Implemented inline bool is_not_permeable_light

src/inc/block.hpp

@@ -375,5 +375,24 @@ inline bool is_not_permeable_ray(block_id id)
 		return false;
 	}
 
+	return true;
+}
+
+// Returns false if a block is permeable to light. Otherwise, returns true.
+
+inline bool is_not_permeable_light(block_id id)
+{
+	if 
+	(
+		id == id_air ||
+
+		id == id_glass ||
+
+		is_cross(id)
+	)
+	{
+		return false;
+	}
+
 	return true;
 }