diff --git a/EXE_GdbModifySurf.cpp b/EXE_GdbModifySurf.cpp
index 0d378ba..452e00f 100644
--- a/EXE_GdbModifySurf.cpp
+++ b/EXE_GdbModifySurf.cpp
@@ -491,6 +491,44 @@ ExeSurfFrRotateSimpleNoCollision( int nId1, int nId2, const Point3d& ptCen, doub
    return ( bOk && CAvSimpleSurfFrMove( *pSfr1, *pSfr2L).Rotate(ptCenL, dAngDeg)) ;
 }
 
+//-------------------------------------------------------------------------------
+bool
+ExeCutSurfFrPlane( int nId, const Point3d& ptOn, const Vector3d& vtN, bool bInVsOut, int nRefType)
+{
+   IGeomDB* pGeomDB = GetCurrGeomDB() ;
+   VERIFY_GEOMDB( pGeomDB, false)
+  // recupero la regione piana
+   ISurfFlatRegion* pSfr = GetSurfFlatRegion( pGeomDB->GetGeoObj( nId)) ;
+   bool bOk = ( pSfr != nullptr) ;
+  // recupero il riferimento locale
+   Frame3d frLoc ;
+   bOk = bOk && pGeomDB->GetGlobFrame( nId, frLoc) ;
+  // porto in locale il punto e la normale del piano
+   Point3d ptOnL = GetPointLocal( pGeomDB, ptOn, nRefType, frLoc) ;
+   Vector3d vtNL = GetVectorLocal( pGeomDB, vtN, nRefType, frLoc) ;
+  // calcolo il piano di taglio
+   Plane3d plPlane ;
+   bOk = bOk && plPlane.Set( ptOnL, vtNL) ;
+  // se la parte da conservare è Out, allora inverto il piano
+   if ( ! bInVsOut)
+      plPlane.Invert() ;
+  // eseguo il taglio
+   bOk = bOk && pSfr->Cut( plPlane) ;
+   ExeSetModified() ;
+  // se richiesto, salvo il comando Lua equivalente
+   if ( IsCmdLog()) {
+      string sLua = "EgtCutSurfFrPlane(" + IdToString( nId) + ",{" +
+                                           ToString( ptOn) + "},{" +
+                                           ToString( vtN) + "}," +
+                                           ( bInVsOut ? "true" : "false") + "," +
+                                           RefTypeToString( nRefType) + ")" +
+                    " -- Ok=" + ToString( bOk) ;
+      LOG_INFO( GetCmdLogger(), sLua.c_str()) ;
+   }
+  // restituisco risultato
+   return bOk ;
+}
+
 //-------------------------------------------------------------------------------
 bool
 ExeSurfTmMoveVertex( int nId, int nVert, const Point3d& ptNewVert, int nRefType, bool bUpdate)
diff --git a/LUA_GdbModifySurf.cpp b/LUA_GdbModifySurf.cpp
index ee3bbe0..8b6c177 100644
--- a/LUA_GdbModifySurf.cpp
+++ b/LUA_GdbModifySurf.cpp
@@ -77,11 +77,34 @@ LuaApproxSurf( lua_State* L)
    return 1 ;
 }
 
+//-------------------------------------------------------------------------------
+static int
+LuaCutSurfFrPlane( lua_State* L)
+{
+  // 4 o 5 parametri : SfrId, ptOn, vtN, bInVsOut [, nRefType]
+   int nSfrId ;
+   LuaCheckParam( L, 1, nSfrId)
+   Point3d ptOn ;
+   LuaCheckParam( L, 2, ptOn)
+   Vector3d vtN ;
+   LuaCheckParam( L, 3, vtN)
+   bool bInVsOut ;
+   LuaGetParam( L, 4, bInVsOut) ;
+   int nRefType = RTY_DEFAULT ;
+   LuaGetParam( L, 5, nRefType) ;
+   LuaClearStack( L) ;
+  // taglio la regione con ilpiano
+   bool bOk = ExeCutSurfFrPlane( nSfrId, ptOn, vtN, bInVsOut, nRefType) ;
+  // restituisco il risultato
+   LuaSetParam( L, bOk) ;
+   return 1 ;
+}
+
 //-------------------------------------------------------------------------------
 static int
 LuaSurfFrAdd( lua_State* L)
 {
-  // 2 parametro : Id1, Id2
+  // 2 parametri : Id1, Id2
    int nId1 ;
    LuaCheckParam( L, 1, nId1)
    int nId2 ;
@@ -686,15 +709,16 @@ LuaInstallGdbModifySurf( LuaMgr& luaMgr)
    bOk = bOk && luaMgr.RegisterFunction( "EgtInvertSurf", LuaInvertSurf) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtExplodeSurf", LuaExplodeSurf) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtApproxSurf", LuaApproxSurf) ;
+   bOk = bOk && luaMgr.RegisterFunction( "EgtCutSurfFrPlane", LuaCutSurfFrPlane) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfFrAdd", LuaSurfFrAdd) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfFrSubtract", LuaSurfFrSubtract) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfFrIntersect", LuaSurfFrIntersect) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfFrOffset", LuaSurfFrOffset) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfFrOffsetAdv", LuaSurfFrOffsetAdv) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfFrEraseChunk", LuaSurfFrEraseChunk) ;
-   bOk = bOk && luaMgr.RegisterFunction( "EgtSurfTmMoveVertex", LuaSurfTmMoveVertex) ;  
-   bOk = bOk && luaMgr.RegisterFunction( "EgtSurfTmMoveFacet", LuaSurfTmMoveFacet) ;  
-   bOk = bOk && luaMgr.RegisterFunction( "EgtSurfTmToTriangles", LuaSurfTmToTriangles) ;  
+   bOk = bOk && luaMgr.RegisterFunction( "EgtSurfTmMoveVertex", LuaSurfTmMoveVertex) ;
+   bOk = bOk && luaMgr.RegisterFunction( "EgtSurfTmMoveFacet", LuaSurfTmMoveFacet) ;
+   bOk = bOk && luaMgr.RegisterFunction( "EgtSurfTmToTriangles", LuaSurfTmToTriangles) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfTmRemoveFacet", LuaSurfTmRemoveFacet) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfTmSwapFacets", LuaSurfTmSwapFacets) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfTmRemovePart", LuaSurfTmRemovePart) ;