Added utility function to calculate the dew point

addons/weather/XEH_preInit.sqf

@@ -5,6 +5,7 @@ ADDON = false;
 
 PREP(calculateAirDensity);
 PREP(calculateBarometricPressure);
+PREP(calculateDewPoint);
 PREP(calculateHeatIndex);
 PREP(calculateRoughnessLength);
 PREP(calculateTemperatureAtHeight);

addons/weather/functions/fnc_calculateDewPoint.sqf

@@ -0,0 +1,27 @@
+/*
+ * Author: Ruthberg
+ *
+ * Calculates dew point based on temperature and relative humidity
+ *
+ * Arguments:
+ * 0: temperature - degrees celcius <NUMBER>
+ * 2: relativeHumidity - value between 0.0 and 1.0 <NUMBER>
+ *
+ * Return Value:
+ * 0: heat index <NUMBER>
+ *
+ * Return value:
+ * None
+ */
+#include "script_component.hpp"
+
+#define __b 17.67
+#define __c 243.5
+
+PARAMS_2(_t, _rh);
+
+// Source: https://en.wikipedia.org/wiki/Dew_point
+private ["_gamma"];
+_gamma = ln(_rh) + (__b * _t) / (__c + _t);
+
+(__c * _gamma) / (__b - _gamma)

addons/weather/functions/fnc_calculateHeatIndex.sqf

@@ -1,7 +1,7 @@
 /*
  * Author: Ruthberg
  *
- * Calculates heat index based on temperature and humidity
+ * Calculates heat index based on temperature and relative humidity
  *
  * Arguments:
  * 0: temperature - degrees celcius <NUMBER>