diff --git a/EGkTriangle3d.h b/EGkTriangle3d.h
index 9e5e1c8..df05a50 100644
--- a/EGkTriangle3d.h
+++ b/EGkTriangle3d.h
@@ -39,10 +39,11 @@ class Triangle3d
                    return false ;
                 Vector3d vtV = ( ptP[1] - ptP[0]) ^ ( ptP[2] - ptP[0]) ;
                 vtV.Normalize() ;
-                bool bOk = ( vtN.IsZero() || AreSameVectorApprox( vtV, vtN)) ;
-                if ( bOverwrite)
+                if ( vtN.IsZero()  ||  bOverwrite) {
                    vtN = vtV ;
-                return bOk ;
+                   return true ;
+                }
+                return AreSameVectorApprox( vtV, vtN) ;
               }
       bool ToGlob( const Frame3d& frRef)
               { return ( ptP[0].ToGlob( frRef)  &&  ptP[1].ToGlob( frRef)  &&  ptP[2].ToGlob( frRef)) ; }
diff --git a/EGkVolZmap.h b/EGkVolZmap.h
index 9205dc1..8dc430a 100644
--- a/EGkVolZmap.h
+++ b/EGkVolZmap.h
@@ -31,6 +31,8 @@ class __declspec( novtable) IVolZmap : public IGeoObj
       virtual bool CreateFromFlatRegion( const ISurfFlatRegion& Surf, double dDimZ, double dPrec, bool bTriDex) = 0 ;
       virtual bool CreateFromTriMesh( const ISurfTriMesh& Surf, double dPrec, bool bTriDex) = 0 ;
       virtual bool GetAllTriangles( TRIA3DLIST& lstTria) const = 0 ;
+      virtual bool GetBlockTriangles( int nBlock, TRIA3DLIST& lstTria) const = 0 ;
+      virtual bool GetBlockInfo( std::vector<bool> & bModified) const = 0 ;
       virtual bool GetDexelLines( int nDir, int nPos1, int nPos2, POLYLINELIST& lstPL) const = 0 ;
       virtual bool SetTolerances( double dLinTol, double dAngTolDeg = 90) = 0 ;
       virtual bool SetStdTool( const std::string& pToolName, double dH, double dR, double dCornR) = 0 ;