From Chuck Seberino, "Attached are modified versions of RotateCylinderDragger and Projector files that clean up the use of _onCylinder / isProjectionOnCylinder().

I have also made changes to the RotateCylinderDragger to provide a cylinder ring with a thickness.   It is totally optional, but IMHO makes the default behavior work better than a solid cylinder (which typically obscures the geometry you are trying to drag).  Gives it a bit more to grab, especially in the case where eyepoint and cylinder axis are near parallel.
"

src/osgManipulator/Projector.cpp

@@ -560,7 +560,7 @@ CylinderPlaneProjector::CylinderPlaneProjector()
 {
 }
 
-CylinderPlaneProjector::CylinderPlaneProjector(osg::Cylinder* cylinder) : CylinderProjector(cylinder)
+CylinderPlaneProjector::CylinderPlaneProjector(osg::Cylinder* cylinder) : CylinderProjector(cylinder), _parallelPlane(false)
 {
 }
 
@@ -597,7 +597,7 @@ bool CylinderPlaneProjector::project(const PointerInfo& pi, osg::Vec3d& projecte
     return true;
 }
 
-osg::Quat CylinderPlaneProjector::getRotation(const osg::Vec3d& p1, bool p1OnCyl, const osg::Vec3d& p2, bool p2OnCyl) const
+osg::Quat CylinderPlaneProjector::getRotation(const osg::Vec3d& p1, const osg::Vec3d& p2) const
 {
     if(_parallelPlane)
     {

src/osgManipulator/RotateCylinderDragger.cpp

@@ -22,6 +22,49 @@
 
 using namespace osgManipulator;
 
+namespace
+{
+
+//------------------------------------------------------------------------------
+osg::Geometry* createDiskGeometry(float radius, float offset, float z, unsigned int numSegments
+   )
+{
+   const float angleDelta = 2.0f*osg::PI/float(numSegments);
+   const unsigned int numPoints = (numSegments+1) * 2;
+   float angle = 0.0f;
+   osg::Vec3Array* vertexArray = new osg::Vec3Array(numPoints);
+   osg::Vec3Array* normalArray = new osg::Vec3Array(numPoints);
+   unsigned int p = 0;
+   for(unsigned int i = 0; i < numSegments; ++i,angle+=angleDelta)
+   {
+      float c = cosf(angle);
+      float s = sinf(angle);
+      // Outer point
+      (*vertexArray)[p].set(radius*c, radius*s, z);
+      (*normalArray)[p].set(0.0, 0.0, -1.0);
+      ++p;
+      // Inner point
+      (*vertexArray)[p].set((radius-offset)*c, (radius-offset)*s, z);
+      (*normalArray)[p].set(0.0, 0.0, -1.0);
+      ++p;
+   }
+   // do last points by hand to ensure no round off errors.
+   (*vertexArray)[p] = (*vertexArray)[0];
+   (*normalArray)[p] = (*normalArray)[0];
+   ++p;
+   (*vertexArray)[p] = (*vertexArray)[1];
+   (*normalArray)[p] = (*normalArray)[1];
+
+   osg::Geometry* geometry = new osg::Geometry;
+   geometry->setVertexArray(vertexArray);
+   geometry->setNormalArray(normalArray);
+   geometry->setNormalBinding(osg::Geometry::BIND_PER_VERTEX);
+   geometry->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::TRIANGLE_STRIP, 0, vertexArray->size()));
+   return geometry;
+}
+
+}
+
 RotateCylinderDragger::RotateCylinderDragger()
 {
     _projector = new CylinderPlaneProjector();
@@ -73,7 +116,6 @@ bool RotateCylinderDragger::handle(const PointerInfo& pointer, const osgGA::GUIE
 
                     _prevWorldProjPt = projectedPoint * _projector->getLocalToWorld();
                     _prevRotation = osg::Quat();
-                    _prevPtOnCylinder = _projector->isProjectionOnCylinder();
 
                     aa.requestRedraw();
                 }
@@ -91,8 +133,8 @@ bool RotateCylinderDragger::handle(const PointerInfo& pointer, const osgGA::GUIE
                 if (_projector->project(pointer, projectedPoint))
                 {
                     osg::Vec3d prevProjectedPoint = _prevWorldProjPt * _projector->getWorldToLocal();
-                    osg::Quat  deltaRotation = _projector->getRotation(prevProjectedPoint, _prevPtOnCylinder,
-                                                                      projectedPoint, _projector->isProjectionOnCylinder());
+                    osg::Quat  deltaRotation = _projector->getRotation(prevProjectedPoint,
+                                                                      projectedPoint);
                     osg::Quat rotation = deltaRotation * _prevRotation;
 
                     // Generate the motion command.
@@ -106,7 +148,6 @@ bool RotateCylinderDragger::handle(const PointerInfo& pointer, const osgGA::GUIE
 
                     _prevWorldProjPt = projectedPoint * _projector->getLocalToWorld();
                     _prevRotation = rotation;
-                    _prevPtOnCylinder = _projector->isProjectionOnCylinder();
                     aa.requestRedraw();
                 }
                 return true; 
@@ -138,6 +179,34 @@ bool RotateCylinderDragger::handle(const PointerInfo& pointer, const osgGA::GUIE
 void RotateCylinderDragger::setupDefaultGeometry()
 {
     osg::Geode* geode = new osg::Geode;
-    geode->addDrawable(new osg::ShapeDrawable(const_cast<osg::Cylinder*>(_projector->getCylinder())));
+    {
+        osg::TessellationHints* hints = new osg::TessellationHints;
+        hints->setCreateTop(false);
+        hints->setCreateBottom(false);
+        hints->setCreateBackFace(false);
+
+        float radius    = 1.0f;
+        float height    = 0.1f;
+        float thickness = 0.1f;
+
+        // outer cylinder
+        osg::Cylinder* cylinder = new osg::Cylinder;
+        cylinder->setHeight(height);
+        cylinder->setRadius(radius);
+        osg::ShapeDrawable* cylinderDrawable = new osg::ShapeDrawable(cylinder, hints);
+        geode->addDrawable(cylinderDrawable);
+
+        // inner cylinder
+        osg::Cylinder* cylinder1 = const_cast<osg::Cylinder*>(_projector->getCylinder());
+        cylinder1->setHeight(height);
+        cylinder1->setRadius(radius-thickness);
+        osg::ShapeDrawable* cylinderDrawable1 = new osg::ShapeDrawable(cylinder1, hints);
+        geode->addDrawable(cylinderDrawable1);
+
+        // top
+        geode->addDrawable(createDiskGeometry(radius, thickness,  height/2, 100));
+        // bottom
+        geode->addDrawable(createDiskGeometry(radius, thickness, -height/2, 100));
+    }
     addChild(geode);
 }