diff --git a/EgtGeomKernel.rc b/EgtGeomKernel.rc
index 42bbfb4..8139089 100644
Binary files a/EgtGeomKernel.rc and b/EgtGeomKernel.rc differ
diff --git a/VolZmap.cpp b/VolZmap.cpp
index 5bf2b56..f31e17d 100644
--- a/VolZmap.cpp
+++ b/VolZmap.cpp
@@ -1188,8 +1188,8 @@ VolZmap::ClonePart( int nPart) const
          -- nMinIndJ[nMap] ;
       if ( nMaxIndJ[nMap] < int( m_nNy[nMap]) - 1)
          ++ nMaxIndJ[nMap] ;
-      pVolume->m_nNx[nMap] = nMaxIndI[nMap] - nMinIndI[nMap] + 1 ;
-      pVolume->m_nNy[nMap] = nMaxIndJ[nMap] - nMinIndJ[nMap] + 1 ;
+      pVolume->m_nNx[nMap] = max( 0, nMaxIndI[nMap] - nMinIndI[nMap] + 1) ;
+      pVolume->m_nNy[nMap] = max( 0, nMaxIndJ[nMap] - nMinIndJ[nMap] + 1) ;
       pVolume->m_nDim[nMap] = pVolume->m_nNx[nMap] * pVolume->m_nNy[nMap] ;
       pVolume->m_Values[nMap].resize( pVolume->m_nDim[nMap]) ;
    }
diff --git a/VolZmapGraphics.cpp b/VolZmapGraphics.cpp
index a379ed9..24c127f 100644
--- a/VolZmapGraphics.cpp
+++ b/VolZmapGraphics.cpp
@@ -2216,8 +2216,8 @@ VolZmap::ExtMarchingCubes( int nBlock, VoxelContainer& vVox) const
          double dYMax = ( nDexMaxJ + 0.5) * m_dStep ;
          double dZMax = ( nDexMaxK + 0.5) * m_dStep ;                                                                                     
         // Determino colore dei triangoli       
-         int nFaceInfGrade = m_Values[1][nDexMinK * m_nNx[1] + nDexMinJ][0].nToolMin ;
-         int nFaceSupGrade = m_Values[1][nDexMinK * m_nNx[1] + nDexMinJ][0].nToolMax ;
+         int nFaceInfGrade = ( ! m_Values[1].empty() ? m_Values[1][nDexMinK * m_nNx[1] + nDexMinJ][0].nToolMin : 0) ;
+         int nFaceSupGrade = ( ! m_Values[1].empty() ? m_Values[1][nDexMinK * m_nNx[1] + nDexMinJ][0].nToolMax : 0) ;
         // Piano di coordinata x inferiore: versore normale rivolto come X-                            
          if ( nBlockIJK[0] == 0) {                  
             Triangle3dEx trTria1, trTria2 ;
@@ -2255,8 +2255,8 @@ VolZmap::ExtMarchingCubes( int nBlock, VoxelContainer& vVox) const
          double dXMax = ( nDexMaxI + 0.5) * m_dStep ;
          double dZMax = ( nDexMaxK + 0.5) * m_dStep ;                                                     
         // Determino colore dei triangoli        
-         int nFaceInfGrade = m_Values[2][nDexMinI * m_nNx[2] + nDexMinK][0].nToolMin ;
-         int nFaceSupGrade = m_Values[2][nDexMinI * m_nNx[2] + nDexMinK][0].nToolMax ;              
+         int nFaceInfGrade = ( ! m_Values[2].empty() ? m_Values[2][nDexMinI * m_nNx[2] + nDexMinK][0].nToolMin : 0) ;
+         int nFaceSupGrade = ( ! m_Values[2].empty() ? m_Values[2][nDexMinI * m_nNx[2] + nDexMinK][0].nToolMax : 0) ;              
         // Piano di coordinata y inferiore: versore normale rivolto come Y-       
          if ( nBlockIJK[1] == 0) {               
             Triangle3dEx trTria1, trTria2 ;  
@@ -4024,7 +4024,7 @@ VolZmap::GetFirstVoxIJK( int& i, int& j, int& k) const
       bool bNotEmpty = false ;
       for ( nj = 0 ; nj < 2 ; ++ nj) {
          int nDex = nj * int( m_nNx[0]) + ni ;      
-         if ( m_Values[0][nDex].size() > 0) {
+         if ( ! m_Values[0].empty()  &&  m_Values[0][nDex].size() > 0) {
             bNotEmpty = true ;
             break ;    
          }            
@@ -4037,7 +4037,7 @@ VolZmap::GetFirstVoxIJK( int& i, int& j, int& k) const
       bool bNotEmpty = false ;
       for ( mj = 0 ; mj < 2 ; ++ mj) {
          int nDex = mj * int( m_nNx[1]) + mi ;
-         if ( m_Values[1][nDex].size() > 0) {
+         if ( ! m_Values[1].empty()  &&  m_Values[1][nDex].size() > 0) {
             bNotEmpty = true ;
             break ;
          }           
@@ -4067,7 +4067,7 @@ VolZmap::GetLastVoxIJK( int& i, int& j, int& k) const
       bool bNotEmpty = false ;
       for ( nj = int( m_nNy[0]) - 1 ; nj > int( m_nNy[0]) - 3 ; -- nj) {
          int nDex = nj * int( m_nNx[0]) + ni ;
-         if ( m_Values[0][nDex].size() > 0) {
+         if ( ! m_Values[0].empty()  &&  m_Values[0][nDex].size() > 0) {
             bNotEmpty = true ;
             break ; 
          }        
@@ -4080,7 +4080,7 @@ VolZmap::GetLastVoxIJK( int& i, int& j, int& k) const
       bool bNotEmpty = false ;
       for ( mj = int( m_nNy[1]) - 1 ; mj > int( m_nNy[1]) - 3 ; -- mj) {
          int nDex = mj * int( m_nNx[1]) + mi ;        
-         if ( m_Values[1][nDex].size() > 0) {
+         if ( ! m_Values[1].empty()  &&  m_Values[1][nDex].size() > 0) {
             bNotEmpty = true ;
             break ;    
          }