/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2005 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_LOD
#define OSG_LOD 1

#include <osg/Group>

namespace osg {

/** LOD - Level Of Detail group node which allows switching between children
    depending on distance from eye point.
    Typical uses are for load balancing - objects further away from
    the eye point are rendered at a lower level of detail, and at times
    of high stress on the graphics pipeline lower levels of detail can
    also be chosen.
    The children are ordered from most detailed (for close up views) to the least 
    (see from a distance), and a set of ranges are used to decide which LOD is used 
    at different view distances, the criteria used is child 'i' is used when 
    range[i]<dist<range[i+1] is true. This requires there to be n+1 range values where the number of
    children is n, since no maximum distance of infinity is assumed.  If the number of range values (m)
    is insufficient then the children m through to n will be ignored, only 0..m-1 will be used
    during rendering.
*/
class OSG_EXPORT LOD : public Group
{
    public :
    
        LOD();

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

        META_Node(osg, LOD);

        virtual void traverse(NodeVisitor& nv);
        
        virtual bool addChild(Node *child);

        virtual bool addChild(Node *child, float min, float max);

        virtual bool removeChildren(unsigned int pos,unsigned int numChildrenToRemove=1);

        typedef std::pair<float,float>  MinMaxPair;
        typedef std::vector<MinMaxPair> RangeList;
      
        /** Modes which control how the center of object should be determined when computing which child is active.*/
        enum CenterMode
        {
            USE_BOUNDING_SPHERE_CENTER,
            USER_DEFINED_CENTER
        };

        /** Set how the center of object should be determined when computing which child is active.*/
        void setCenterMode(CenterMode mode) { _centerMode=mode; }

        /** Get how the center of object should be determined when computing which child is active.*/
        CenterMode getCenterMode() const { return _centerMode; }

        /** Sets the object-space point which defines the center of the osg::LOD.  
            center is affected by any transforms in the hierarchy above the osg::LOD.*/
        inline void setCenter(const Vec3& center) { _centerMode=USER_DEFINED_CENTER; _userDefinedCenter = center; }
        
        /** return the LOD center point. */
        inline const Vec3& getCenter() const { if (_centerMode==USER_DEFINED_CENTER) return _userDefinedCenter; else return getBound().center(); }


        /** Set the object-space reference radius of the volume enclosed by the LOD. 
          * Used to detmine the bounding sphere of the LOD in the absense of any children.*/
        inline void setRadius(float radius) { _radius = radius; }
        
        /** Get the object-space radius of the volume enclosed by the LOD.*/
        inline float getRadius() const { return _radius; }



        /** Modes that control how the range values should be intepreted when computing which child is active.*/
        enum RangeMode
        {
            DISTANCE_FROM_EYE_POINT,
            PIXEL_SIZE_ON_SCREEN
        };
        
        /** Set how the range values should be intepreted when computing which child is active.*/
        void setRangeMode(RangeMode mode) { _rangeMode = mode; }

        /** Get how the range values should be intepreted when computing which child is active.*/
        RangeMode getRangeMode() const { return _rangeMode; }


        /** Sets the min and max visible ranges of range of specifiec child.
            Values are floating point distance specified in local objects coordinates.*/
        void setRange(unsigned int childNo, float min,float max);
        
        /** returns the min visible range for specified child.*/
        inline float getMinRange(unsigned int childNo) const { return _rangeList[childNo].first; }

        /** returns the max visible range for specified child.*/
        inline float getMaxRange(unsigned int childNo) const { return _rangeList[childNo].second; }
        
        /** returns the number of ranges currently set. 
          * An LOD which has been fully set up will have getNumChildren()==getNumRanges(). */
        inline unsigned int getNumRanges() const { return _rangeList.size(); }

        /** set the list of MinMax ranges for each child.*/
        inline void setRangeList(const RangeList& rangeList) { _rangeList=rangeList; }

        /** return the list of MinMax ranges for each child.*/
        inline const RangeList& getRangeList() const { return _rangeList; }

        virtual BoundingSphere computeBound() const;

    protected :
        virtual ~LOD() {}

        CenterMode                      _centerMode;
        Vec3                            _userDefinedCenter;
        float                           _radius;

        RangeMode                       _rangeMode;
        RangeList                       _rangeList;

};

}

#endif