+// reference frame orientation.
+// This is the view orientation you get when you have no
+// view offset, i.e. the offset operator is the identity.
+//
+// For example, in the familiar "cockpit lookfrom" view,
+// the reference frame is equal to the aircraft attitude,
+// i.e. it is the view looking towards 12:00 straight ahead.
+//
+// FIXME: Somebody needs to figure out what is the reference
+// frame view for the other view modes.
+//
+// Conceptually, this quat represents a rotation relative
+// to the ECEF reference orientation, as described at
+// http://www.av8n.com/physics/coords.htm#sec-orientation
+//
+// See the NOTE concerning reference orientations, below.
+//
+// The components of this quat are expressed in
+// the conventional aviation basis set,
+// i.e. x=forward, y=starboard, z=bottom
+double FGViewMgr::getCurrentViewFrame_w() const{
+ return ((current_view_orientation*conj(fsb2sta())*conj(current_view_or_offset))).w();
+}
+double FGViewMgr::getCurrentViewFrame_x() const{
+ return ((current_view_orientation*conj(fsb2sta())*conj(current_view_or_offset))).x();
+}
+double FGViewMgr::getCurrentViewFrame_y() const{
+ return ((current_view_orientation*conj(fsb2sta())*conj(current_view_or_offset))).y();
+}
+double FGViewMgr::getCurrentViewFrame_z() const{
+ return ((current_view_orientation*conj(fsb2sta())*conj(current_view_or_offset))).z();
+}
+
+
+// view offset.
+// This rotation takes you from the aforementioned
+// reference frame view orientation to whatever
+// actual current view orientation is.
+//
+// The components of this quaternion are expressed in
+// the conventional aviation basis set,
+// i.e. x=forward, y=starboard, z=bottom
+double FGViewMgr::getCurrentViewOrOffset_w() const{
+ return current_view_or_offset.w();
+}
+double FGViewMgr::getCurrentViewOrOffset_x() const{
+ return current_view_or_offset.x();
+}
+double FGViewMgr::getCurrentViewOrOffset_y() const{
+ return current_view_or_offset.y();
+}
+double FGViewMgr::getCurrentViewOrOffset_z() const{
+ return current_view_or_offset.z();
+}
+
+
+// current view orientation.
+// This is a rotation relative to the earth-centered (ec)
+// reference frame.
+//
+// NOTE: Here we remove a factor of fsb2sta so that
+// the components of this quat are displayed using the
+// conventional ECEF basis set. This is *not* the way
+// the view orientation is stored in the views[] array,
+// but is easier for non-graphics hackers to understand.
+// If we did not remove this factor of fsb2sta here and
+// in getCurrentViewFrame, that would be equivalent to
+// the following peculiar reference orientation:
+// Suppose you are over the Gulf of Guinea, at (lat,lon) = (0,0).
+// Then the reference frame orientation can be achieved via:
+// -- The aircraft X-axis (nose) headed south.
+// -- The aircraft Y-axis (starboard wingtip) pointing up.
+// -- The aircraft Z-axis (belly) pointing west.
+// To say the same thing in other words, and perhaps more to the
+// point: If we use the OpenGL camera orientation conventions,
+// i.e. Xprime=starboard, Yprime=top, Zprime=aft, then the
+// aforementioned peculiar reference orientation at (lat,lon)
+// = (0,0) can be described as:
+// -- aircraft Xprime axis (starboard) pointed up
+// -- aircraft Yprime axis (top) pointed east
+// -- aircraft Zprime axis (aft) pointed north
+// meaning the OpenGL axes are aligned with the ECEF axes.
+double FGViewMgr::getCurrentViewOrientation_w() const{
+ return (current_view_orientation * conj(fsb2sta())).w();
+}
+double FGViewMgr::getCurrentViewOrientation_x() const{
+ return (current_view_orientation * conj(fsb2sta())).x();
+}
+double FGViewMgr::getCurrentViewOrientation_y() const{
+ return (current_view_orientation * conj(fsb2sta())).y();
+}
+double FGViewMgr::getCurrentViewOrientation_z() const{
+ return (current_view_orientation * conj(fsb2sta())).z();
+}
+