/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield 
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * OpenSceneGraph Public License for more details.
*/

#ifndef OSG_BILLBOARD
#define OSG_BILLBOARD 1

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

namespace osg {

/** Billboard is a derived form of Geode that orients its osg::Drawable
  * children to face the eye point. Typical uses include trees and
  * particle explosions,
*/
class OSG_EXPORT Billboard : public Geode
{
    public:

        enum Mode {
            POINT_ROT_EYE,
            POINT_ROT_WORLD,
            AXIAL_ROT
        };

        Billboard();
        
        /** Copy constructor using CopyOp to manage deep vs shallow copy. */
        Billboard(const Billboard&,const CopyOp& copyop=CopyOp::SHALLOW_COPY);

        META_Node(osg, Billboard);

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

        /** Set the rotation axis for the billboard's child Drawables.
          * Only utilized when mode==AXIAL_ROT. */
        void setAxis(const Vec3& axis);
        /** Get the rotation axis. */
        inline const Vec3& getAxis() const { return _axis; }

        /** This normal defines child Drawables' front face direction when unrotated. */
        void setNormal(const Vec3& normal);
        /** Get the front face direction normal. */
        inline const Vec3& getNormal() const { return _normal; }


        /** Set the specified child Drawable's position. */
        inline void setPosition(unsigned int i,const Vec3& pos)      { _positionList[i] = pos; }
        /** Get the specified child Drawable's position. */
        inline const Vec3& getPosition(unsigned int i) const         { return _positionList[i]; }

        /** Type definition for pivot point position list. */
        typedef std::vector<Vec3> PositionList;
        
        /** Set the list of pivot point positions. */
        inline void setPositionList(PositionList& pl)       { _positionList=pl; }

        /** Get the list of pivot point positions. */
        inline PositionList& getPositionList()              { return _positionList; }
        
        /** Get a const list of pivot point positions. */
        inline const PositionList& getPositionList() const  { return _positionList; }

        /** Add a Drawable with a default position of Vec3(0,0,0).
          * Call the base-class Geode::addDrawble() to add the given Drawable
          * gset as a child. If Geode::addDrawable() returns true, add the
          * default position to the pivot point position list and return true.
          * Otherwise, return false. */
        virtual bool addDrawable( Drawable *gset );

        /** Add a Drawable with a specified position.
          * Call the base-class Geode::addDrawble() to add the given Drawable
          * gset as a child. If Geode::addDrawable() returns true, add the
          * given position pos to the pivot point position list and return true.
          * Otherwise, return false. */
        virtual bool addDrawable(Drawable *gset,const Vec3& pos);

        /** Remove a Drawable and its associated position.
          * If gset is a child, remove it, decrement its reference count,
          * remove its pivot point position. and return true.
          * Otherwise, return false. */
        virtual bool removeDrawable( Drawable *gset );
                

        bool computeMatrix(Matrix& modelview, const Vec3& eye_local, const Vec3& pos_local) const;

        virtual BoundingSphere computeBound() const;

    protected:

        virtual ~Billboard();

        enum AxisAligned
        {
            AXIAL_ROT_X_AXIS=AXIAL_ROT+1,
            AXIAL_ROT_Y_AXIS,
            AXIAL_ROT_Z_AXIS,
            POINT_ROT_WORLD_Z_AXIS,
            CACHE_DIRTY
        };


        Mode                                _mode;
        Vec3                                _axis;
        Vec3                                _normal;
        Matrix                              _rotateNormalToZAxis;
        PositionList                        _positionList;
        
        // used internally as cache of which what _axis is aligned to help
        // decide which method of rotation to use.
        int                                 _cachedMode;
        Vec3                                _side;
        void updateCache();

};

}

#endif