diff --git a/EgtGeomKernel.rc b/EgtGeomKernel.rc
index 699e5e0..c90a3d5 100644
Binary files a/EgtGeomKernel.rc and b/EgtGeomKernel.rc differ
diff --git a/IntersSurfTmSurfTm.cpp b/IntersSurfTmSurfTm.cpp
index 4a07e49..1a95d00 100644
--- a/IntersSurfTmSurfTm.cpp
+++ b/IntersSurfTmSurfTm.cpp
@@ -116,7 +116,7 @@ IntersSurfTmSurfTm( const ISurfTriMesh& Stm1, const ISurfTriMesh& Stm2,
                   }
                }
               // se altrimenti sovrapposizione
-               else if ( nRes == ITTT_OVERLAPS) {
+               else if ( nRes == ITTT_OVERLAPS  ||  nRes == ITTT_COUNTER_OVERLAPS) {
                   for ( const auto& Tria : vIttTria) {
                     // verifico se triangolo già inserito
                      bool bFound = false ;
diff --git a/IntersTriaTria.cpp b/IntersTriaTria.cpp
index 03cf31e..8eb8d02 100644
--- a/IntersTriaTria.cpp
+++ b/IntersTriaTria.cpp
@@ -83,8 +83,37 @@ IntersTriaTria( const Triangle3d& trTria1, const Triangle3d& trTria2, Point3d& p
   // se i triangoli sono complanari
    if ( nResPP == IPPT_OVERLAPS  ||
         ((( nVertPos1 == 0  &&  nVertNeg1 == 0)  ||  ( nVertPos2 == 0  &&  nVertNeg2 == 0)) &&
-         ( trTria1.GetN() ^ trTria2.GetN()).SqLen() < 25 * SIN_EPS_ANG_SMALL * SIN_EPS_ANG_SMALL))
-      return IntersCoplanarTriaTria( trTria1, trTria2, vTria) ;
+         ( trTria1.GetN() ^ trTria2.GetN()).SqLen() < 25 * SIN_EPS_ANG_SMALL * SIN_EPS_ANG_SMALL)) {
+     // verifica per triangoli con normali controverse
+      bool bCounter = false ;
+      Triangle3d trMyTria2 = trTria2 ;
+      if ( trTria1.GetN() * trTria2.GetN() < 0) {
+         Point3d ptV0 = trMyTria2.GetP( 0) ;
+         trMyTria2.SetP( 0, trMyTria2.GetP( 1)) ;
+         trMyTria2.SetP( 1, ptV0) ;
+         trMyTria2.Validate() ;
+         bCounter = true ;
+      }
+     // verifica per triangoli coincidenti
+      bool bAreSameTria = ( ( AreSamePointExact( trTria1.GetP( 0), trMyTria2.GetP( 0))  &&
+                              AreSamePointExact( trTria1.GetP( 1), trMyTria2.GetP( 1))  &&
+                              AreSamePointExact( trTria1.GetP( 2), trMyTria2.GetP( 2)))  ||
+                            ( AreSamePointExact( trTria1.GetP( 0), trMyTria2.GetP( 1))  &&
+                              AreSamePointExact( trTria1.GetP( 1), trMyTria2.GetP( 2))  &&
+                              AreSamePointExact( trTria1.GetP( 2), trMyTria2.GetP( 0)))  ||
+                            ( AreSamePointExact( trTria1.GetP( 0), trMyTria2.GetP( 2))  &&
+                              AreSamePointExact( trTria1.GetP( 1), trMyTria2.GetP( 0))  &&
+                              AreSamePointExact( trTria1.GetP( 2), trMyTria2.GetP( 1))))  &&
+                          ( AreSameVectorExact( trTria1.GetN(), trMyTria2.GetN())) ;
+      if ( bAreSameTria) {
+         vTria.emplace_back( trTria1) ;
+         return ( bCounter ? ITTT_COUNTER_OVERLAPS : ITTT_OVERLAPS) ;
+      }
+      if ( ITTT_OVERLAPS == IntersCoplanarTriaTria( trTria1, trMyTria2, vTria)) {
+         return ( bCounter ? ITTT_COUNTER_OVERLAPS : ITTT_OVERLAPS) ;
+      }
+      return ITTT_NO ;
+   }
 
   // limito la linea di intersezione con il primo triangolo
    Point3d ptSt1, ptEn1 ;
diff --git a/SurfTriMeshBooleans.cpp b/SurfTriMeshBooleans.cpp
index 2b199d5..d5b6f8a 100644
--- a/SurfTriMeshBooleans.cpp
+++ b/SurfTriMeshBooleans.cpp
@@ -1339,9 +1339,12 @@ SurfTriMesh::IntersectTriMeshTriangle( SurfTriMesh& Other)
             Point3d ptTempA, ptTempB ;
             int nIntTypeAB = IntersTriaTria( trTriaA, trTriaB, ptTempA, ptTempB, vTriaAB) ;
             if ( nIntTypeAB == ITTT_OVERLAPS) {
-               bool bInvertB = trTriaA.GetN() * trTriaB.GetN() < 0. ;
-               m_vTria[nTA].nTempPart = ( bInvertB ? -2 : 2) ;
-               SurfB.m_vTria[vNearTria[nTB]].nTempPart = ( bInvertB ? - 2 : 2) ;
+               m_vTria[nTA].nTempPart = 2 ;
+               SurfB.m_vTria[vNearTria[nTB]].nTempPart = 2 ;
+            }
+            else if ( nIntTypeAB == ITTT_COUNTER_OVERLAPS) {
+               m_vTria[nTA].nTempPart = -2 ;
+               SurfB.m_vTria[vNearTria[nTB]].nTempPart = -2 ;  
             }
          }
       }
@@ -3663,9 +3666,12 @@ SurfTriMesh::IntersectTriMeshFacets( SurfTriMesh& Other)
             }
             // Se l'intersezeione è corretta e i triangoli sono sovrapposti aggiorno gli indici.
             if ( nIntTypeAB == ITTT_OVERLAPS  &&  bSuccesfullInters) {
-               bool bInvertB = trTriaA.GetN() * trTriaB.GetN() < 0. ;
-               m_vTria[nTA].nTempPart = ( bInvertB ? -2 : 2) ;
-               SurfB.m_vTria[vNearTria[nTB]].nTempPart = ( bInvertB ? - 2 : 2) ;
+               m_vTria[nTA].nTempPart = 2 ;
+               SurfB.m_vTria[vNearTria[nTB]].nTempPart = 2 ;
+            }
+            else if ( nIntTypeAB == ITTT_COUNTER_OVERLAPS  &&  bSuccesfullInters) {
+               m_vTria[nTA].nTempPart = - 2 ;
+               SurfB.m_vTria[vNearTria[nTB]].nTempPart = - 2 ;  
             }
          }
       }