diff --git a/CurveArc.cpp b/CurveArc.cpp
index abd126a..f78f842 100644
--- a/CurveArc.cpp
+++ b/CurveArc.cpp
@@ -25,6 +25,7 @@
 #include "/EgtDev/Include/EGkAngle.h"
 #include "/EgtDev/Include/EGkStringUtils3d.h"
 #include "/EgtDev/Include/EGkUiUnits.h"
+#include "/EgtDev/Include/ENkPolynomialRoots.h"
 #include "/EgtDev/Include/EgtPointerOwner.h"
 #include <new>
 
@@ -701,7 +702,6 @@ CurveArc::GetLocalBBox( BBox3d& b3Loc, int nFlag) const
 {
   // richiamo della funzione generale
    return GetBBox( GLOB_FRM, b3Loc, nFlag) ;
-
 }
 
 //----------------------------------------------------------------------------
@@ -717,115 +717,87 @@ CurveArc::GetBBox( const Frame3d& frRef, BBox3d& b3Ref, int nFlag) const
   // assegno il box nel riferimento
    b3Ref.Reset() ;
 
-  // ricavo il Frame3D solidale all'arco
-   Frame3d frArc; frArc.Set( m_PtCen, m_dAngCenDeg > 0 ? m_VtN : - m_VtN, m_VtS) ;
+  // ricavo il riferimento intrinseco dell'arco
+   Frame3d frArc;
+   frArc.Set( m_PtCen, ( m_dAngCenDeg > 0 ? m_VtN : -m_VtN), m_VtS) ;
 
-  // cordinate nel FrRef dei versori del sistema di riferimento dell'arco
-   Vector3d a = frArc.VersX() ;
-   a.ToGlob( frRef) ;
-   double ax = a.x ;
-   double ay = a.y ;
-   double az = a.z ;
+  // pendenza intrinseca
+   double dPitch = m_dDeltaN * ( m_dAngCenDeg > 0 ? 1 : -1) / abs( m_dAngCenDeg * DEGTORAD) ;
 
-   Vector3d b = frArc.VersY() ;
-   b.ToGlob( frRef) ;
-   double bx = b.x ;
-   double by = b.y ;
-   double bz = b.z ;
-
-   Vector3d c = frArc.VersZ() ;
-   c.ToGlob( frRef) ;
-   double nx = c.x ;
-   double ny = c.y ;
-   double nz = c.z ;
-
-  // vettore degli angoli e dei punti di estremi
-   PNTVECTOR vPoints ;
-   DBLVECTOR vdTheta ;
+  // cordinate nel frRef dei versori del sistema di riferimento dell'arco
+   Vector3d vtXRef = frArc.VersX() ;
+   vtXRef.ToGlob( frRef) ;
+   Vector3d vtYRef = frArc.VersY() ;
+   vtYRef.ToGlob( frRef) ;
+   Vector3d vtZRef = frArc.VersZ() ;
+   vtZRef.ToGlob( frRef) ;
 
   // il punto iniziale e finale sono punti candidati per estremanti
    Point3d ptS, ptE ;
-   GetPointD1D2( 0, FROM_PLUS, ptS) ; if ( ! abs( m_dAngCenDeg - 360) < EPS_SMALL) { GetPointD1D2( 1, FROM_MINUS, ptE) ; }
-   vPoints.push_back( ptS) ; if ( ! abs( m_dAngCenDeg - 360) < EPS_SMALL) { vPoints.push_back( ptE) ; }
+   GetStartPoint( ptS) ;
+   ptS.ToGlob( frRef) ;
+   b3Ref.Add( ptS) ;
+   GetEndPoint( ptE) ;
+   ptE.ToGlob( frRef) ;
+   b3Ref.Add( ptE) ;
 
-  // angolo al centro, raggio e parametro Q
-   double dAngCenRad = m_dAngCenDeg * DEGTORAD ;
-   ptE.ToLoc( frArc) ; ptS.ToLoc( frArc) ;
-   double Q = ( ptE.z - ptS.z) / abs( dAngCenRad) ;
-   double dRad = m_dRad ;
+  // vettore degli angoli dei punti candidati estremi
+   DBLVECTOR vdTheta ;
 
-   if ( abs( Q) < EPS_SMALL) {
-      if ( abs( ax) > EPS_SMALL) {
-         vdTheta.push_back( atan( bx / ax)) ;
-         vdTheta.push_back( vdTheta.back() > 0 ? vdTheta.back() + PIGRECO : vdTheta.back() - PIGRECO) ;
+   // arco piatto
+   if ( abs( dPitch) < EPS_SMALL) {
+      double dAngXDeg = atan2( vtYRef.x, vtXRef.x) * RADTODEG ;
+      bool bAngXSmall = (abs( dAngXDeg) <= EPS_ANG_ZERO) ;
+      if ( ! bAngXSmall) {
+         vdTheta.push_back( dAngXDeg) ;
+         vdTheta.push_back( dAngXDeg + ANG_STRAIGHT) ;
       }
-      if ( abs( ay) > EPS_SMALL) {
-         vdTheta.push_back( atan( by / ay)) ;
-         vdTheta.push_back( vdTheta.back() > 0 ? vdTheta.back() + PIGRECO : vdTheta.back() - PIGRECO) ;
+      double dAngYDeg = atan2( vtYRef.y, vtXRef.y) * RADTODEG ;
+      bool bAngYSmall = (abs( dAngYDeg) <= EPS_ANG_ZERO) ;
+      if ( ! bAngYSmall) {
+         vdTheta.push_back( dAngYDeg) ;
+         vdTheta.push_back( dAngYDeg + ANG_STRAIGHT) ;
       }
-      if ( abs( az) > EPS_SMALL) {
-         vdTheta.push_back( atan( bz / az)) ;
-         vdTheta.push_back( vdTheta.back() > 0 ? vdTheta.back() + PIGRECO : vdTheta.back() - PIGRECO) ;
+      double dAngZDeg = atan2( vtYRef.z, vtXRef.z) * RADTODEG ;
+      bool bAngZSmall = (abs( dAngZDeg) <= EPS_ANG_ZERO) ;
+      if ( ! bAngZSmall) {
+         vdTheta.push_back( dAngZDeg) ;
+         vdTheta.push_back( dAngZDeg + ANG_STRAIGHT) ;
       }
+      if ( bAngXSmall  ||  bAngYSmall  || bAngZSmall)
+         vdTheta.push_back( ANG_STRAIGHT) ;
    }
+  // altrimenti arco di elica
    else {
-
-      vector<double> Va ; Va.push_back( ax) ; Va.push_back( ay) ; Va.push_back( az) ;
-      vector<double> Vb ; Vb.push_back( bx) ; Vb.push_back( by) ; Vb.push_back( bz) ;
-      vector<double> Vn ; Vn.push_back( nx) ; Vn.push_back( ny) ; Vn.push_back( nz) ;
-
-      for ( int i = 0 ; i < 3 ; i++) {
-         double delta = dRad * dRad * Va[i] * Va[i] - Q * Q * Vn[i] * Vn[i] + Vb[i] * Vb[i] * dRad * dRad ;
-         if ( delta > 0) {
-            double t1 = ( dRad * Va[i] + sqrt( delta)) / ( Q * Vn[i] - dRad * Vb[i]) ;
-            if ( abs( 1 - t1 * t1) > EPS_SMALL) {
-               vdTheta.push_back( atan( 2 * t1 / (1 - t1 * t1))) ;
-               vdTheta.push_back(vdTheta.back() > 0 ? vdTheta.back() + PIGRECO : vdTheta.back() - PIGRECO);
-            }
-            double t2 = ( dRad * Va[i] - sqrt( delta)) / ( Q * Vn[i] - dRad * Vb[i]) ;
-            if ( abs( 1 - t2 * t2) > EPS_SMALL){
-               vdTheta.push_back( atan( 2 * t2 / ( 1 - t2 * t2))) ;
-               vdTheta.push_back( vdTheta.back() > 0 ? vdTheta.back() + PIGRECO : vdTheta.back() - PIGRECO) ;
+      for ( int i = 0 ; i < 3 ; ++ i) {
+         DBLVECTOR vdPoly{ m_dRad * vtYRef.v[i] + dPitch * vtZRef.v[i],
+                           - 2 * m_dRad * vtXRef.v[i],
+                           - m_dRad * vtYRef.v[i] + dPitch * vtZRef.v[i]} ;
+         DBLVECTOR vdRoot ;
+         int nRoot = PolynomialRoots( 2, vdPoly, vdRoot) ;
+         for ( int i = 0 ; i < nRoot ; ++ i) {
+            double dAngDeg = atan2( 2 * vdRoot[i], (1 - vdRoot[i] * vdRoot[i])) * RADTODEG ;
+            if ( abs( dAngDeg) > EPS_ANG_ZERO) {
+               vdTheta.push_back( dAngDeg) ;
+               vdTheta.push_back( dAngDeg + ANG_STRAIGHT) ;
             }
+            else
+               vdTheta.push_back( ANG_STRAIGHT) ;
          }
       }
    }
 
-   vdTheta.push_back( PIGRECO) ;
-   vdTheta.push_back( PIGRECO / 2) ;
-   vdTheta.push_back( 3 * PIGRECO / 2) ;
-
-   for ( int i = 0 ; i < vdTheta.size() ; i++) {
-      double dTheta = vdTheta[i] > 0 ? vdTheta[i] : 2 * PIGRECO + vdTheta[i] ;
-      if ( dTheta < abs( dAngCenRad)) {
-         Point3d pt ;
-         GetPointD1D2( dTheta / ( abs( dAngCenRad)), FROM_MINUS, pt) ;
-         vPoints.push_back( pt) ;
+  // verifica degli angoli sull'arco ed eventuale considerazione dei punti
+   for ( int i = 0 ; i < int( vdTheta.size()) ; ++ i) {
+      double dTheta = ( vdTheta[i] > 0 ? vdTheta[i] : vdTheta[i] + ANG_FULL) ;
+      if ( dTheta < abs( m_dAngCenDeg)) {
+         Point3d ptP ;
+         GetPointD1D2( dTheta / ( abs( m_dAngCenDeg)), FROM_MINUS, ptP) ;
+         ptP.ToGlob( frRef) ;
+         b3Ref.Add( ptP) ;
       }
    }
-
-   for (int i = 0; i < vPoints.size(); i++) {
-      vPoints[i].ToGlob( frRef) ;
-      b3Ref.Add( vPoints[i]) ;
-   }
    
-   return true ;
-
-  /*
-   double dLinTol = LIN_TOL_APPROX ;
-   double dAngTolDeg = ANG_TOL_APPROX_DEG ;
-   if ( ( nFlag & BBF_EXACT) != 0)
-      dLinTol = LIN_TOL_MIN ;
-   ArcApproxer aAppr( dLinTol, dAngTolDeg, false, *this) ;
-   double  dU ;
-   Point3d ptPos ;
-   while ( aAppr.GetPoint( dU, ptPos)) {
-      ptPos.ToGlob( frRef) ;
-      b3Ref.Add( ptPos) ;
-   }
-
-   */
-
   // se c'è estrusione, devo tenerne conto
    if ( ! m_VtExtr.IsSmall()  &&  abs( m_dThick) > EPS_SMALL) {
       Vector3d vtFrExtr = m_VtExtr ;
diff --git a/CurveAux.cpp b/CurveAux.cpp
index 0c401aa..239b8df 100644
--- a/CurveAux.cpp
+++ b/CurveAux.cpp
@@ -30,9 +30,8 @@ using namespace std ;
 bool
 IsClosed( const ICurve& crvC)
 {
-   Point3d ptStart ;
-   Point3d ptEnd ;
-   return ( crvC.GetStartPoint( ptStart)  &&  crvC.GetEndPoint( ptEnd)  &&   AreSamePointApprox( ptStart, ptEnd)) ;
+   Point3d ptStart, ptEnd ;
+   return ( crvC.GetStartPoint( ptStart)  &&  crvC.GetEndPoint( ptEnd)  &&  AreSamePointApprox( ptStart, ptEnd)) ;
 }
 
 //----------------------------------------------------------------------------
diff --git a/SurfTriMeshBooleans.cpp b/SurfTriMeshBooleans.cpp
index 6a4f967..b8a27ad 100644
--- a/SurfTriMeshBooleans.cpp
+++ b/SurfTriMeshBooleans.cpp
@@ -694,7 +694,7 @@ SurfTriMesh::RetriangulationForBooleanOperation( CHAINMAP& LoopLines, TRIA3DVECT
         // Elimino loop interni non validi
          bool bDouble = true ;
          for ( int nInnLoop = 0 ; nInnLoop < int( vInnerLoop.size()) ; ++ nInnLoop) {
-            if ( int( cvClosedChain[vInnerLoop[nInnLoop]].size()) > 2) {
+            if ( cvClosedChain[vInnerLoop[nInnLoop]].size() > 2) {
                bDouble = false ;
                break ;
             }
@@ -820,6 +820,7 @@ SurfTriMesh::RetriangulationForBooleanOperation( CHAINMAP& LoopLines, TRIA3DVECT
                   }
                }
             }
+
            // Divido i loop che si autointercettano
             int nInitialLoopNum = int( vPolygons.size()) ;
             for ( int nL = 1 ; nL < nInitialLoopNum ; ++ nL) {
@@ -868,8 +869,8 @@ SurfTriMesh::RetriangulationForBooleanOperation( CHAINMAP& LoopLines, TRIA3DVECT
                      itSt2 = LoopPointList.emplace( itEn2, vAddingPointWithOrder[nPi]) ;
                   }
                }
+
               // Spezzo i loop autointersecantesi
-               
                POLYLINEVECTOR vAuxPolygons ;
                vAuxPolygons.emplace_back( vPolygons[nL]) ;
 
@@ -917,7 +918,7 @@ SurfTriMesh::RetriangulationForBooleanOperation( CHAINMAP& LoopLines, TRIA3DVECT
                }
                bool bReplaced = false ;
                for ( int nl = 0 ; nl < int( vAuxPolygons.size()) ; ++ nl) {
-                  if ( true/*vAuxPolygons.GetAreaXY(double& dArea)*/) {
+                  if ( true) {
                      if ( ! bReplaced) {
                         vPolygons[nL].Clear() ;
                         Point3d ptP ;