diff --git a/EGkBBox3d.h b/EGkBBox3d.h
index 34c56a8..3b9bd48 100644
--- a/EGkBBox3d.h
+++ b/EGkBBox3d.h
@@ -122,9 +122,13 @@ class EGK_EXPORT BBox3d
                 if ( dSqDist < EPS_ZERO)
                    return 0 ;
                 return sqrt( dSqDist) ; }
+      std::vector<Point3d> GetVertices() const ;
+      Point3d GetVertex( int nVert) const ;
+      bool Overlaps( const Frame3d& frThis, const BBox3d& bbOther, const Frame3d& frOther) const ;
 
    private :
       bool IsValid( void) const ;
+      int ChooseVertex( const Vector3d& vtDir) const ;
 
    private :
       Point3d m_ptMin ;
diff --git a/EGkPlane3d.h b/EGkPlane3d.h
index d377703..0e896f8 100644
--- a/EGkPlane3d.h
+++ b/EGkPlane3d.h
@@ -19,6 +19,12 @@
 //-----------------------------------------------------------------------------
 class Plane3d
 {
+public:
+   enum Side { POS = + 1,
+               NEG = - 1,
+               ON = 0
+              } ;
+
    public :
       Plane3d( void) : m_vtN( V_NULL), m_dDist( 0) {}
       bool Set( double dDist, const Vector3d& vtN)
@@ -180,3 +186,27 @@ AreSamePlaneExact( const Plane3d plPlaneA, const Plane3d& plPlaneB)
             PointInPlaneExact( plPlaneA.GetPoint(), plPlaneB)) ;
 }
 
+//-----------------------------------------------------------------------------
+inline int
+OnWhichSide( const Plane3d plPlane, const Point3d& pt)
+{
+   Vector3d vtDir = pt - plPlane.GetPoint() ;
+   if ( ! vtDir.Normalize()) {
+      // cerco un punto diverso sul piano per calcolare la direzione del punto
+      // mi aspetto che pt fosse troppo vicino all'origine del piano
+      Vector3d vtX = plPlane.GetVersN() ^ ( pt - ORIG) ;
+      Point3d ptOrig2 = plPlane.GetPoint() + vtX * 5 ;
+      vtDir = pt - ptOrig2 ;
+      vtDir.Normalize() ;
+   }
+   double dSide = vtDir * plPlane.GetVersN() ;
+   int nSide ;
+   if ( abs( dSide) < EPS_SMALL)
+      nSide = Plane3d::Side::ON ;
+   else if ( dSide > 0)
+      nSide = Plane3d::Side::POS ;
+   else
+      nSide = Plane3d::Side::NEG ;
+   
+   return nSide ;
+}