diff --git a/EGkGdbConst.h b/EGkGdbConst.h
index 3b53ef6..55864b7 100644
--- a/EGkGdbConst.h
+++ b/EGkGdbConst.h
@@ -42,4 +42,8 @@ enum GdbStatus { GDB_ST_ON =  0,
 //----------------- Costanti materiale oggetti del DB geometrico ---------------
 enum GdbMaterial { GDB_MT_COLOR = -1,
                    GDB_MT_PARENT = 0} ;
-// valori positivi indicano indici nella lista dei materiali (1 based)
\ No newline at end of file
+// valori positivi indicano indici nella lista dei materiali (1 based)
+
+//----------------- Costanti flag di BBox --------------------------------------
+enum BBoxFlag { BBF_NONE = 0,
+                BBF_ONLY_VISIBLE = 1} ;
diff --git a/EGkGdbIterator.h b/EGkGdbIterator.h
index f5c6ddc..39c2afb 100644
--- a/EGkGdbIterator.h
+++ b/EGkGdbIterator.h
@@ -46,6 +46,9 @@ class __declspec( novtable) IGdbIterator
       virtual int  GetId( void) const = 0 ;
       virtual int  GetParentId( void) const = 0 ;
       virtual bool GetGlobFrame( Frame3d& frGlob) const = 0 ;
+      virtual bool GetLocalBBox( BBox3d& b3Loc, int nFlag = BBF_NONE) const = 0 ;
+      virtual bool GetGlobalBBox( BBox3d& b3Glob, int nFlag = BBF_NONE) const = 0 ;
+      virtual bool GetRefBBox( const Frame3d& frRef, BBox3d& b3Ref, int nFlag = BBF_NONE) const = 0 ;
       virtual bool SetLevel( int nLevel) = 0 ;
       virtual bool RevertLevel( void) = 0 ;
       virtual bool GetLevel( int& nLevel) const = 0 ;
diff --git a/EGkGeomDB.h b/EGkGeomDB.h
index f71f861..4aaabb6 100644
--- a/EGkGeomDB.h
+++ b/EGkGeomDB.h
@@ -48,9 +48,9 @@ class __declspec( novtable) IGeomDB
       virtual int  GetGroupObjs( int nId) const = 0 ;
       virtual int  GetParentId( int nId) const = 0 ;
       virtual bool GetGlobFrame( int nId, Frame3d& frGlob) const = 0 ;
-      virtual bool GetLocalBBox( int nId, BBox3d& b3Loc) const = 0 ;
-      virtual bool GetGlobalBBox( int nId, BBox3d& b3Glob) const = 0 ;
-      virtual bool GetRefBBox( int nId, const Frame3d& frRef, BBox3d& b3Ref) const = 0 ;
+      virtual bool GetLocalBBox( int nId, BBox3d& b3Loc, int nFlag = BBF_NONE) const = 0 ;
+      virtual bool GetGlobalBBox( int nId, BBox3d& b3Glob, int nFlag = BBF_NONE) const = 0 ;
+      virtual bool GetRefBBox( int nId, const Frame3d& frRef, BBox3d& b3Ref, int nFlag = BBF_NONE) const = 0 ;
       virtual int  Copy( int nIdSou, int nIdDest, int nParentIdDest) = 0 ;
       virtual int  CopyGlob( int nIdSou, int nIdDest, int nParentIdDest) = 0 ;
       virtual bool Erase( int nId) = 0 ;