diff --git a/CAvToolSurfTm.cpp b/CAvToolSurfTm.cpp
index 0fcd4c2..acb6f3d 100644
--- a/CAvToolSurfTm.cpp
+++ b/CAvToolSurfTm.cpp
@@ -121,7 +121,8 @@ CAvToolSurfTm::SetGenTool( const ICurveComposite* pToolOutline)
 
 //----------------------------------------------------------------------------
 bool
-CAvToolSurfTm::TestPosition( const Point3d& ptT, const Vector3d& vtDir, const Vector3d& vtMove, double& dTotDist) const
+CAvToolSurfTm::TestPosition( const Point3d& ptT, const Vector3d& vtDir, const Vector3d& vtMove,
+                             double& dTotDist, Vector3d* pvtTriaN) const
 {
   // Se utensile non definito, errore
    if ( m_Tool.GetType() == Tool::UNDEF)
@@ -141,13 +142,19 @@ CAvToolSurfTm::TestPosition( const Point3d& ptT, const Vector3d& vtDir, const Ve
       if ( AreSameFrame( frMove, m_frMove)) {
         // Eseguo controllo
          Point3d ptCurr = ptT ;
-         dTotDist = MyTestPositionHG( ptCurr, vtDir) ;
+         Vector3d vtTriaN ;
+         dTotDist = MyTestPositionHG( ptCurr, vtDir, vtTriaN) ;
+         if ( pvtTriaN != nullptr)
+            *pvtTriaN = vtTriaN ;
          return ( dTotDist > - EPS_SMALL) ;
       }
    }
   // Altrimenti eseguo controllo diretto
    Point3d ptCurr = ptT ;
-   dTotDist = MyTestPosition( ptCurr, vtDir, vtMove) ;
+   Vector3d vtTriaN ;
+   dTotDist = MyTestPosition( ptCurr, vtDir, vtMove, vtTriaN) ;
+   if ( pvtTriaN != nullptr)
+      *pvtTriaN = vtTriaN ;
    return ( dTotDist > - EPS_SMALL) ;
 }
 
@@ -232,7 +239,8 @@ CAvToolSurfTm::TestSubSeries( int nId, PNTUVECTOR& vPntM, const Vector3d& vtDir,
   // Ciclo sui punti da verificare
    for ( int i = nFirst ; i <= nLast ; ++ i) {
      // verifico il punto
-      double dMove = MyTestPositionHG( vPntM[i].first, vtDir) ;
+      Vector3d vtTriaN ;
+      double dMove = MyTestPositionHG( vPntM[i].first, vtDir, vtTriaN) ;
       vPntM[i].second = dMove ;
       if ( dMove < - EPS_SMALL)
          return false ;
@@ -353,7 +361,8 @@ CAvToolSurfTm::TestSubPath( int nId, PNTULIST& lPntM, const Vector3d& vtDir, dou
    while ( itPntMCurr != lPntM.end()) {
      // verifico il punto
       ptCurr = itPntMCurr->first ;
-      double dMove = MyTestPositionHG( itPntMCurr->first, vtDir) ;
+      Vector3d vtTriaN ;
+      double dMove = MyTestPositionHG( itPntMCurr->first, vtDir, vtTriaN) ;
       itPntMCurr->second = dMove ;
       if ( dMove < - EPS_SMALL)
          return false ;
@@ -397,7 +406,8 @@ CAvToolSurfTm::MyTestMidPointHG( PNTULIST& lPntM, const PNTULIST::iterator& itPn
    Point3d ptMid = Media( ptPrev, ptCurr, 0.5) ;
   // ne effettuo la correzione per evitare la collisione
    Point3d ptNewMid = ptMid ;
-   double dMidMove = MyTestPositionHG( ptNewMid, vtDir) ;
+   Vector3d vtTriaN ;
+   double dMidMove = MyTestPositionHG( ptNewMid, vtDir, vtTriaN) ;
    if ( dMidMove < - EPS_SMALL)
       return false ;
   // massima distanza ammissibile
@@ -419,9 +429,10 @@ CAvToolSurfTm::MyTestMidPointHG( PNTULIST& lPntM, const PNTULIST::iterator& itPn
 
 //----------------------------------------------------------------------------
 double
-CAvToolSurfTm::MyTestPosition( Point3d& ptT, const Vector3d& vtDir, const Vector3d& vtMove) const
+CAvToolSurfTm::MyTestPosition( Point3d& ptT, const Vector3d& vtDir, const Vector3d& vtMove, Vector3d& vtTriaN) const
 {
    double dTotDist = 0 ;
+   vtTriaN = V_NULL ;
    for ( auto pStm : m_vSTM) {
       Triangle3d Tria ;
       for ( int nTria = pStm->GetFirstTriangle( Tria) ;
@@ -433,6 +444,7 @@ CAvToolSurfTm::MyTestPosition( Point3d& ptT, const Vector3d& vtDir, const Vector
          if ( dDist > EPS_SMALL) {
             dTotDist += dDist ;
             ptT += dDist * vtMove ;
+            vtTriaN = Tria.GetN() ;
          }
       }
    }
@@ -441,7 +453,7 @@ CAvToolSurfTm::MyTestPosition( Point3d& ptT, const Vector3d& vtDir, const Vector
 
 //----------------------------------------------------------------------------
 double
-CAvToolSurfTm::MyTestPositionHG( Point3d& ptT, const Vector3d& vtDir) const
+CAvToolSurfTm::MyTestPositionHG( Point3d& ptT, const Vector3d& vtDir, Vector3d& vtTriaN) const
 {
   // calcolo box utensile nel riferimento di movimento
    BBox3d b3Tool ;
@@ -463,6 +475,7 @@ CAvToolSurfTm::MyTestPositionHG( Point3d& ptT, const Vector3d& vtDir) const
    }
   // ciclo sui triangoli che intersecano box in 2d 
    double dTotDist = 0 ;
+   vtTriaN = V_NULL ;
    INTVECTOR vnIds ;
    if ( m_HGrids.Find( b3Tool, vnIds)) {
       for ( int i = 0 ; i < int( vnIds.size()) ; ++ i) {
@@ -478,6 +491,7 @@ CAvToolSurfTm::MyTestPositionHG( Point3d& ptT, const Vector3d& vtDir) const
          if ( dDist > EPS_SMALL) {
             dTotDist += dDist ;
             ptT += dDist * m_frMove.VersZ() ;
+            vtTriaN = Tria.GetN() ;
          }
          else if ( dDist < -EPS_SMALL)
             return -1 ;
diff --git a/CAvToolSurfTm.h b/CAvToolSurfTm.h
index 37201e9..7aaea3d 100644
--- a/CAvToolSurfTm.h
+++ b/CAvToolSurfTm.h
@@ -36,7 +36,8 @@ class CAvToolSurfTm : public ICAvToolSurfTm
                   { return m_Tool.GetHeigth() ; }
       const ICurveComposite& GetToolOutline( bool bApprox = false) const override
                   { return ( bApprox ? m_Tool.GetApproxOutline() : m_Tool.GetOutline()) ;}
-      bool TestPosition( const Point3d& ptT, const Vector3d& vtDir, const Vector3d& vtMove, double& dTotDist) const override ;
+      bool TestPosition( const Point3d& ptT, const Vector3d& vtDir, const Vector3d& vtMove,
+                         double& dTotDist, Vector3d* pvtTriaN = nullptr) const override ;
       bool TestSeries( PNTUVECTOR& vPntM, const Vector3d& vtDir, const Vector3d& vtMove, double dProgCoeff = 1) override ;
       bool TestPath( PNTULIST& lPntM, const Vector3d& vtDir, const Vector3d& vtMove, double dLinTol, double dProgCoeff = 1) override ;
 
@@ -47,8 +48,8 @@ class CAvToolSurfTm : public ICAvToolSurfTm
    private :
       bool   TestSubSeries( int nId, PNTUVECTOR& vPntM, const Vector3d& vtDir, int nFirst, int nLast, double dProgCoeff) ;
       bool   TestSubPath( int nId, PNTULIST& lPntM, const Vector3d& vtDir, double dLinTol, double dProgCoeff) ;
-      double MyTestPosition( Point3d& ptT, const Vector3d& vtDir, const Vector3d& vtMove) const ;
-      double MyTestPositionHG( Point3d& ptT, const Vector3d& vtDir) const ;
+      double MyTestPosition( Point3d& ptT, const Vector3d& vtDir, const Vector3d& vtMove, Vector3d& vtTriaN) const ;
+      double MyTestPositionHG( Point3d& ptT, const Vector3d& vtDir, Vector3d& vtTriaN) const ;
       bool   MyTestMidPointHG( PNTULIST& lPntM, const PNTULIST::iterator& itPntMPrev, const PNTULIST::iterator& itPntMCurr,
                                const Point3d& ptPrev, const Point3d& ptCurr, const Vector3d& vtDir, double dLinTol, int nLev) const ;
       bool   PrepareHashGrid( void) ;