diff --git a/EXE_GdbGetSurf.cpp b/EXE_GdbGetSurf.cpp
index 5cda347..ac52675 100644
--- a/EXE_GdbGetSurf.cpp
+++ b/EXE_GdbGetSurf.cpp
@@ -21,6 +21,7 @@
 #include "/EgtDev/Include/EXeExecutor.h"
 #include "/EgtDev/Include/EXeConst.h"
 #include "/EgtDev/Include/EGkGeoPoint3d.h"
+#include "/EgtDev/Include/EGkGeoVector3d.h"
 #include "/EgtDev/Include/EGkCurveLine.h"
 #include "/EgtDev/Include/EGkCurveBezier.h"
 #include "/EgtDev/Include/EGkCurveComposite.h"
@@ -1657,6 +1658,38 @@ ExeSurfBezierGetCurveV( int nSurfId, double dU, int nDestGrpId)
    return nNewId ;
 }
 
+//----------------------------------------------------------------------------
+bool
+ExeSurfBezParamsFromPoint( int nSurfId, const Point3d& ptOnSurf, int nDestGrpId)
+{
+   IGeomDB* pGeomDB = GetCurrGeomDB() ;
+   VERIFY_GEOMDB( pGeomDB, GDB_ID_NULL)
+  // recupero la superficie di Bezier
+   const ISurfBezier* pSbz = GetSurfBezier( pGeomDB->GetGeoObj( nSurfId)) ;
+   if ( pSbz == nullptr)
+      return false ;
+   Point3d ptParam, ptBez ;
+   bool bOk = pSbz->UnprojectPoint( ptOnSurf, ptParam, P_INVALID) ;
+   Vector3d vtNorm, vtDerU, vtDerV ;
+   pSbz->GetPointNrmD1D2( ptParam.x, ptParam.y, ISurfBezier::Side::FROM_MINUS, ISurfBezier::Side::FROM_MINUS, ptBez, vtNorm, &vtDerU, &vtDerV) ;
+   if ( ! AreSamePointEpsilon( ptBez, ptOnSurf, 100 * EPS_SMALL))
+      return false ;
+   PtrOwner<IGeoVector3d> vtGeoNorm( CreateGeoVector3d()) ; vtGeoNorm->Set( vtNorm, ptOnSurf) ;
+   int nId = pGeomDB->AddGeoObj( GDB_ID_NULL, nDestGrpId, Release( vtGeoNorm)) ;
+   INTVECTOR vIds ; vIds.push_back( nId) ;
+   ExeSetColor( vIds, Color(255,0,0), false) ;
+   PtrOwner<IGeoVector3d> vtGeoDerU( CreateGeoVector3d()) ; vtGeoDerU->Set( vtDerU, ptOnSurf) ;
+   nId = pGeomDB->AddGeoObj( GDB_ID_NULL, nDestGrpId, Release( vtGeoDerU)) ;
+   vIds.clear() ; vIds.push_back( nId) ;
+   ExeSetColor( vIds, Color(0,128,192), false) ;
+   PtrOwner<IGeoVector3d> vtGeoDerV( CreateGeoVector3d()) ; vtGeoDerV->Set( vtDerV, ptOnSurf) ;
+   nId = pGeomDB->AddGeoObj( GDB_ID_NULL, nDestGrpId, Release( vtGeoDerV)) ;
+   vIds.clear() ; vIds.push_back( nId) ;
+   ExeSetColor( vIds, Color(255,128,0), false) ;
+
+   return bOk ;
+}
+
 //----------------------------------------------------------------------------
 bool
 ExeSurfBezierGetInfo( int nSurfId, int& nDegU, int& nDegV, int& nSpanU, int& nSpanV, bool& bIsRat, bool& bTrimmed)
diff --git a/LUA_GdbGetSurf.cpp b/LUA_GdbGetSurf.cpp
index 9dd7459..7d3c78f 100644
--- a/LUA_GdbGetSurf.cpp
+++ b/LUA_GdbGetSurf.cpp
@@ -1140,6 +1140,25 @@ LuaSurfBezierGetCurveV( lua_State* L)
    return 1 ;
 }
 
+//----------------------------------------------------------------------------
+static int
+LuaSurfBezParamsFromPoint( lua_State* L)
+{
+  // 3 parametri : nSurfId, ptOnSurf, nDestGrp
+   int nSurfId ;
+   LuaCheckParam( L, 1, nSurfId)
+   Point3d ptOnSurf ;
+   LuaCheckParam( L, 2, ptOnSurf)
+   int nDestGrp ;
+   LuaCheckParam( L, 3, nDestGrp)
+   LuaClearStack( L) ;
+  // recupero la curva
+   bool bOk = ExeSurfBezParamsFromPoint( nSurfId, ptOnSurf, nDestGrp) ;
+   LuaSetParam( L) ;
+
+   return 1 ;
+}
+
 //----------------------------------------------------------------------------
 static int
 LuaSurfBezierGetInfo( lua_State* L)
@@ -1312,6 +1331,7 @@ LuaInstallGdbGetSurf( LuaMgr& luaMgr)
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfBezierGetPointNrmD1", LuaSurfBezierGetPointNrmD1) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfBezierGetCurveU", LuaSurfBezierGetCurveU) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfBezierGetCurveV", LuaSurfBezierGetCurveV) ;
+   bOk = bOk && luaMgr.RegisterFunction( "EgtSurfBezParamsFromPoint", LuaSurfBezParamsFromPoint) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfBezierGetInfo", LuaSurfBezierGetInfo) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfBezierGetControlCurveU", LuaSurfBezierGetControlCurveU) ;
    bOk = bOk && luaMgr.RegisterFunction( "EgtSurfBezierGetControlCurveV", LuaSurfBezierGetControlCurveV) ;