Refactor: Simplify the RSW directional light computation

This also accounts for the inverted Y axis, but makes it clearer that the sunlight origin is located directly above the map.

Core/FileFormats/RagnarokRSW.lua

@@ -253,16 +253,14 @@ function RagnarokRSW:DecodeEnvironmentalLightSources()
 end
 
 function RagnarokRSW:ComputeSunRayDirection(latitudeInDegrees, longitudeInDegrees)
-	local sunRayDirection = Vector3D(0, 1, 0)
+	local sunRayDirection = Vector3D(0, -1, 0)
 
-	local rotationAroundX = Matrix3D:CreateAxisRotationX(latitudeInDegrees)
+	local rotationAroundX = Matrix3D:CreateAxisRotationX(-latitudeInDegrees) -- Account for inverted Y axis
 	local rotationAroundY = Matrix3D:CreateAxisRotationY(longitudeInDegrees)
 
 	sunRayDirection:Transform(rotationAroundX)
 	sunRayDirection:Transform(rotationAroundY)
 
-	sunRayDirection.y = -1 * sunRayDirection.y
-
 	return sunRayDirection
 end