diff --git a/StmFromTriangleSoup.cpp b/StmFromTriangleSoup.cpp
index 08db0c7..8c55a74 100644
--- a/StmFromTriangleSoup.cpp
+++ b/StmFromTriangleSoup.cpp
@@ -99,14 +99,14 @@ StmFromTriangleSoup::AddTriangle( const Point3d& ptP0, const Point3d& ptP1, cons
 
 //----------------------------------------------------------------------------
 int
-StmFromTriangleSoup::AddVertex( const Point3d& ptP)
+StmFromTriangleSoup::AddVertex( const Point3d& ptP, const double dU, const double dV)
 {
   // verifico se già presente
    int nId ;
    if ( m_VertGrid.Find( ptP, 2 * EPS_SMALL, nId))
       return nId ;
   // aggiungo il vertice
-   if ( ( nId = m_pSTM->AddVertex( ptP)) == SVT_NULL)
+   if ( ( nId = m_pSTM->AddVertex( ptP, dU, dV)) == SVT_NULL)
       return SVT_NULL ;
    m_VertGrid.InsertPoint( ptP, nId) ;
    return nId ;
diff --git a/SurfBezier.cpp b/SurfBezier.cpp
index 6c7588a..bb2e591 100644
--- a/SurfBezier.cpp
+++ b/SurfBezier.cpp
@@ -1524,7 +1524,7 @@ SurfBezier::GetAuxSurf( void) const
       Triangulate Tri ;
       if ( ! Tri.Make( vPL, vPnt, vTria))
          return nullptr ;
-         
+     
      // porto i punti in 3d
       PNTVECTOR vPnt3d ;
       for ( int i = 0 ; i < int( vPnt.size()) ; ++ i) {
diff --git a/SurfTriMesh.cpp b/SurfTriMesh.cpp
index 76ad9e9..d171748 100644
--- a/SurfTriMesh.cpp
+++ b/SurfTriMesh.cpp
@@ -107,7 +107,7 @@ SurfTriMesh::Clear( void)
 
 //----------------------------------------------------------------------------
 int
-SurfTriMesh::AddVertex( const Point3d& ptVert)
+SurfTriMesh::AddVertex( const Point3d& ptVert, const double dU, const double dV)
 {
   // imposto ricalcolo
    m_nStatus = TO_VERIFY ;
@@ -118,7 +118,11 @@ SurfTriMesh::AddVertex( const Point3d& ptVert)
    try { m_vVert.emplace_back( ptVert) ;}
    catch(...) { return SVT_NULL ;}
   // ne determino l'indice
-   return int( m_vVert.size() - 1) ;
+   int nId = int( m_vVert.size() - 1) ;
+  // aggiugo le coordinate corrispondenti allo spazio parametrico
+   m_vVert[nId].dU = dU ;
+   m_vVert[nId].dV = dV ;
+   return nId ;
 }
 
 //----------------------------------------------------------------------------
@@ -475,6 +479,19 @@ SurfTriMesh::GetVertex( int nId, Point3d& ptP) const
    return true ;
 }
 
+//----------------------------------------------------------------------------
+bool
+SurfTriMesh::GetVertexParam( int nId, double& dU, double& dV) const
+{
+   // verifico esistenza del vertice
+   if ( nId < 0  ||  nId >= GetVertexSize()  ||  m_vVert[nId].nIdTria == SVT_DEL)
+      return false ;
+   // recupero i dati
+   dU = m_vVert[nId].dU ;
+   dV = m_vVert[nId].dV ;
+   return true ;
+}
+
 //----------------------------------------------------------------------------
 int
 SurfTriMesh::GetFirstVertex( Point3d& ptP) const
@@ -482,6 +499,13 @@ SurfTriMesh::GetFirstVertex( Point3d& ptP) const
    return GetNextVertex( SVT_NULL, ptP) ;
 }
 
+//----------------------------------------------------------------------------
+int
+SurfTriMesh::GetFirstVertexParam( int nId, double& dU, double& dV) const
+{
+   return GetNextVertexParam( SVT_NULL, dU, dV) ;
+}
+
 //----------------------------------------------------------------------------
 int
 SurfTriMesh::GetNextVertex( int nId, Point3d& ptP) const
@@ -499,6 +523,24 @@ SurfTriMesh::GetNextVertex( int nId, Point3d& ptP) const
    return nId ;
 }
 
+//----------------------------------------------------------------------------
+int
+SurfTriMesh::GetNextVertexParam( int nId, double& dU, double& dV) const
+{
+   // cerco il primo successivo valido
+   do {
+      nId ++ ;
+   } while ( nId < GetVertexSize()  &&  m_vVert[nId].nIdTria == SVT_DEL) ;
+   // se oltrepassata fine
+   if ( nId >= GetVertexSize())
+      return SVT_NULL ;
+   // recupero i dati
+   dU = m_vVert[nId].dU ;
+   dV = m_vVert[nId].dV ;
+   // ritorno indice triangolo corrente
+   return nId ;
+}
+
 //----------------------------------------------------------------------------
 bool
 SurfTriMesh::GetTriangle( int nId, int nIdVert[3]) const
diff --git a/SurfTriMesh.h b/SurfTriMesh.h
index 6ae2946..9f8c8d1 100644
--- a/SurfTriMesh.h
+++ b/SurfTriMesh.h
@@ -28,11 +28,15 @@ class SurfFlatRegion ;
 class StmVert
 {
    public :
-      StmVert( void) : ptP(), nIdTria( SVT_NULL), nFlag( 0), nTemp( 0) {}
-      StmVert( const Point3d& ptQ) : ptP( ptQ), nIdTria( SVT_NULL), nFlag( 0), nTemp( 0) {}
-      StmVert( const Point3d& ptQ, int nIdT, int nF) : ptP( ptQ), nIdTria( nIdT), nFlag( nF), nTemp( 0) {}
+      StmVert( void) : ptP(), nIdTria( SVT_NULL), nFlag( 0), nTemp( 0), dU( -1), dV( -1) {}
+      StmVert( const Point3d& ptQ) : ptP( ptQ), nIdTria( SVT_NULL), nFlag( 0), nTemp( 0), dU( -1), dV( -1) {}
+      StmVert( const Point3d& ptQ, int nIdT, int nF) : ptP( ptQ), nIdTria( nIdT), nFlag( nF), nTemp( 0), dU( -1), dV( -1) {}
    public :
       Point3d ptP ;
+      double   dU ;  // parametro riferito alle coordinate del punto nello spazio parametrico ( nSpanU x nSpanV)
+                     // della sup di Bezier   // -1 se non definito
+      double   dV ;  // parametro riferito alle coordinate del punto nello spazio parametrico ( nSpanU x nSpanV)
+                     // della sup di Bezier   // -1 se non definito
       int     nIdTria ;
       int     nFlag ;
       mutable int nTemp ;
@@ -215,7 +219,7 @@ class SurfTriMesh : public ISurfTriMesh, public IGeoObjRW
               { m_dSmoothAng = std::max( dSmoothAngDeg, EPS_ANG_SMALL) ;
                 m_dCosSmAng = cos( m_dSmoothAng * DEGTORAD) ;
                 m_OGrMgr.Reset() ; }
-      int  AddVertex( const Point3d& ptVert) override ;
+      int  AddVertex( const Point3d& ptVert, const double dU = -1 , const double dV = -1) override ;
       bool MoveVertex( int nInd, const Point3d& ptNewVert) override ;
       int  AddTriangle( const int nIdVert[3], int nTFlag = 0) override ; 
       bool RemoveTriangle( int nId) override ;
@@ -244,8 +248,11 @@ class SurfTriMesh : public ISurfTriMesh, public IGeoObjRW
       double GetSmoothAngle( void) const override
               { return m_dSmoothAng ; }
       bool GetVertex( int nId, Point3d& ptP) const override ;
+      bool GetVertexParam( int nId, double& dU, double& dV) const override ;
       int  GetFirstVertex( Point3d& ptP) const override ;
+      int  GetFirstVertexParam( int nId, double& dU, double& dV) const override ;
       int  GetNextVertex( int nId, Point3d& ptP) const override ;
+      int  GetNextVertexParam( int nId, double& dU, double& dV) const override ;
       bool GetTriangle( int nId, int nIdVert[3]) const override ;
       int  GetFirstTriangle( int nIdVert[3]) const override ; 
       int  GetNextTriangle( int nId, int nIdVert[3]) const override ;