GUI picks only traverse nodes with PICK_BIT set.

(Which is all nodes except those which explicitly opt out,
such as lights, skydome, for the moment)

src/Viewer/CameraGroup.cxx

@@ -1193,7 +1193,8 @@ static bool computeCameraIntersection(const CameraInfo* cinfo, const osg::Vec2d&
                                Vec3d(start.x(), start.y(), start.z()),
                                Vec3d(end.x(), end.y(), end.z()));
   osgUtil::IntersectionVisitor iv(picker.get());
-  iv.setTraversalMask( ~simgear::MODELLIGHT_BIT );
+  iv.setTraversalMask( simgear::PICK_BIT );
+    
   const_cast<Camera*>(camera)->accept(iv);
   if (picker->containsIntersections()) {
     intersections = picker->getIntersections();