John Denker:

Add a view debugging functions and represent the viewer quats in the property tree for debugging.

Do a nontrivial calculation, demonstrating how to find the 12:00 orientation given the view and the view offset.  it, and observe that the 12:00 direction does not change when you change the view offset, which is a nontrivial result.

Erik: This already proved to be useful since I now obserbed that the sky and fog coloring code depends on view offset rather that the view orientations. This is why those effects are out of line in some views.

src/Main/viewmgr.cxx

@@ -28,6 +28,7 @@
 #include "viewmgr.hxx"
 
 #include <string.h>		// strcmp
+#include <boost/format.hpp>
 
 #include <simgear/compiler.h>
 #include <simgear/sound/soundmgr_openal.hxx>
@@ -162,6 +163,9 @@ typedef double (FGViewMgr::*double_getter)() const;
 void
 FGViewMgr::bind ()
 {
+// for automatic untying:
+#define x(str) ((void)tied_props.push_back(str), str)
+
   // these are bound to the current view properties
   fgTie("/sim/current-view/heading-offset-deg", this,
 	&FGViewMgr::getViewHeadingOffset_deg,
@@ -212,10 +216,20 @@ FGViewMgr::bind ()
 	&FGViewMgr::getNear_m, &FGViewMgr::setNear_m);
   fgSetArchivable("/sim/current-view/ground-level-nearplane-m");
 
+  fgTie(x("/sim/current-view/view_orientation"), this,
+	&FGViewMgr::getCurrentViewOrientation);
+  fgTie(x("/sim/current-view/view_or_offset"), this,
+	&FGViewMgr::getCurrentViewOrOffset);
+
+  fgTie(x("/sim/current-view/view1200"), this,
+	&FGViewMgr::getCurrentView1200);
+
   SGPropertyNode *n = fgGetNode("/sim/current-view", true);
   n->tie("viewer-x-m", SGRawValuePointer<double>(&abs_viewer_position[0]));
   n->tie("viewer-y-m", SGRawValuePointer<double>(&abs_viewer_position[1]));
   n->tie("viewer-z-m", SGRawValuePointer<double>(&abs_viewer_position[2]));
+
+#undef x
 }
 
 void
@@ -236,6 +250,12 @@ FGViewMgr::unbind ()
   fgUntie("/sim/current-view/viewer-x-m");
   fgUntie("/sim/current-view/viewer-y-m");
   fgUntie("/sim/current-view/viewer-z-m");
+
+  list<const char*>::const_iterator it;
+  for (it = tied_props.begin(); it != tied_props.end(); it++){
+    fgUntie(*it);
+  }
+
 }
 
 void
@@ -290,6 +310,9 @@ FGViewMgr::update (double dt)
   setViewTargetYOffset_m(fgGetDouble("/sim/current-view/target-y-offset-m"));
   setViewTargetZOffset_m(fgGetDouble("/sim/current-view/target-z-offset-m"));
 
+  current_view_orientation = loop_view->getViewOrientation();
+  current_view_or_offset = loop_view->getViewOrientationOffset();
+
   // Update the current view
   do_axes();
   loop_view->update(dt);
@@ -298,7 +321,7 @@ FGViewMgr::update (double dt)
   // update audio listener values
   // set the viewer posotion in Cartesian coordinates in meters
   smgr->set_position( abs_viewer_position );
-  smgr->set_orientation( loop_view->getViewOrientation() );
+  smgr->set_orientation( current_view_orientation );
 
   // get the model velocity
   SGVec3f velocity = SGVec3f::zeros();
@@ -747,6 +770,54 @@ FGViewMgr::setViewAxisLat (double axis)
   axis_lat = axis;
 }
 
+static const char* fmt("%6.3f ; %6.3f %6.3f %6.3f");
+
+// current view orientation
+// This is a rotation relative to the earth-centered (ec)
+// refrence frame.
+// However, the components of this quaternion are expressed 
+// in the OpenGL camera system i.e. x-right, y-up, z-back.
+const char* FGViewMgr::getCurrentViewOrientation() const{
+  return str(boost::format(fmt)
+   % current_view_orientation.w()
+   % current_view_orientation.x()
+   % current_view_orientation.y()
+   % current_view_orientation.z() ).c_str();
+}
+
+// This rotation takes you from the 12:00 direction 
+// i.e. body attitude
+// to whatever the current view direction is.  
+// The components of this quaternion are expressed in 
+// the XYZ body frame.
+const char* FGViewMgr::getCurrentViewOrOffset() const{
+  return str(boost::format(fmt)
+   % current_view_or_offset.w()
+   % current_view_or_offset.x()
+   % current_view_or_offset.y()
+   % current_view_or_offset.z() ).c_str();
+}
+
+// This rotates the conventional aviation XYZ body system 
+// i.e.  x-forward, y-starboard, z-bottom
+// to the OpenGL camera system 
+// i.e. x-right, y-up, z-back.
+const SGQuatd q(-0.5, -0.5, 0.5, 0.5);
+
+// The current attitude of the aircraft, 
+// i.e. the 12:00 direction.
+// The components of this quaternion are expressed in 
+// the GL camera frame.
+const char* FGViewMgr::getCurrentView1200() const{
+  SGQuatd view1200 = current_view_orientation
+        * conj(q) * conj(current_view_or_offset) * q; 
+  return str(boost::format(fmt)
+   % view1200.w()
+   % view1200.x()
+   % view1200.y()
+   % view1200.z() ).c_str();
+}
+
 void
 FGViewMgr::do_axes ()
 {

src/Main/viewmgr.hxx

@@ -25,6 +25,7 @@
 #define _VIEWMGR_HXX
 
 #include <vector>
+#include <list>
 
 #include <simgear/compiler.h>
 #include <simgear/structure/subsystem_mgr.hxx>
@@ -76,6 +77,8 @@ public:
 
 private:
 
+    list<const char*> tied_props;
+
     double axis_long;
     double axis_lat;
 
@@ -116,6 +119,11 @@ private:
     void setViewAxisLat (double axis);
     int getView () const;
     void setView (int newview);
+// quaternion accessors:
+    const char* getCurrentViewOrientation() const;
+    const char* getCurrentViewOrOffset() const;
+    const char* getCurrentView1200() const;
+
     bool stationary () const;
 
     SGPropertyNode_ptr view_number;
@@ -125,6 +133,7 @@ private:
     SGVec3d abs_viewer_position;
 
     int current;
+    SGQuatd current_view_orientation, current_view_or_offset;
 
     SGSoundMgr *smgr;