diff --git a/EGkGeoCollection.h b/EGkGeoCollection.h
index 30d6c60..b480210 100644
--- a/EGkGeoCollection.h
+++ b/EGkGeoCollection.h
@@ -20,8 +20,9 @@
 
 //----------------------------------------------------------------------------
 // Raccolte di Point3d
-typedef std::vector<Point3d>  PNTVECTOR ;   // vettore di punti
-typedef std::list<Point3d>    PNTLIST ;     // lista di punti
+typedef std::vector<Point3d>   PNTVECTOR ;   // vettore di punti
+typedef std::list<Point3d>     PNTLIST ;     // lista di punti
+typedef std::vector<PNTVECTOR> PNTMATRIX ;   // matrice di punti
 
 //----------------------------------------------------------------------------
 // Raccolte di coppie Point3d,dU
diff --git a/EGkGeoConst.h b/EGkGeoConst.h
index a2fb01f..78adb38 100644
--- a/EGkGeoConst.h
+++ b/EGkGeoConst.h
@@ -1,13 +1,13 @@
 //----------------------------------------------------------------------------
-//  EgalTech 2013-2013
+//  EgalTech 2013-2019
 //----------------------------------------------------------------------------
-// File : EgkGeoConst.h           Data : 20.11.13          Versione : 1.3a1
+// File : EgkGeoConst.h           Data : 23.11.19          Versione : 2.1k5
 // Contenuto : Costanti generali per calcoli geometrici.       
 //
 //
 //
 // Modifiche : 04.01.12 DS Creazione modulo.
-//
+//             23.11.19 DS Aggiunta costante EPS_TRIA_H.
 //
 //----------------------------------------------------------------------------
 
@@ -21,10 +21,12 @@ const double ONEINCH = 25.4 ;
 
 // epsilon per lunghezze, versori e parametri
 const double EPS_SMALL = 1e-3 ;
+const double EPS_TRIA_H = 1e-6 ;
 const double EPS_ZERO  = 1e-8 ;
 const double EPS_PARAM = 1e-8 ;
 const double SPAN_PARAM = 1.0 ;    // intervallo di curva o superficie semplici
 const double SQ_EPS_SMALL = EPS_SMALL * EPS_SMALL ;
+const double SQ_EPS_TRIA_H = EPS_TRIA_H * EPS_TRIA_H ;
 const double SQ_EPS_ZERO = EPS_ZERO * EPS_ZERO ;
 
 // infinito per lunghezze
diff --git a/EGkTriangle3d.h b/EGkTriangle3d.h
index c4dba47..5e76ded 100644
--- a/EGkTriangle3d.h
+++ b/EGkTriangle3d.h
@@ -51,22 +51,36 @@ class Triangle3d
       bool Validate( bool bOverwrite = false)
               { if ( AreSamePointApprox( m_ptP[0], m_ptP[1])  ||  AreSamePointApprox( m_ptP[0], m_ptP[2]))
                    return false ;
-                Vector3d vtV = ( m_ptP[1] - m_ptP[0]) ^ ( m_ptP[2] - m_ptP[0]) ;
-                vtV.Normalize( EPS_ZERO) ;
+                Vector3d vtV1 = m_ptP[1] - m_ptP[0] ;
+                Vector3d vtV2 = m_ptP[2] - m_ptP[1] ;
+                Vector3d vtN = vtV1 ^ vtV2 ;
+                double dSqN = vtN.SqLen() ;
+                if ( dSqN < SQ_EPS_ZERO)
+                   return false ;
+                if ( dSqN < SQ_EPS_TRIA_H * std::max( { vtV1.SqLen(), vtV2.SqLen(), ( vtV1 + vtV2).SqLen()}))
+                   return false ;
+                vtN /= sqrt( dSqN) ;
                 if ( m_vtN.IsSmall()  ||  bOverwrite) {
-                   m_vtN = vtV ;
+                   m_vtN = vtN ;
                    return true ;
                 }
-                return AreSameVectorApprox( vtV, m_vtN) ;
+                return AreSameVectorApprox( vtN, m_vtN) ;
               }
       bool IsValid( void) const
               { if ( AreSamePointApprox( m_ptP[0], m_ptP[1])  ||  AreSamePointApprox( m_ptP[0], m_ptP[2]))
                    return false ;
                 if ( m_vtN.IsSmall())
                    return false ;
-                Vector3d vtV = ( m_ptP[1] - m_ptP[0]) ^ ( m_ptP[2] - m_ptP[0]) ;
-                vtV.Normalize( EPS_ZERO) ;
-                return AreSameVectorApprox( vtV, m_vtN) ;
+                Vector3d vtV1 = m_ptP[1] - m_ptP[0] ;
+                Vector3d vtV2 = m_ptP[2] - m_ptP[1] ;
+                Vector3d vtN = vtV1 ^ vtV2 ;
+                double dSqN = vtN.SqLen() ;
+                if ( dSqN < SQ_EPS_ZERO)
+                   return false ;
+                if ( dSqN < SQ_EPS_TRIA_H * std::max( { vtV1.SqLen(), vtV2.SqLen(), ( vtV1 + vtV2).SqLen()}))
+                   return false ;
+                vtN /= sqrt( dSqN) ;
+                return AreSameVectorApprox( vtN, m_vtN) ;
               }
       void Translate( const Vector3d& vtMove)
               { m_ptP[0].Translate( vtMove) ;