RStarBoundingBox.h

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/*
 *  Copyright (c) 2008 Dustin Spicuzza <dustin@virtualroadside.com>
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of version 2 of the GNU General Public License
 *  as published by the Free Software Foundation.
 *
 *  This program 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
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */


#ifndef RStarBoundingBox_H
#define RStarBoundingBox_H

#include <limits>
#include <utility>
#include <cstddef>
#include <string>
#include <sstream>


template <std::size_t dimensions>
struct RStarBoundingBox {

        // edges[x].first is low value, edges[x].second is high value
        std::pair<double, double> edges[dimensions];
        
        // forces all edges to their extremes so we can stretch() it
        void reset()
        {
                for (std::size_t axis = 0; axis < dimensions; axis++)
                {
                        edges[axis].first = std::numeric_limits<double>::max();
                        edges[axis].second = std::numeric_limits<double>::min();
                }
        }
        
        // returns a new bounding box that has the maximum boundaries
        static RStarBoundingBox MaximumBounds()
        {
                RStarBoundingBox<dimensions> bound;
                bound.reset();
                return bound;
        }
        

        // fits another box inside of this box, returns true if a stretch occured
        bool stretch(const RStarBoundingBox<dimensions> &bb)
        {
                bool ret = false;
                
                for (std::size_t axis = 0; axis < dimensions; axis++)
                {
                        
                        if (edges[axis].first > bb.edges[axis].first)
                        {
                                edges[axis].first = bb.edges[axis].first;
                                ret = true;
                        }
                
                        if (edges[axis].second < bb.edges[axis].second)
                        {
                                edges[axis].second = bb.edges[axis].second;
                                ret = true;
                        }
                }
                        
                return ret;
        }
        
        // the sum of all deltas between edges
        inline int edgeDeltas() const
        {
                double distance = 0;
                for (std::size_t axis = 0; axis < dimensions; axis++)
                        distance += edges[axis].second - edges[axis].first;
                        
                return distance;
        }
        
        // calculates the area of a bounding box
        inline double area() const
        {
                double area = 1;
                for (std::size_t axis = 0; axis < dimensions; axis++)
                        area *= (double)(edges[axis].second - edges[axis].first);
                
                return area;
        }
        
        // this determines if a bounding box is fully contained within this bounding box
        inline bool encloses(const RStarBoundingBox<dimensions>& bb) const
        {
                // if (y1 < x1 || x2 < y2)
                for (std::size_t axis = 0; axis < dimensions; axis++)
                        if (bb.edges[axis].first < edges[axis].first || edges[axis].second < bb.edges[axis].second)
                                return false;
                
                return true;
        }
        
        // a quicker way to determine if two bounding boxes overlap
        inline bool overlaps(const RStarBoundingBox<dimensions>& bb) const
        {
                // do it this way so theres no equal signs (in case of doubles)
                // if (!(x1 < y2) && !(x2 > y1))
                for (std::size_t axis = 0; axis < dimensions; axis++)
                {               
                        if (!(edges[axis].first < bb.edges[axis].second) || !(bb.edges[axis].first < edges[axis].second))
                                return false;
                }

                return true;
        }
        
        // calculates the total overlapping area of two boxes
        double overlap(const RStarBoundingBox<dimensions>& bb) const
        {
                double area = 1.0;
                for (std::size_t axis = 0; area && axis < dimensions; axis++)
                {
                        // this makes it easier to understand
                        const double x1 = edges[axis].first;
                        const double x2 = edges[axis].second;
                        const double y1 = bb.edges[axis].first;
                        const double y2 = bb.edges[axis].second;
                
                        // left edge outside left edge
                        if (x1 < y1)
                        {
                                // and right edge inside left edge
                                if (y1 < x2)
                                {
                                        // right edge outside right edge
                                        if (y2 < x2)
                                                area *= (double)( y2 - y1 );
                                        else
                                                area *= (double)( x2 - y1 );
                                                
                                        continue;
                                }
                        }
                        // right edge inside left edge
                        else if (x1 < y2)
                        {
                                // right edge outside right edge
                                if (x2 < y2)
                                        area *= (double)( x2 - x1 );
                                else
                                        area *= (double)( y2 - x1 );
                                        
                                continue;
                        }
                        
                        // if we get here, there is no overlap
                        return 0.0;
                }

                return area;
        }
        
        // sums the total distances from the center of another bounding box
        double distanceFromCenter(const RStarBoundingBox<dimensions>& bb) const
        {
                double distance = 0, t;
                for (std::size_t axis = 0; axis < dimensions; axis++)
                {
                        t = ((double)edges[axis].first + (double)edges[axis].second + 
                             (double)bb.edges[axis].first + (double)bb.edges[axis].second)
                                 /2.0;
                        distance += t*t;
                }
                        
                return distance;
        }
        
        // determines if two bounding boxes are identical
        bool operator==(const RStarBoundingBox<dimensions>& bb)
        {
                for (std::size_t axis = 0; axis < dimensions; axis++)
                        if (edges[axis].first != bb.edges[axis].first || edges[axis].second != bb.edges[axis].second)
                                return false;
                        
                return true;
        }
        
        
        // very slow, use for debugging only
        std::string ToString() const
        {
                std::stringstream name("");
                name << "[";
                for (std::size_t axis = 0; axis < dimensions; axis++)
                {
                        name << "(" << edges[axis].first << "," << edges[axis].second << ")";
                        if (axis != dimensions -1)
                                name << ",";
                }
                name << "]";
                
                return name.str();
        }
};



template <std::size_t dimensions>
struct RStarBoundedItem {
        typedef RStarBoundingBox<dimensions> BoundingBox;

        BoundingBox bound;
};


/**********************************************************
 * Functor used to iterate over a set and stretch a
 * bounding box
 **********************************************************/

// for_each(items.begin(), items.end(), StretchBoundedItem::BoundingBox(bound));
template <typename BoundedItem>
struct StretchBoundingBox : 
        public std::unary_function< const BoundedItem * const, void >
{
        typename BoundedItem::BoundingBox * m_bound;
        explicit StretchBoundingBox(typename BoundedItem::BoundingBox * bound) : m_bound(bound) {}

        void operator() (const BoundedItem * const item)
        {
                m_bound->stretch(item->bound);
        }
};


/**********************************************************
 * R* Tree related functors used for sorting BoundedItems
 *
 * TODO: Take advantage of type traits
 **********************************************************/

template <typename BoundedItem>
struct SortBoundedItemsByFirstEdge : 
        public std::binary_function< const BoundedItem * const, const BoundedItem * const, bool >
{
        const std::size_t m_axis;
        explicit SortBoundedItemsByFirstEdge (const std::size_t axis) : m_axis(axis) {}
        
        bool operator() (const BoundedItem * const bi1, const BoundedItem * const bi2) const 
        {
                return bi1->bound.edges[m_axis].first < bi2->bound.edges[m_axis].first;
        }
};

template <typename BoundedItem>
struct SortBoundedItemsBySecondEdge : 
        public std::binary_function< const BoundedItem * const, const BoundedItem * const, bool >
{
        const std::size_t m_axis;
        explicit SortBoundedItemsBySecondEdge (const std::size_t axis) : m_axis(axis) {}

        bool operator() (const BoundedItem * const bi1, const BoundedItem * const bi2) const 
        {
                return bi1->bound.edges[m_axis].second < bi2->bound.edges[m_axis].second;
        }
};


template <typename BoundedItem>
struct SortBoundedItemsByDistanceFromCenter : 
        public std::binary_function< const BoundedItem * const, const BoundedItem * const, bool >
{
        const typename BoundedItem::BoundingBox * const m_center;
        explicit SortBoundedItemsByDistanceFromCenter(const typename BoundedItem::BoundingBox * const center) : m_center(center) {}

        bool operator() (const BoundedItem * const bi1, const BoundedItem * const bi2) const 
        {
                return bi1->bound.distanceFromCenter(*m_center) < bi2->bound.distanceFromCenter(*m_center);
        }
};

template <typename BoundedItem>
struct SortBoundedItemsByAreaEnlargement : 
        public std::binary_function< const BoundedItem * const, const BoundedItem * const, bool >
{
        const double area;
        explicit SortBoundedItemsByAreaEnlargement(const typename BoundedItem::BoundingBox * center) : area(center->area()) {}

        bool operator() (const BoundedItem * const bi1, const BoundedItem * const bi2) const 
        {
                return area - bi1->bound.area() < area - bi2->bound.area();
        }
};

template <typename BoundedItem>
struct SortBoundedItemsByOverlapEnlargement : 
        public std::binary_function< const BoundedItem * const, const BoundedItem * const, bool >
{
        const typename BoundedItem::BoundingBox * const m_center;
        explicit SortBoundedItemsByOverlapEnlargement(const typename BoundedItem::BoundingBox * const center) : m_center(center) {}

        bool operator() (const BoundedItem * const bi1, const BoundedItem * const bi2) const 
        {
                return bi1->bound.overlap(*m_center) < bi2->bound.overlap(*m_center);
        }
};


#endif