#ifndef OSG_BILLBOARD
#define OSG_BILLBOARD 1

#include <osg/Matrix>
#include <osg/Geode>

namespace osg {

/** Billboard - a Geode which orientates its child osg::Drawable's to face
    the eye point.  Typical uses are for trees, or particle explosions.
*/
class SG_EXPORT Billboard : public Geode
{
    public:

        enum Mode {
            AXIAL_ROT,
            POINT_ROT_EYE,
            POINT_ROT_WORLD
        };

        Billboard();
        
        META_Node(Billboard);

        /** Set the axis about which all the billboard's drawable rotate. */
        inline void setAxis(const Vec3& axis)          { _axis = axis; }
        /** Get the axis about which all the billboard's drawable rotate. */
        inline const Vec3& getAxis() const             { return _axis; }

        /** Set the billboard rotation mode. */
        inline void setMode(const Mode mode)                 { _mode = mode; }
        /** Get the billboard rotation mode. */
        inline const Mode getMode() const                     { return _mode; }

        /** Set the position of specified drawable. */
        inline void setPos(int i,const Vec3& pos)      { _positionList[i] = pos; }
        /** Get the position of specified drawable. */
        inline const Vec3& getPos(int i) const         { return _positionList[i]; }
        
        /** PositionList represents a list of pivot points for each drawable.*/
        typedef std::vector<Vec3> PositionList;
        
        /** Get the PositionList from the billboard.*/
        inline PositionList& getPositionList()             { return _positionList; }
        
        /** Get a const PositionList from the billboard.*/
        inline const PositionList& getPositionList() const { return _positionList; }

        /** Add Drawable to Billboard with default position(0,0,0);
         *  If gset not NULL and is not contained in Billboard then increment its 
         *  reference count, and dirty the bounding box to cause it to recompute on 
         *  next getBound() and return true for success.  Otherwise return false.
         */
        virtual const bool addDrawable( Drawable *gset );

        /** Add Drawable to Geode at position pos.
         *  If gset not NULL and is not contained in Billboard then increment its 
         *  reference count, and dirty the bounding box to cause it to recompute on 
         *  next getBound() and return true for success.  Otherwise return false.
         */
        virtual const bool addDrawable(Drawable *gset,const Vec3& pos);

        /** Remove Drawable and associated position from Billboard.
         *  If gset is contained in Billboard then remove it from the geoset
         *  list and decrement its reference count, and dirty the 
         *  bounding box to cause it to recompute on next getBound() and
         *  return true for success.  If gset is not found then return false
         *  and do not the reference count of gset is left unchanged.
         */
        virtual const bool removeDrawable( Drawable *gset );

        void calcRotation(const Vec3& eye_local, const Vec3& pos_local,Matrix& mat) const;
        void calcTransform(const Vec3& eye_local, const Vec3& pos_local,Matrix& mat) const;

    protected:

        virtual ~Billboard();

        virtual const bool computeBound() const;


        Mode            _mode;
        Vec3            _axis;
        PositionList    _positionList;

};

};

#endif