diff --git a/Tree.cpp b/Tree.cpp
index 227a65f..69ab52a 100644
--- a/Tree.cpp
+++ b/Tree.cpp
@@ -2956,8 +2956,9 @@ Tree::CreateCellPolygons( int nLeafId, POLYLINEMATRIX& vPolygons, POLYLINEMATRIX
    vEdgeVertex3d[2].push_back( m_mVert[nId][0]) ;
    vEdgeVertex3d[3].push_back( m_mVert[nId][1]) ;
    // la PolyLine è riempita a partire dal lato bottom
-   Point3d ptStart ;
+   Point3d ptStart, pt3d ;
    plCell.GetFirstPoint( ptStart) ;
+   plCell3d.GetFirstPoint( pt3d) ;
    INTVECTOR vEdge = { 2, 3, 0, 1} ;
    for ( int p = 0 ; p < 4 ; ++ p) {
       int j = vEdge[p] ;
@@ -2965,8 +2966,9 @@ Tree::CreateCellPolygons( int nLeafId, POLYLINEMATRIX& vPolygons, POLYLINEMATRIX
       if ( j == 3)
          next = 0 ;
       Point3d ptToAdd ;
-      while ( plCell.GetNextPoint( ptToAdd)  &&  ! AreSamePointExact( ptToAdd, vEdgeVertex[next][0])) {
+      while ( plCell.GetNextPoint( ptToAdd)  &&  plCell3d.GetNextPoint( pt3d)  &&  ! AreSamePointExact( ptToAdd, vEdgeVertex[next][0])) {
          vEdgeVertex[j].push_back( ptToAdd) ;
+         vEdgeVertex3d[j].push_back( pt3d) ;
       }
    }
    
@@ -3581,7 +3583,7 @@ Tree::AddVertex( int nId, const PNTMATRIX& vEdgeVertex, const PNTMATRIX& vEdgeVe
      // se su un edge devo fare dei controlli
      // edge 0
       if ( ptToAdd.x >= ptBL.x  &&  ptToAdd.x <= ptTR.x  &&  ptToAdd.y == ptTR.y  &&  abs( vDir.x) > 1 - EPS_SMALL) {
-         for ( int t = 0 ; t < (int)vEdgeVertex[0].size() ; ++ t) {
+         for ( int t = 1 ; t < (int)vEdgeVertex[0].size() ; ++ t) {
             Point3d ptIntermed = vEdgeVertex[0][t] ;
             if ( ptIntermed.x > ptToAdd.x  &&  ptIntermed.x < ptLast.x) {
                plTrimmedPoly.AddUPoint( c, ptIntermed) ;
@@ -3590,13 +3592,17 @@ Tree::AddVertex( int nId, const PNTMATRIX& vEdgeVertex, const PNTMATRIX& vEdgeVe
             }
          }
          plTrimmedPoly.AddUPoint( c, ptToAdd) ;
-         Point3d pt3d ; m_pSrfBz->GetPointD1D2( ptToAdd.x / SBZ_TREG_COEFF, ptToAdd.y / SBZ_TREG_COEFF, ISurfBezier::FROM_MINUS, ISurfBezier::FROM_MINUS, pt3d) ;
+         Point3d pt3d ;
+         if( ! AreSamePointApprox(ptToAdd, vEdgeVertex[1][0]))
+            m_pSrfBz->GetPointD1D2( ptToAdd.x / SBZ_TREG_COEFF, ptToAdd.y / SBZ_TREG_COEFF, ISurfBezier::FROM_MINUS, ISurfBezier::FROM_MINUS, pt3d) ;
+         else
+            pt3d = vEdgeVertex3d[1][0] ;
          plTrimmedPoly3d.AddUPoint( c, pt3d) ;
          ++ c ;
       }
      // edge 1
       else if ( ptToAdd.y >= ptBL.y  &&  ptToAdd.y <= ptTR.y  &&  ptToAdd.x == ptBL.x  &&  abs( vDir.y) > 1 - EPS_SMALL) {
-         for ( int t = 0 ; t < (int)vEdgeVertex[1].size() ; ++ t) {
+         for ( int t = 1 ; t < (int)vEdgeVertex[1].size() ; ++ t) {
             Point3d ptIntermed = vEdgeVertex[1][t] ;
             if ( ptIntermed.y > ptToAdd.y  &&  ptIntermed.y < ptLast.y) {
                plTrimmedPoly.AddUPoint( c, ptIntermed) ;
@@ -3605,13 +3611,17 @@ Tree::AddVertex( int nId, const PNTMATRIX& vEdgeVertex, const PNTMATRIX& vEdgeVe
             }
          }
          plTrimmedPoly.AddUPoint( c, ptToAdd) ;
-         Point3d pt3d ; m_pSrfBz->GetPointD1D2( ptToAdd.x / SBZ_TREG_COEFF, ptToAdd.y / SBZ_TREG_COEFF, ISurfBezier::FROM_MINUS, ISurfBezier::FROM_MINUS, pt3d) ;
+         Point3d pt3d ;
+         if( ! AreSamePointApprox(ptToAdd, vEdgeVertex[2][0]))
+            m_pSrfBz->GetPointD1D2( ptToAdd.x / SBZ_TREG_COEFF, ptToAdd.y / SBZ_TREG_COEFF, ISurfBezier::FROM_MINUS, ISurfBezier::FROM_MINUS, pt3d) ;
+         else
+            pt3d = vEdgeVertex3d[2][0] ;
          plTrimmedPoly3d.AddUPoint( c, pt3d) ;
          ++ c ;
       }
      // edge 2
       else if ( ptToAdd.x >= ptBL.x  &&  ptToAdd.x <= ptTR.x  &&  ptToAdd.y == ptBL.y  &&  abs( vDir.x) > 1 - EPS_SMALL) {
-         for ( int t = 0 ; t < (int)vEdgeVertex[2].size() ; ++ t) {
+         for ( int t = 1 ; t < (int)vEdgeVertex[2].size() ; ++ t) {
             Point3d ptIntermed = vEdgeVertex[2][t] ;
             if ( ptIntermed.x < ptToAdd.x  &&  ptIntermed.x > ptLast.x) {
                plTrimmedPoly.AddUPoint( c, ptIntermed) ;
@@ -3620,13 +3630,17 @@ Tree::AddVertex( int nId, const PNTMATRIX& vEdgeVertex, const PNTMATRIX& vEdgeVe
             }
          }
          plTrimmedPoly.AddUPoint( c, ptToAdd) ;
-         Point3d pt3d ; m_pSrfBz->GetPointD1D2( ptToAdd.x / SBZ_TREG_COEFF, ptToAdd.y / SBZ_TREG_COEFF, ISurfBezier::FROM_MINUS, ISurfBezier::FROM_MINUS, pt3d) ;
+         Point3d pt3d ;
+         if( ! AreSamePointApprox(ptToAdd, vEdgeVertex[3][0]))
+            m_pSrfBz->GetPointD1D2( ptToAdd.x / SBZ_TREG_COEFF, ptToAdd.y / SBZ_TREG_COEFF, ISurfBezier::FROM_MINUS, ISurfBezier::FROM_MINUS, pt3d) ;
+         else
+            pt3d = vEdgeVertex3d[3][0] ;
          plTrimmedPoly3d.AddUPoint( c, pt3d) ;
          ++ c ;
       }
      // edge 3
       else if ( ptToAdd.y >= ptBL.y  &&  ptToAdd.y <= ptTR.y  &&  ptToAdd.x == ptTR.x  &&  abs( vDir.y) > 1 - EPS_SMALL) {
-         for ( int t = 0 ; t < (int)vEdgeVertex[3].size() ; ++ t) {
+         for ( int t = 1 ; t < (int)vEdgeVertex[3].size() ; ++ t) {
             Point3d ptIntermed = vEdgeVertex[3][t] ;
             if ( ptIntermed.y < ptToAdd.y  &&  ptIntermed.y > ptLast.y) {
                plTrimmedPoly.AddUPoint( c, ptIntermed) ;
@@ -3635,7 +3649,11 @@ Tree::AddVertex( int nId, const PNTMATRIX& vEdgeVertex, const PNTMATRIX& vEdgeVe
             }
          }
          plTrimmedPoly.AddUPoint( c, ptToAdd) ;
-         Point3d pt3d ; m_pSrfBz->GetPointD1D2( ptToAdd.x / SBZ_TREG_COEFF, ptToAdd.y / SBZ_TREG_COEFF, ISurfBezier::FROM_MINUS, ISurfBezier::FROM_MINUS, pt3d) ;
+         Point3d pt3d ;
+         if( ! AreSamePointApprox(ptToAdd, vEdgeVertex[0][0]))
+            m_pSrfBz->GetPointD1D2( ptToAdd.x / SBZ_TREG_COEFF, ptToAdd.y / SBZ_TREG_COEFF, ISurfBezier::FROM_MINUS, ISurfBezier::FROM_MINUS, pt3d) ;
+         else
+            pt3d = vEdgeVertex3d[0][0] ;
          plTrimmedPoly3d.AddUPoint( c, pt3d) ;
          ++ c ;
       }