diff --git a/SurfTriMeshBooleans.cpp b/SurfTriMeshBooleans.cpp
index 0e341bf..43805db 100644
--- a/SurfTriMeshBooleans.cpp
+++ b/SurfTriMeshBooleans.cpp
@@ -4544,24 +4544,30 @@ SurfTriMesh::ItersectTriMeshFacets( SurfTriMesh& Other)
                            itFacetB->second[nPieceNumB].nPiecePart = nPartIndex;
                         }
                      }
-                     else if ( nResPP == IPPT_YES  &&  abs(plPlaneA.GetDist() - plPlaneB.GetDist()) < EPS_SMALL &&  AreSameVectorApprox( plPlaneA.GetVersN(), plPlaneB.GetVersN())) {
-                        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) ;
-                           // 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;
+                     else if (nResPP == IPPT_YES) {
+                        Point3d ptCentroidA, ptCentroidB ;
+                        RegionA.GetCentroid( ptCentroidA) ;
+                        RegionB.GetCentroid( ptCentroidB) ;
+                        if ( AreSameVectorApprox( 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);
+                              // 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;
+                              }
                            }
                         }
                      }
@@ -4597,27 +4603,33 @@ SurfTriMesh::ItersectTriMeshFacets( SurfTriMesh& Other)
                            SurfB.m_vTria[nTB].nTempPart = nPartIndex ;
                      }
                   }
-                  else if ( nResPP == IPPT_YES    &&  abs(plPlaneA.GetDist() - plPlaneB.GetDist()) < EPS_SMALL &&  AreSameVectorApprox( plPlaneA.GetVersN(), plPlaneB.GetVersN())) {
-                     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) ;
-                        // 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 ;
+                  else if ( nResPP == IPPT_YES) {
+                     Point3d ptCentroidA, ptCentroidB ;
+                     RegionA.GetCentroid( ptCentroidA) ;
+                     RegionB.GetCentroid( ptCentroidB) ;
+                     if (AreSameVectorApprox(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);
+                           // 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;
+                           }
                         }
                      }
                   }
@@ -4685,27 +4697,33 @@ SurfTriMesh::ItersectTriMeshFacets( SurfTriMesh& Other)
                         itFacetB->second[nPieceNumB].nPiecePart = nPartIndex ;
                      }
                   }
-                  else if ( nResPP == IPPT_YES    &&  abs(plPlaneA.GetDist() - plPlaneB.GetDist()) < EPS_SMALL &&  AreSameVectorApprox( plPlaneA.GetVersN(), plPlaneB.GetVersN())) {
-                     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) ;
-                        // Assegno indice di parte ai triangoli di A e ai pezzi di 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 ;
-                           itFacetB->second[nPieceNumB].nPiecePart = nPartIndex ;
+                  else if ( nResPP == IPPT_YES) {
+                     Point3d ptCentroidA, ptCentroidB ;
+                     RegionA.GetCentroid( ptCentroidA) ;
+                     RegionB.GetCentroid( ptCentroidB) ;
+                     if ( AreSameVectorApprox( 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) ;
+                           // Assegno indice di parte ai triangoli di A e ai pezzi di 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 ;
+                              itFacetB->second[nPieceNumB].nPiecePart = nPartIndex ;
+                           }
                         }
                      }
                   }
@@ -4744,30 +4762,38 @@ SurfTriMesh::ItersectTriMeshFacets( SurfTriMesh& Other)
                         SurfB.m_vTria[nTB].nTempPart = nPartIndex ;
                   }
                }
-               else if ( nResPP == IPPT_YES    &&  abs(plPlaneA.GetDist() - plPlaneB.GetDist()) < EPS_SMALL &&  AreSameVectorApprox( plPlaneA.GetVersN(), plPlaneB.GetVersN())) {
-                  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) ;
-                     // 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 ;
+               else if (nResPP == IPPT_YES) {
+                  Point3d ptCentroidA, ptCentroidB ;
+                  RegionA.GetCentroid( ptCentroidA) ;
+                  RegionB.GetCentroid( ptCentroidB) ;
+                  bool bVecOk = AreSameVectorApprox(plPlaneA.GetVersN(), plPlaneB.GetVersN());
+                  double dOk = abs((ptCentroidB - ptCentroidA) * plPlaneA.GetVersN());
+                  if ( AreSameVectorApprox( 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);
+                        // 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;
+                        }
                      }
                   }
                }