diff --git a/EXE_Scene.cpp b/EXE_Scene.cpp
index 30f6e59..b365c71 100644
--- a/EXE_Scene.cpp
+++ b/EXE_Scene.cpp
@@ -16,6 +16,7 @@
 #include "EXE.h"
 #include "EXE_Macro.h"
 #include "DllGraphics.h"
+#include "/EgtDev/Include/EGkSurfBezier.h"
 #include "/EgtDev/Include/EXeExecutor.h"
 #include "/EgtDev/Include/EXeConst.h"
 #include "/EgtDev/Include/EgtStringConverter.h"
@@ -435,6 +436,8 @@ ExeGetShowCurveDirection( void)
 static bool
 MyResetGroupObjGraphics( IGeomDB* pGDB, int nGroupId)
 {
+   if ( pGDB == nullptr)
+      return false ;
    int nEntId = pGDB->GetFirstInGroup( nGroupId) ;
    while ( nEntId != GDB_ID_NULL) {
       if ( pGDB->GetGdbType( nEntId) == GDB_TY_GROUP) {
@@ -461,13 +464,12 @@ ExeSetShowTriaAdv( bool bAdvanced, bool bRedraw)
      // imposto il nuovo stato
       pScene->SetShowTriaAdvanced( bAdvanced) ;
      // forzo ricalcolo della grafica di tutti gli oggetti
-      IGeomDB* pGDB = pScene->GetGeomDB() ;
-      if ( pGDB != nullptr)
-         MyResetGroupObjGraphics( pGDB, GDB_ID_ROOT) ;
+      if ( ! MyResetGroupObjGraphics( pScene->GetGeomDB(), GDB_ID_ROOT))
+         return false ;
    }
    if ( bRedraw)
       pScene->RedrawWindow() ;
-   return TRUE ;
+   return true ;
 }
 
 //-----------------------------------------------------------------------------
@@ -480,17 +482,50 @@ ExeGetShowTriaAdv( void)
    return pScene->GetShowTriaAdvanced() ;
 }
 
+//-------------------------------------------------------------------------------
+bool
+ExeSetShowSurfBezierTol( double dLinTol, bool bRedraw) 
+{
+   IEGrScene* pScene = GetCurrScene() ;
+   VERIFY_SCENE( pScene, false)
+  // se diverso, imposto il nuovo valore
+   if ( abs( GetSurfBezierAuxSurfTol() - dLinTol) > 10 * EPS_SMALL) {
+     // imposto il nuovo valore di approssimazione
+      SetSurfBezierAuxSurfTol( dLinTol) ;
+     // forzo ricalcolo della grafica di tutti gli oggetti
+      if ( ! MyResetGroupObjGraphics( pScene->GetGeomDB(), GDB_ID_ROOT))
+         return false ;
+   }
+   if ( bRedraw)
+      pScene->RedrawWindow() ;
+   return true ;
+}
+
+//-----------------------------------------------------------------------------
+double
+ExeGetShowSurfBezierTol( void)
+{
+  // recupero il valore
+   return GetSurfBezierAuxSurfTol() ;
+}
+
 //-----------------------------------------------------------------------------
 bool
 ExeSetShowZmap( int nMode, bool bRedraw)
 {
    IEGrScene* pScene = GetCurrScene() ;
    VERIFY_SCENE( pScene, false)
-  // imposto stato
-   pScene->SetShowZmap( nMode) ;
+  // se cambiato, imposto il nuovo stato
+   if ( pScene->GetShowZmap() != nMode) {
+     // imposto il nuovo stato
+      pScene->SetShowZmap( nMode) ;
+     // forzo ricalcolo della grafica di tutti gli oggetti
+      if ( ! MyResetGroupObjGraphics( pScene->GetGeomDB(), GDB_ID_ROOT))
+         return false ;
+   }
    if ( bRedraw)
       pScene->RedrawWindow() ;
-   return TRUE ;
+   return true ;
 }
 
 //-----------------------------------------------------------------------------
@@ -498,7 +533,7 @@ int
 ExeGetShowZmap( void)
 {
    IEGrScene* pScene = GetCurrScene() ;
-   VERIFY_SCENE( pScene, false)
+   VERIFY_SCENE( pScene, -1)
   // recupero lo stato
    return pScene->GetShowZmap() ;
 }