OpenSceneGraph/include/osgUtil/TrackballManipulator

#ifndef OSGUTIL_TRACKBALLMANIPULATOR
#define OSGUTIL_TRACKBALLMANIPULATOR 1

#include <osgUtil/CameraManipulator>

namespace osgUtil{

class OSGUTIL_EXPORT TrackballManipulator : public CameraManipulator
{
    public:

	TrackballManipulator();
	virtual ~TrackballManipulator();

        /** Attach a node to the manipulator. 
            Automatically detaches previously attached node.
            setNode(NULL) detaches previously nodes.
            Is ignored by manipulators which do not require a reference model.*/
        virtual void setNode(osg::Node*);

        /** Return node if attached.*/
        virtual const osg::Node* getNode() const;

        /** Move the camera to the default position. 
            May be ignored by manipulators if home functionality is not appropriate.*/
        virtual void home(const GUIEventAdapter& ea,GUIActionAdapter& us);
        
        /** Start/restart the manipulator.*/
        virtual void init(const GUIEventAdapter& ea,GUIActionAdapter& us);


        /** handle events, return true if handled, false otherwise.*/
	virtual bool handle(const GUIEventAdapter& ea,GUIActionAdapter& us);

    private:

        /** Reset the internal GUIEvent stack.*/
        void flushMouseEventStack();
        /** Add the current mouse GUIEvent to internal stack.*/
        void addMouseEvent(const GUIEventAdapter& ea);

        /** For the give mouse movement calculate the movement of the camera.
            Return true is camera has moved and a redraw is required.*/
        bool calcMovement();

        void trackball(osg::Vec3& axis,float& angle, float p1x, float p1y, float p2x, float p2y);
        float tb_project_to_sphere(float r, float x, float y);


        /** Check the speed at which the mouse is moving.
            If speed is below a threshold then return false, otherwise return true.*/
        bool isMouseMoving();

        // Internal event stack comprising last three mouse events.
        osg::ref_ptr<const GUIEventAdapter> _ga_t1;
        osg::ref_ptr<const GUIEventAdapter> _ga_t0;

        osg::ref_ptr<osg::Node>       _node;

        float _modelScale;
        float _minimumZoomScale;

        bool _thrown;

};

}

#endif