table;
 // 0 <= return value <= 255
 inline u8 decode_light(u8 light)
 {
-	if (light > LIGHT_MAX)
-		light = LIGHT_MAX;
-
+	// assert(light <= LIGHT_SUN);
+	if (light > LIGHT_SUN)
+		light = LIGHT_SUN;
 	return light_decode_table[light];
 }
 
@@ -98,8 +99,8 @@ inline float decode_light_f(float light_f)
 
 	if (i <= 0)
 		return (float)light_decode_table[0] / 255.0;
-	if (i >= LIGHT_MAX)
-		return (float)light_decode_table[LIGHT_MAX] / 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;