#define FG_FOV_MAX 179.9
+/**
+ * Representation of a single viewpoint in the FlightGear world.
+ */
+class FGViewPoint
+{
+public:
+ FGViewPoint ();
+ virtual ~FGViewPoint ();
+
+ /**
+ * Set the geodetic position for the view point.
+ */
+ virtual void setPosition (double lon_deg, double lat_deg, double alt_ft);
+
+
+ /**
+ * Get the longitude in degrees.
+ */
+ virtual double getLongitude_deg () const { return _lon_deg; }
+
+ /**
+ * Get the latitude in degrees.
+ */
+ virtual double getLatitude_deg () const { return _lat_deg; }
+
+ /**
+ * Get the altitude in feet ASL.
+ */
+ virtual double getAltitudeASL_ft () const { return _alt_ft; }
+
+ /**
+ * Get the absolute view position in fgfs coordinates.
+ */
+ virtual const double * getAbsoluteViewPos () const;
+
+
+ /**
+ * Get the relative view position in fgfs coordinates.
+ *
+ * The position is relative to the scenery centre.
+ */
+ virtual const float * getRelativeViewPos () const;
+
+
+ /**
+ * Get the absolute zero-elevation view position in fgfs coordinates.
+ */
+ virtual const float * getZeroElevViewPos () const;
+
+private:
+
+ void recalc () const;
+
+ mutable sgdVec3 _absolute_view_pos;
+ mutable sgVec3 _relative_view_pos;
+ mutable sgVec3 _zero_elev_view_pos;
+
+ bool _dirty;
+ double _lon_deg;
+ double _lat_deg;
+ double _alt_ft;
+
+};
+
+
// Define a structure containing view information
class FGViewer {
fgViewType _type;
fgScalingType scalingType;
+ FGViewPoint view_point;
+
// the nominal field of view (angle, in degrees)
double fov;