diff --git a/SurfTriMeshBooleans.cpp b/SurfTriMeshBooleans.cpp
index a646862..ca7b68e 100644
--- a/SurfTriMeshBooleans.cpp
+++ b/SurfTriMeshBooleans.cpp
@@ -4532,41 +4532,47 @@ SurfTriMesh::ItersectTriMeshFacets( SurfTriMesh& Other)
                      Point3d ptL ; Vector3d vtL ;
                      int nResPP = IntersPlanePlane( plPlaneA, plPlaneB, ptL, vtL) ;
                      if ( /*nResPP == IPPT_NO ||*/ nResPP == IPPT_OVERLAPS) {
+                        // Se necessario inverto la regione B per eseguire l'intersezione.
+                        if ( plPlaneA.GetVersN() * plPlaneB.GetVersN() < - EPS_SMALL)
+                           RegionB.Invert() ;
                         SurfFlatRegion frIntersRegion = RegionA ;
                         frIntersRegion.Intersect( RegionB) ;
                         double dIntersRegArea ;
                         frIntersRegion.GetArea( dIntersRegArea) ;
                         // Assegno indice di parte ai pezzi.
                         if ( dIntersRegArea > EPS_SMALL) {
-                           bool bCodirectedNorm = RegionA.GetNormVersor() * RegionB.GetNormVersor() > 0;
+                           bool bCodirectedNorm = RegionA.GetNormVersor() * RegionB.GetNormVersor() > 0 ;
                            int nPartIndex = bCodirectedNorm ? 2 : - 2 ;
-                           itFacetA->second[nPieceNumA].nPiecePart = nPartIndex;
-                           itFacetB->second[nPieceNumB].nPiecePart = nPartIndex;
+                           itFacetA->second[nPieceNumA].nPiecePart = nPartIndex ;
+                           itFacetB->second[nPieceNumB].nPiecePart = nPartIndex ;
                         }
                      }
-                     else if (nResPP == IPPT_YES) {
+                     else if ( nResPP == IPPT_YES) {
                         Point3d ptCentroidA, ptCentroidB ;
                         RegionA.GetCentroid( ptCentroidA) ;
                         RegionB.GetCentroid( ptCentroidB) ;
                         if ( AreSameOrOppositeVectorApprox( plPlaneA.GetVersN(), plPlaneB.GetVersN())  &&
                              abs( ( ptCentroidB - ptCentroidA) * plPlaneA.GetVersN()) < EPS_SMALL) {
-                           BBox3d b3Box, b3BoxB;
-                           RegionA.GetLocalBBox(b3Box);
-                           RegionB.GetLocalBBox(b3BoxB);
-                           b3Box.Add(b3BoxB);
-                           b3Box.Expand(10);
-                           INTDBLVECTOR vInters;
-                           if (!IntersLineBox(ptL, vtL, 100., b3Box, vInters, false) || int(vInters.size()) < 2) {
-                              SurfFlatRegion frIntersRegion = RegionA;
-                                 frIntersRegion.Intersect(RegionB);
-                                 double dIntersRegArea;
-                                 frIntersRegion.GetArea(dIntersRegArea);
+                           BBox3d b3Box, b3BoxB ;
+                           RegionA.GetLocalBBox( b3Box) ;
+                           RegionB.GetLocalBBox( b3BoxB) ;
+                           b3Box.Add( b3BoxB) ;
+                           b3Box.Expand( 10) ;
+                           INTDBLVECTOR vInters ;
+                           if ( ! IntersLineBox( ptL, vtL, 100., b3Box, vInters, false)  ||  int( vInters.size()) < 2) {
+                              // Se necessario inverto la regione B per eseguire l'intersezione.
+                              if ( plPlaneA.GetVersN() * plPlaneB.GetVersN() < - EPS_SMALL)
+                                 RegionB.Invert() ;
+                              SurfFlatRegion frIntersRegion = RegionA ;
+                                 frIntersRegion.Intersect( RegionB) ;
+                                 double dIntersRegArea ;
+                                 frIntersRegion.GetArea( dIntersRegArea) ;
                               // Assegno indice di parte ai pezzi.
-                              if (dIntersRegArea > EPS_SMALL) {
-                                 bool bCodirectedNorm = RegionA.GetNormVersor() * RegionB.GetNormVersor() > 0;
-                                 int nPartIndex = bCodirectedNorm ? 2 : -2;
-                                 itFacetA->second[nPieceNumA].nPiecePart = nPartIndex;
-                                 itFacetB->second[nPieceNumB].nPiecePart = nPartIndex;
+                              if ( dIntersRegArea > EPS_SMALL) {
+                                 bool bCodirectedNorm = RegionA.GetNormVersor() * RegionB.GetNormVersor() > 0 ;
+                                 int nPartIndex = bCodirectedNorm ? 2 : - 2 ;
+                                 itFacetA->second[nPieceNumA].nPiecePart = nPartIndex ;
+                                 itFacetB->second[nPieceNumB].nPiecePart = nPartIndex ;
                               }
                            }
                         }
@@ -4588,6 +4594,9 @@ SurfTriMesh::ItersectTriMeshFacets( SurfTriMesh& Other)
                   Point3d ptL ; Vector3d vtL ;
                   int nResPP = IntersPlanePlane( plPlaneA, plPlaneB, ptL, vtL) ;
                   if ( /*nResPP == IPPT_NO  ||*/  nResPP == IPPT_OVERLAPS) {
+                     // Se necessario inverto la regione B per eseguire l'intersezione.
+                     if ( plPlaneA.GetVersN() * plPlaneB.GetVersN() < - EPS_SMALL)
+                        RegionB.Invert() ;
                      SurfFlatRegion frIntersRegion = RegionA ;
                      frIntersRegion.Intersect( RegionB) ;
                      double dIntersRegArea ;
@@ -4608,27 +4617,30 @@ SurfTriMesh::ItersectTriMeshFacets( SurfTriMesh& Other)
                      RegionA.GetCentroid( ptCentroidA) ;
                      RegionB.GetCentroid( ptCentroidB) ;
                      if ( AreSameOrOppositeVectorApprox(plPlaneA.GetVersN(), plPlaneB.GetVersN()) &&
-                        abs((ptCentroidB - ptCentroidA) * plPlaneA.GetVersN()) < EPS_SMALL) {
-                        BBox3d b3Box, b3BoxB;
-                        RegionA.GetLocalBBox(b3Box);
-                        RegionB.GetLocalBBox(b3BoxB);
-                        b3Box.Add(b3BoxB);
-                        b3Box.Expand(10);
-                        INTDBLVECTOR vInters;
-                        if (!IntersLineBox(ptL, vtL, 100., b3Box, vInters, false) || int(vInters.size()) < 2) {
-                           SurfFlatRegion frIntersRegion = RegionA;
-                              frIntersRegion.Intersect(RegionB);
-                              double dIntersRegArea;
-                           frIntersRegion.GetArea(dIntersRegArea);
+                          abs( ( ptCentroidB - ptCentroidA) * plPlaneA.GetVersN()) < EPS_SMALL) {
+                        BBox3d b3Box, b3BoxB ;
+                        RegionA.GetLocalBBox( b3Box) ;
+                        RegionB.GetLocalBBox( b3BoxB) ;
+                        b3Box.Add( b3BoxB) ;
+                        b3Box.Expand( 10) ;
+                        INTDBLVECTOR vInters ;
+                        if ( ! IntersLineBox( ptL, vtL, 100., b3Box, vInters, false)  ||  int( vInters.size()) < 2) {
+                           // Se necessario inverto la regione B per eseguire l'intersezione.
+                           if ( plPlaneA.GetVersN() * plPlaneB.GetVersN() < - EPS_SMALL)
+                              RegionB.Invert() ;
+                           SurfFlatRegion frIntersRegion = RegionA ;
+                           frIntersRegion.Intersect( RegionB) ;
+                           double dIntersRegArea ;
+                           frIntersRegion.GetArea( dIntersRegArea) ;
                            // Assegno indice di parte al pezzo di faccia A e ai triangoli della faccia B.
-                           if (dIntersRegArea > EPS_SMALL) {
-                              bool bCodirectedNorm = RegionA.GetNormVersor() * RegionB.GetNormVersor() > 0;
-                              int nPartIndex = bCodirectedNorm ? 2 : -2;
-                              itFacetA->second[nPieceNumA].nPiecePart = nPartIndex;
-                              INTVECTOR vTB;
-                              SurfB.GetAllTriaInFacet(nFB, vTB);
-                              for (int& nTB : vTB)
-                                 SurfB.m_vTria[nTB].nTempPart = nPartIndex;
+                           if ( dIntersRegArea > EPS_SMALL) {
+                              bool bCodirectedNorm = RegionA.GetNormVersor() * RegionB.GetNormVersor() > 0 ;
+                              int nPartIndex = bCodirectedNorm ? 2 : - 2 ;
+                              itFacetA->second[nPieceNumA].nPiecePart = nPartIndex ;
+                              INTVECTOR vTB ;
+                              SurfB.GetAllTriaInFacet( nFB, vTB) ;
+                              for ( int& nTB : vTB)
+                                 SurfB.m_vTria[nTB].nTempPart = nPartIndex ;
                            }
                         }
                      }
@@ -4686,6 +4698,9 @@ SurfTriMesh::ItersectTriMeshFacets( SurfTriMesh& Other)
                   Point3d ptL ; Vector3d vtL ;
                   int nResPP = IntersPlanePlane( plPlaneA, plPlaneB, ptL, vtL) ;
                   if ( /*nResPP == IPPT_NO  ||*/  nResPP == IPPT_OVERLAPS) {
+                     // Se necessario inverto la regione B per eseguire l'intersezione.
+                     if ( plPlaneA.GetVersN() * plPlaneB.GetVersN() < - EPS_SMALL)
+                        RegionB.Invert() ;
                      SurfFlatRegion frIntersRegion = RegionA ;
                      frIntersRegion.Intersect( RegionB) ;
                      double dIntersRegArea ;
@@ -4714,6 +4729,9 @@ SurfTriMesh::ItersectTriMeshFacets( SurfTriMesh& Other)
                         b3Box.Expand( 10) ;
                         INTDBLVECTOR vInters;
                         if ( ! IntersLineBox( ptL, vtL, 100., b3Box, vInters, false)  ||  int( vInters.size()) < 2) {
+                           // Se necessario inverto la regione B per eseguire l'intersezione.
+                           if ( plPlaneA.GetVersN() * plPlaneB.GetVersN() < - EPS_SMALL)
+                              RegionB.Invert() ;
                            SurfFlatRegion frIntersRegion = RegionA ;
                            frIntersRegion.Intersect( RegionB) ;
                            double dIntersRegArea ;
@@ -4748,6 +4766,9 @@ SurfTriMesh::ItersectTriMeshFacets( SurfTriMesh& Other)
                Point3d ptL ; Vector3d vtL ;
                int nResPP = IntersPlanePlane( plPlaneA, plPlaneB, ptL, vtL) ;
                if ( /*nResPP == IPPT_NO  ||*/  nResPP == IPPT_OVERLAPS) {
+                  // Se necessario inverto la regione B per eseguire l'intersezione.
+                  if ( plPlaneA.GetVersN() * plPlaneB.GetVersN() < - EPS_SMALL)
+                     RegionB.Invert() ;
                   SurfFlatRegion frIntersRegion = RegionA ;
                   frIntersRegion.Intersect( RegionB) ;
                   double dIntersRegArea ;
@@ -4766,35 +4787,38 @@ SurfTriMesh::ItersectTriMeshFacets( SurfTriMesh& Other)
                         SurfB.m_vTria[nTB].nTempPart = nPartIndex ;
                   }
                }
-               else if (nResPP == IPPT_YES) {
+               else if ( nResPP == IPPT_YES) {
                   Point3d ptCentroidA, ptCentroidB ;
                   RegionA.GetCentroid( ptCentroidA) ;
                   RegionB.GetCentroid( ptCentroidB) ;
                   if ( AreSameOrOppositeVectorApprox( plPlaneA.GetVersN(), plPlaneB.GetVersN())  &&
-                     abs( ( ptCentroidB - ptCentroidA) * plPlaneA.GetVersN()) < EPS_SMALL) {
-                     BBox3d b3Box, b3BoxB;
-                     RegionA.GetLocalBBox(b3Box);
-                     RegionB.GetLocalBBox(b3BoxB);
-                     b3Box.Add(b3BoxB);
-                     b3Box.Expand(10);
-                     INTDBLVECTOR vInters;
-                     if (!IntersLineBox(ptL, vtL, 100., b3Box, vInters, false) || int(vInters.size()) < 2) {
-                        SurfFlatRegion frIntersRegion = RegionA;
-                        frIntersRegion.Intersect(RegionB);
-                        double dIntersRegArea;
-                        frIntersRegion.GetArea(dIntersRegArea);
+                       abs( ( ptCentroidB - ptCentroidA) * plPlaneA.GetVersN()) < EPS_SMALL) {
+                     BBox3d b3Box, b3BoxB ;
+                     RegionA.GetLocalBBox( b3Box) ;
+                     RegionB.GetLocalBBox( b3BoxB) ;
+                     b3Box.Add( b3BoxB) ;
+                     b3Box.Expand( 10) ;
+                     INTDBLVECTOR vInters ;
+                     if ( ! IntersLineBox( ptL, vtL, 100., b3Box, vInters, false)  ||  int( vInters.size()) < 2) {
+                        // Se necessario inverto la regione B per eseguire l'intersezione.
+                        if ( plPlaneA.GetVersN() * plPlaneB.GetVersN() < - EPS_SMALL)
+                           RegionB.Invert() ;
+                        SurfFlatRegion frIntersRegion = RegionA ;
+                        frIntersRegion.Intersect( RegionB) ;
+                        double dIntersRegArea ;
+                        frIntersRegion.GetArea( dIntersRegArea) ;
                         // Assegno indice di parte al pezzo di faccia A e ai triangoli della faccia B.
-                        if (dIntersRegArea > EPS_SMALL) {
-                           bool bCodirectedNorm = RegionA.GetNormVersor() * RegionB.GetNormVersor() > 0;
-                           int nPartIndex = bCodirectedNorm ? 2 : -2;
-                           INTVECTOR vTA;
-                           GetAllTriaInFacet(nFA, vTA);
-                           for (int& nTA : vTA)
-                              m_vTria[nTA].nTempPart = nPartIndex;
-                           INTVECTOR vTB;
-                           SurfB.GetAllTriaInFacet(nFB, vTB);
-                           for (int& nTB : vTB)
-                              SurfB.m_vTria[nTB].nTempPart = nPartIndex;
+                        if ( dIntersRegArea > EPS_SMALL) {
+                           bool bCodirectedNorm = RegionA.GetNormVersor() * RegionB.GetNormVersor() > 0 ;
+                           int nPartIndex = bCodirectedNorm ? 2 : - 2 ;
+                           INTVECTOR vTA ;
+                           GetAllTriaInFacet( nFA, vTA) ;
+                           for ( int& nTA : vTA)
+                              m_vTria[nTA].nTempPart = nPartIndex ;
+                           INTVECTOR vTB ;
+                           SurfB.GetAllTriaInFacet( nFB, vTB) ;
+                           for ( int& nTB : vTB)
+                              SurfB.m_vTria[nTB].nTempPart = nPartIndex ;
                         }
                      }
                   }