polygon.h

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#ifndef polygon_h
#define polygon_h

/*+
________________________________________________________________________

 (C) dGB Beheer B.V.; (LICENSE) http://opendtect.org/OpendTect_license.txt
 Author:        J.C. Glas
 Date:          Dec 2006
 RCS:           $Id$
________________________________________________________________________

-*/

#include "coord.h"
#include "typeset.h"
#include "iopar.h"
#include "bufstring.h"
#include "bendpointfinder.h"
#include <math.h>

template <class T>
mClass(Algo) ODPolygon
{
public:
                ODPolygon()
                    : closed_(true), udf_(Geom::Point2D<T>::udf())
                    , xrg_(mUdf(T),mUdf(T)), yrg_(mUdf(T),mUdf(T))      {} 
                
                ODPolygon(const TypeSet<Geom::Point2D<T> >& plg)
                    : poly_(plg), closed_(true)
                    , udf_(Geom::Point2D<T>::udf())
                    , xrg_(mUdf(T),mUdf(T)), yrg_(mUdf(T),mUdf(T))      {}

    void        erase();
    bool        isEmpty() const                 { return poly_.isEmpty(); }
                
    int         size() const                    { return poly_.size(); }
    bool        validIdx(int idx) const         { return poly_.validIdx(idx); }
    void        setEmpty()                      { erase(); }
    
    void        add(const Geom::Point2D<T>& vtx);
    void        remove(int idx);
    void        insert(int idx,const Geom::Point2D<T>& vtx);

    bool        isInside(const Geom::Point2D<T>&,
                         bool inclborder,T eps) const;
    
    int         isInside(const ODPolygon& testpoly,T eps=0) const;
                /*  0: testpoly fully outside (borders don't touch)
                    2: testpoly fully  inside (borders don't touch)
                    1: all intermediate cases */

    bool        segmentMeetsBorder(const Geom::Point2D<T>& pt1,
                                   const Geom::Point2D<T>& pt2,T eps) const;
    bool        windowOverlaps(const Interval<T>& xrange,
                               const Interval<T>& yrange,T eps) const;

                                // defined for closed polygon
    const Geom::Point2D<T>&     getVertex(int idx) const;
    const Geom::Point2D<T>&     nextVertex(int idx) const; 
    const Geom::Point2D<T>&     prevVertex(int idx) const;

    void        setClosed( bool yn )                    { closed_ = yn; }
    bool        isClosed() const                        { return closed_; }
    void        setUdf( Geom::Point2D<T> pt )           { udf_ = pt; }
    Geom::Point2D<T> getUdf() const                     { return udf_; }
    const TypeSet<Geom::Point2D<T> >& data() const      { return poly_; }

    Interval<T> getRange(bool of_x) const;
    void        getData(bool of_x,TypeSet<T>&) const;

    void        removeZeroLengths();
    bool        isUTurn(int idx) const;
    bool        isSelfIntersecting() const;

    void        convexHull();
    void        keepBendPoints(float eps);
    
                // not for self-intersecting polygons
    double      area() const            { return fabs(sgnArea2<double>()/2.0); }
    bool        clockwise() const       { return sgnArea2<T>()<0; }
    bool        anticlockwise() const   { return sgnArea2<T>()>0; }

    void        reverse();

    double      distTo(const Geom::Point2D<T>& refpt,int* segmentidxptr=0,
                       double* fractionptr=0) const;

    double      maxDistToBorderEstimate(double maxrelerr=0.001) const;

    bool        operator==(const ODPolygon<T>&) const;
    bool        operator>( const ODPolygon<T>& plg ) const
                { return poly_.size()>plg.size(); }

protected:
 
    static int                  doSegmentsMeet( const Geom::Point2D<T>& p1,
                                    const Geom::Point2D<T>& p2,
                                    const Geom::Point2D<T>& q1,
                                    const Geom::Point2D<T>& q2,
                                    T eps );

    static bool                 isOnSegment( const Geom::Point2D<T>& pt,
                                    const Geom::Point2D<T>& pt0,
                                    const Geom::Point2D<T>& pt1,
                                    T eps );
    static bool                 isOnHalfLine( const Geom::Point2D<T>& point,
                                    const Geom::Point2D<T>& dirvec,
                                    const Geom::Point2D<T>& endvec,
                                    T eps );

    static bool                 isEdgeCrossing( const Geom::Point2D<T>& raydir,
                                    const Geom::Point2D<T>& raysrc,
                                    const Geom::Point2D<T>& vtx1,
                                    const Geom::Point2D<T>& vtx2 );

    static bool                 isOnLine( const Geom::Point2D<T>& point,
                                    const Geom::Point2D<T>& dirvec,
                                    const Geom::Point2D<T>& posvec,
                                    T eps );

    static bool                 isRightOfLine( const Geom::Point2D<T>& point,
                                    const Geom::Point2D<T>& dirvec,
                                    const Geom::Point2D<T>& posvec );

    static bool                 doCoincide( const Geom::Point2D<T>& point1,
                                    const Geom::Point2D<T>& point2,
                                    T eps=mDefEps );

    static double               sgnDistToLine( const Geom::Point2D<T>& point,
                                    const Geom::Point2D<T>& dirvec,
                                    const Geom::Point2D<T>& posvec );

    template <class ST> ST      sgnArea2() const;

    static double               distToSegment( const Geom::Point2D<T>& p1,
                                    const Geom::Point2D<T>& p2,
                                    const Geom::Point2D<T>& refpt,
                                    double* fractionptr=0 );

    TypeSet<Geom::Point2D<T> >  poly_;
    bool                        closed_;
    Geom::Point2D<T>            udf_;

    mutable Interval<T>         xrg_;
    mutable Interval<T>         yrg_;
};


template <class T> inline
bool ODPolygon<T>::operator==( const ODPolygon<T>& poly ) const
{
    if ( data() != poly.data() ) return false;
    return true;
}


template <class T> inline
void ODPolygon<T>::getData( bool forx, TypeSet<T>& ts ) const
{
    for ( int idx=0; idx<size(); idx++ )
    {
        const Geom::Point2D<T>& vtx = poly_[idx];
        ts += forx ? vtx.x : vtx.y;
    }
}


template <class T> inline
void fillPar( IOPar& iop, const ODPolygon<T>& poly, const char* inpkey )
{
    const BufferString keywd( inpkey ); const char* key = keywd.buf();
    iop.setYN( IOPar::compKey(key,"Closed"), poly.isClosed() );
    iop.set( IOPar::compKey(key,"Undef"), poly.getUdf().x, poly.getUdf().y );
    TypeSet<T> ts; poly.getData( true, ts );
    iop.set( IOPar::compKey(key,"Data.X"), ts );
    ts.erase(); poly.getData( false, ts );
    iop.set( IOPar::compKey(key,"Data.Y"), ts );
}


template <class T> inline
void usePar( const IOPar& iop, ODPolygon<T>& poly, const char* inpkey )
{
    const BufferString keywd( inpkey ); const char* key = keywd.buf();
    bool yn = false; iop.getYN( IOPar::compKey(key,"Closed"), yn );
    poly.setClosed( yn );
    Geom::Point2D<T> pt; iop.get( IOPar::compKey(key,"Undef"), pt.x, pt.y );
    poly.setUdf( pt );

    if (   !iop.find( IOPar::compKey(key,"Data.X") )
        || !iop.find( IOPar::compKey(key,"Data.Y") ) )
        return;

    poly.setEmpty(); TypeSet<T> tsx, tsy;
    iop.get( IOPar::compKey(key,"Data.X"), tsx );
    iop.get( IOPar::compKey(key,"Data.Y"), tsy );
    const int sz = tsx.size() > tsy.size() ? tsy.size() : tsx.size();
    for ( int idx=0; idx<sz; idx++ )
        poly.add( Geom::Point2D<T>(tsx[idx],tsy[idx]) );
}


template <class T> inline
void ODPolygon<T>::insert( int idx, const Geom::Point2D<T>& vtx )
{
    if ( idx>=0 && idx<=size() )
        poly_.insert( idx, vtx );
    xrg_.set( mUdf(T), mUdf(T) );
    yrg_.set( mUdf(T), mUdf(T) );
}


template <class T> inline
void ODPolygon<T>::erase()
{
    poly_.erase();
    xrg_.set( mUdf(T), mUdf(T) );
    yrg_.set( mUdf(T), mUdf(T) );
}


template <class T> inline
void ODPolygon<T>::add( const Geom::Point2D<T>& vtx )
{
    poly_+=vtx;
    xrg_.set( mUdf(T), mUdf(T) );
    yrg_.set( mUdf(T), mUdf(T) );
}


template <class T> inline
void ODPolygon<T>::remove( int idx )
{
    if ( poly_.validIdx(idx) )
        poly_.removeSingle( idx );
    xrg_.set( mUdf(T), mUdf(T) );
    yrg_.set( mUdf(T), mUdf(T) );
}


template <class T> inline
const Geom::Point2D<T>& ODPolygon<T>::getVertex( int idx ) const
{ return poly_.validIdx(idx) ? poly_[idx] : udf_; }


template <class T> inline
const Geom::Point2D<T>& ODPolygon<T>::nextVertex( int idx ) const
{ return getVertex( idx+1<size() ? idx+1 : 0 ); }


template <class T> inline
const Geom::Point2D<T>& ODPolygon<T>::prevVertex( int idx ) const
{ return getVertex( idx ? idx-1 : size()-1 ); }


template <class T> inline
Interval<T> ODPolygon<T>::getRange( bool forx ) const
{
    if ( poly_.isEmpty() ) return Interval<T>( udf_.x, udf_.y );
    Geom::Point2D<T> vtx0 = poly_[0];
    Interval<T> ret = forx ? xrg_ : yrg_;
    if ( !mIsUdf(ret.start) && !mIsUdf(ret.stop) )
        return ret;
    ret.start = ret.stop = forx ? vtx0.x : vtx0.y;
    for ( int idx=1; idx<size(); idx++ )
    {
        const Geom::Point2D<T>& vtx = poly_[idx];
        const T val = forx ? vtx.x : vtx.y;
        if ( val < ret.start )          ret.start = val;
        else if ( val > ret.stop )      ret.stop = val;
    }
    if ( forx )
        xrg_ = ret;
    else
        yrg_ = ret;
    return ret;
}


template <class T> inline
bool ODPolygon<T>::isInside( const Geom::Point2D<T>& point,
                             bool inclborder, T eps ) const
{
    const T abseps = eps<0 ? -eps : eps;
    if ( (!mIsUdf(xrg_.start) && !mIsUdf(xrg_.stop) &&
          (xrg_.start>point.x+abseps || xrg_.stop<point.x-abseps)) ||
         (!mIsUdf(yrg_.start) && !mIsUdf(yrg_.stop) &&
          (yrg_.start>point.y+abseps || yrg_.stop<point.y-abseps)) )
        return false;

    const Geom::Point2D<T> arbitrarydir( 1, 0 );

    bool nrcrossingsodd = false;
    for ( int idx=0; idx<size(); idx++ )
    {
        const Geom::Point2D<T>& vtxcurr = poly_[idx];
        const Geom::Point2D<T>& vtxnext = nextVertex( idx );

        if ( isOnSegment(point, vtxcurr, vtxnext, eps) )
            return inclborder;
        if ( isEdgeCrossing(arbitrarydir, point, vtxcurr, vtxnext) )
            nrcrossingsodd = !nrcrossingsodd;
    }

    return nrcrossingsodd;
}


template <class T> inline
bool ODPolygon<T>::segmentMeetsBorder( const Geom::Point2D<T>& pt1,
                                       const Geom::Point2D<T>& pt2,
                                       T eps ) const
{
    for ( int idx=0; idx<size(); idx++ )
    {
        const Geom::Point2D<T>& vtxcurr = poly_[idx];
        const Geom::Point2D<T>& vtxnext = nextVertex( idx );

        if ( doSegmentsMeet(pt1, pt2, vtxcurr, vtxnext, eps) )
            return true;
    }

    return false;
}


template <class T> inline
bool ODPolygon<T>::windowOverlaps( const Interval<T>& xrange,
                                   const Interval<T>& yrange,
                                   T eps ) const
{
    ODPolygon window;
    window.add( Geom::Point2D<T>(xrange.start, yrange.start) );
    window.add( Geom::Point2D<T>(xrange.stop, yrange.start) );
    window.add( Geom::Point2D<T>(xrange.stop,  yrange.stop) );
    window.add( Geom::Point2D<T>( xrange.start, yrange.stop) );

    return isInside( window, eps );
}


template <class T> inline
int ODPolygon<T>::isInside( const ODPolygon& testpoly, T eps ) const
{
    if ( isEmpty() || testpoly.isEmpty() )
        return 0;

    for ( int idx=0; idx<size(); idx++ )
    {
        const Geom::Point2D<T>& vtxcurr = poly_[idx];
        const Geom::Point2D<T>& vtxnext = nextVertex( idx );

        if ( testpoly.segmentMeetsBorder(vtxcurr, vtxnext, eps) )
            return 1;
    }

    if ( isInside(testpoly.poly_[0], false, eps) )
        return 2;

    return testpoly.isInside(poly_[0], false, eps) ? 1 : 0; 
}


template <class T> inline
void ODPolygon<T>::removeZeroLengths()
{
    const int startidx = isClosed() ? size()-1 : size()-2;
    for ( int idx=startidx; idx>=0; idx-- )
    {
        if ( poly_[idx]==nextVertex(idx) && size()>1 )
            remove(idx);
    }
}
        

template <class T> inline
bool ODPolygon<T>::isUTurn( int idx ) const
{
    if ( !validIdx(idx) || ( !isClosed() && (idx==0 || idx==size()-1) ) )
        return false;

    const Geom::Point2D<T>& vec1 = prevVertex(idx) - poly_[idx];
    const Geom::Point2D<T>& vec2 = nextVertex(idx) - poly_[idx];

    return vec1.x*vec2.y-vec1.y*vec2.x==0 && vec1.x*vec2.x+vec1.y*vec2.y>0;
}


template <class T> inline
bool ODPolygon<T>::isSelfIntersecting() const
{
    ODPolygon<T> plg = *this;
    plg.removeZeroLengths();

    const int stopidx = plg.isClosed() ? plg.size() : plg.size()-1;
    for ( int idx=0; idx<stopidx; idx++ )
    {
        if ( plg.isUTurn(idx) )
            return true;

        const Geom::Point2D<T>& vtxcurr = plg.poly_[idx];
        const Geom::Point2D<T>& vtxnext = plg.nextVertex( idx );

        for ( int idy=0; idy<stopidx; idy++ )
        {
            const int dif = abs( idx-idy );
            if ( dif<=1 || dif>=plg.size()-1 )
                continue;

            const Geom::Point2D<T>& pt1 = plg.poly_[idy];
            const Geom::Point2D<T>& pt2 = plg.nextVertex( idy );

            if ( vtxcurr==pt1 || vtxcurr==pt2 )
                return true;

            if ( isEdgeCrossing(vtxnext-vtxcurr, vtxcurr, pt1, pt2) &&
                 isEdgeCrossing(vtxcurr-vtxnext, vtxnext, pt1, pt2) )
                return true;
        }
    }
    return false;
}


template <class T> inline
int ODPolygon<T>::doSegmentsMeet( const Geom::Point2D<T>& p1,
                                  const Geom::Point2D<T>& p2,
                                  const Geom::Point2D<T>& q1,
                                  const Geom::Point2D<T>& q2,
                                  T eps )
{
    if ( isOnSegment(p1, q1, q2, eps) || isOnSegment(p2, q1, q2, eps) ||
         isOnSegment(q1, p1, p2, eps) || isOnSegment(q2, p1, p2, eps) )
        return 1;

    if ( p1==p2 || q1==q2 || !isEdgeCrossing(p2-p1, p1, q1, q2) ||
         !isEdgeCrossing(p1-p2, p2, q1, q2) )
        return 0;

    return 2;
}


template <class T> inline
bool ODPolygon<T>::isOnSegment( const Geom::Point2D<T>& pt,
                                const Geom::Point2D<T>& pt0,
                                const Geom::Point2D<T>& pt1,
                                T eps )
{
    return isOnHalfLine( pt, pt1-pt0, pt0, eps ) &&
           isOnHalfLine( pt, pt0-pt1, pt1, eps );
}


template <class T> inline
bool ODPolygon<T>::isOnHalfLine( const Geom::Point2D<T>& point,
                                 const Geom::Point2D<T>& dirvec,
                                 const Geom::Point2D<T>& endvec,
                                 T eps )
{
     if ( doCoincide(point, endvec, eps) )
         return true;
     if ( !isOnLine(point, dirvec, endvec, eps) )
         return false;
     const Geom::Point2D<T> rot90dirvec( -dirvec.y, dirvec.x );
     return isRightOfLine( point, rot90dirvec, endvec );
}


template <class T> inline
bool ODPolygon<T>::isEdgeCrossing( const Geom::Point2D<T>& raydir,
                                   const Geom::Point2D<T>& raysrc,
                                   const Geom::Point2D<T>& vtx1,
                                   const Geom::Point2D<T>& vtx2 )
{
    const bool vtx1right = isRightOfLine( vtx1, raydir, raysrc );
    const bool vtx2right = isRightOfLine( vtx2, raydir, raysrc );

    if ( vtx1right && !vtx2right )
        return !isRightOfLine( raysrc, vtx2-vtx1, vtx1 );
    if ( !vtx1right && vtx2right )
        return !isRightOfLine( raysrc, vtx1-vtx2, vtx2 );
    return false;
}


template <class T> inline
bool ODPolygon<T>::isOnLine( const Geom::Point2D<T>& point,
                             const Geom::Point2D<T>& dirvec,
                             const Geom::Point2D<T>& posvec,
                             T eps )
{
    const double signeddist = sgnDistToLine( point, dirvec, posvec );
    return signeddist * signeddist <= eps * eps;
}

template <class T> inline
bool ODPolygon<T>::isRightOfLine( const Geom::Point2D<T>& point,
                                  const Geom::Point2D<T>& dirvec,
                                  const Geom::Point2D<T>& posvec )
{
    return sgnDistToLine( point, dirvec, posvec ) > 0;
}


template <class T> inline
bool ODPolygon<T>::doCoincide( const Geom::Point2D<T>& point1,
                               const Geom::Point2D<T>& point2,
                               T eps )
{
    return point1.sqDistTo( point2 ) <= eps * eps;
}


template <class T> inline
double ODPolygon<T>::sgnDistToLine( const Geom::Point2D<T>& point,
                                    const Geom::Point2D<T>& dirvec,
                                    const Geom::Point2D<T>& posvec )
{
    const double nolinedist = 0;

    const double dirveclen = dirvec.distTo( Geom::Point2D<T>(0,0) );
    if ( mIsZero(dirveclen, mDefEps) )
        return nolinedist;
    const double substpointinlineeqn =
        dirvec.y * ( point.x - posvec.x )-dirvec.x * ( point.y - posvec.y );
    return substpointinlineeqn / dirveclen;
}


template <class T> 
template <class ST> inline
ST ODPolygon<T>::sgnArea2() const
{
    ST area2 = 0;

    const Geom::Point2D<T>& pt0 = poly_[0];
    for ( int idx=1; idx<size()-1; idx++ )
    {
        const Geom::Point2D<T>& pt1 = poly_[idx];
        const Geom::Point2D<T>& pt2 = nextVertex( idx );
        area2 += (ST) ( (pt1.x-pt0.x) * (pt2.y-pt0.y) - 
                        (pt2.x-pt0.x) * (pt1.y-pt0.y) );
    }
    
    return area2;
}


template <class T> inline
void ODPolygon<T>::convexHull()
{
    // Code based on the Graham scan algorithm (1972)

    setClosed( true );
    if ( size()<2 )
        return;

    // Find guaranteed vertex of the convex hull to become pivot
    Geom::Point2D<T> pivot = poly_[0];
    for ( int idx=1; idx<size(); idx++ )
    {
        const Geom::Point2D<T>& vtx = poly_[idx];
        if ( vtx.x<pivot.x || (vtx.x==pivot.x && vtx.y<pivot.y) )
            pivot = vtx;
    }   

    // Remove all pivot copies
    for ( int idx=size()-1; idx>=0; idx-- )
    {
        if ( pivot == poly_[idx] )
            //poly_.removeSingle( idx, false );
            poly_.removeSingle( idx );
    }

    // Angular sort of all pivot-to-point segments
    for ( int idx=size()-2; idx>=0; idx-- )
    {
        const Geom::Point2D<T>& vtx = poly_[idx];
        for ( int idy=size()-1; idy>idx; idy-- )
        {
            const Geom::Point2D<T>& vty = poly_[idy];
            const double dist = sgnDistToLine( vty, vtx-pivot, pivot );

            if ( dist > 0 )
                continue;

            if ( dist < 0 )
                poly_.insert( idy+1, vtx );
            else if ( pivot.sqDistTo(vtx) > pivot.sqDistTo(vty) )
                poly_[idy] = vtx;

            poly_.removeSingle( idx );
            break;
        }
    }

    // Expand convex hull incrementally by backward removal of inner points
    for ( int idx=size()-3; idx>=0; idx-- )
    {
        const Geom::Point2D<T>& vtx = poly_[idx];
        while ( idx<size()-2 )
        {
            const Geom::Point2D<T>& vty = poly_[idx+1];
            const Geom::Point2D<T>& vtz = poly_[idx+2];
            if ( isRightOfLine(vtz, vty-vtx, vtx) )
                break;

            poly_.removeSingle( idx+1 );
        }
    }

    poly_ += pivot;
    
    xrg_.set( mUdf(T), mUdf(T) );
    yrg_.set( mUdf(T), mUdf(T) );
}


template <class T> inline
void ODPolygon<T>::reverse()
{
    const int sz = poly_.size();
    for ( int idx=0; idx<sz/2-1; idx++ )
    {
        Geom::Point2D<T> temp = poly_[idx];
        poly_[idx] = poly_[sz-1-idx];
        poly_[sz-1-idx] = temp;
    }
    
    xrg_.set( mUdf(T), mUdf(T) );
    yrg_.set( mUdf(T), mUdf(T) );
}


template <class T> inline
double ODPolygon<T>::distToSegment( const Geom::Point2D<T>& p1,
                                    const Geom::Point2D<T>& p2,
                                    const Geom::Point2D<T>& refpt,
                                    double* fractionptr )
{
    double frac = 0;

    if ( p1 != p2 )
    {
        const Geom::Point2D<T> dif = p2 - p1;
        const double numerator = dif.x*(refpt.x-p1.x) + dif.y*(refpt.y-p1.y);
        frac = numerator / (dif.x*dif.x + dif.y*dif.y);

        if ( frac < 0 )
            frac = 0;
        if ( frac > 1 )
            frac = 1;
    }

    if ( fractionptr )
        *fractionptr = frac;

    const Geom::Point2D<T> pointonseg( (T)(p1.x * (1-frac) + p2.x * frac),
                                       (T)(p1.y * (1-frac) + p2.y * frac) );
    return refpt.distTo( pointonseg );
}


template <class T> inline
double ODPolygon<T>::distTo( const Geom::Point2D<T>& refpt,
                             int* segmentidxptr, double* fractionptr ) const
{
    const int sz = size();
    if ( !sz )
        return mUdf(double);

    double mindist = MAXDOUBLE;

    for ( int idx=(isClosed() ? sz-1 : sz-2); idx>=0; idx-- )
    {
        const Geom::Point2D<T>& pt1 = getVertex( idx );
        const Geom::Point2D<T>& pt2 = nextVertex( idx );
        double frac;
        const double dist = distToSegment( pt1, pt2, refpt, &frac );

        if ( mindist >= dist )
        {
            mindist = dist;
            if ( segmentidxptr )
                *segmentidxptr = idx;
            if ( fractionptr )
                *fractionptr = frac;
        }
    }

    return mindist;
}


template <class T> inline
double ODPolygon<T>::maxDistToBorderEstimate( double maxrelerr ) const
{
    if ( maxrelerr <= 0.0 )
        return mUdf(double);

    if ( size() < 3 )
        return isEmpty() ? mUdf(double) : 0.0;

    const double upperbound = mMIN( 0.5 * getRange(true).width(),
                                    0.5 * getRange(false).width() );
    if ( !upperbound )
        return 0.0;

    ODPolygon<double> poly;
    for ( int idx=0; idx<size(); idx++ )
    {
        const Geom::Point2D<T>& pt = getVertex(idx);
        poly.add( Geom::Point2D<double>(pt.x, pt.y) );
    }
        
    double maxdist = 0.0;
    for ( int idx=0; idx<poly.size(); idx++ )
    {
        Geom::Point2D<double> curpt = 
            (poly.prevVertex(idx)+poly.getVertex(idx)+poly.nextVertex(idx)) / 3;

        if ( !poly.isInside(curpt, false, mDefEps) )
            continue;

        double curdist = poly.distTo( curpt );
        double gamma = 0.1 * upperbound;

        for ( int step=0; step<100; step++ ) 
        {
            if ( curdist > maxdist )
                maxdist = curdist;

            // Gradient ascent
            Geom::Point2D<double> pt1 = curpt;
            Geom::Point2D<double> pt2 = curpt;
            const double delta = 0.0001 * upperbound;
            pt1.x += delta;
            pt2.y += delta;
            const double dist1 = poly.distTo( pt1 );
            const double dist2 = poly.distTo( pt2 );
            Geom::Point2D<double> nextpt( dist1-curdist, dist2-curdist );
            nextpt *= gamma/delta;
            nextpt += curpt;

            if ( !poly.isInside(nextpt, false, mDefEps) )
            {
                gamma *= 0.5;
                continue;
            }

            double nextdist = poly.distTo( nextpt );

            if ( nextdist <= curdist )
            {
                gamma *= 0.5;

                if ( curpt.distTo(nextpt) <= 2*maxrelerr*curdist )
                    break;
            }

            curpt = nextpt;
            curdist = nextdist;
        }
    }   
    return maxdist;
}


template <class T> inline
void ODPolygon<T>::keepBendPoints( float eps )
{
    removeZeroLengths();

    const int sz = size();
    if ( sz < 3 )
        return;

    const int extra = closed_ ? 1 : 0;

    TypeSet<Coord> coords;
    for ( int idx=-extra; idx<sz+extra; idx++ )
    {
        const Geom::Point2D<T>& vtx = getVertex( (sz+idx)%sz );
        coords += Coord( vtx.x, vtx.y );
    }

    BendPointFinder2D finder( coords, eps );
    finder.execute();    
    const TypeSet<int>& bendpoints = finder.bendPoints();

    int bpidx = bendpoints.size()-extra-1;
    if ( bpidx<0 )
        return;

    for ( int vtxidx=sz-1; vtxidx>=0; vtxidx-- )
    {
        if ( bpidx>=0 && vtxidx==bendpoints[bpidx]-extra )
            bpidx--;
        else
            remove( vtxidx );
    }

    if ( closed_ && poly_.size()>1 && poly_.first() != poly_.last() )
        poly_ += poly_.first();
}

#endif