diff --git a/SurfTriMesh.cpp b/SurfTriMesh.cpp
index 2fdf8e2..1a80f28 100644
--- a/SurfTriMesh.cpp
+++ b/SurfTriMesh.cpp
@@ -4415,6 +4415,35 @@ SurfTriMesh::ClonePart( int nPart) const
    return Release( pSurfTM) ;
 }
 
+//----------------------------------------------------------------------------
+bool 
+SurfTriMesh::GetPartAndShellFromFacet( int nFacet, int& nPart, int& nShell) const
+{
+   // l'indice della faccia deve essere nei limiti
+   if ( nFacet < 0  ||  nFacet >= int( m_vFacet.size()))
+      return false ;
+
+   // mi assicuro che siano calcolate il numero di parti e di shell
+   int nParts = GetPartCount() ;
+
+   int nTria = m_vFacet[nFacet] ;
+   nShell = m_vTria[nTria].nShell ;
+
+   // scopro in quale part è la shell
+   int nPartTemp = 0 ;
+   nPart = - 1 ;
+   while ( nPartTemp < nParts  &&  nPart == - 1) {
+      for ( int i : m_vPart[nPartTemp].vShell) {
+         if ( i == nShell) {
+            nPart = nPartTemp ;
+            break ;
+         }
+      }
+      ++nPartTemp ;
+   }
+   return true ;
+}
+
 //----------------------------------------------------------------------------
 bool
 SurfTriMesh::ResetTFlags( void)
diff --git a/SurfTriMesh.h b/SurfTriMesh.h
index 3ab9637..44b1fa2 100644
--- a/SurfTriMesh.h
+++ b/SurfTriMesh.h
@@ -347,6 +347,7 @@ class SurfTriMesh : public ISurfTriMesh, public IGeoObjRW
       bool GetPartVolume( int nPart, double& dVolume) const override ;
       bool GetPartLoops( int nPart, POLYLINEVECTOR& vPL) const override ;
       SurfTriMesh* ClonePart( int nPart) const override ;
+      bool GetPartAndShellFromFacet( int nFacet, int& nPart, int& nShell) const override ;
       bool SetTFlag( int nId, int nTFlag) override ;
       bool GetTFlag( int nId, int& nFlag) const override ;
       int  GetMaxTFlag( void) const override