0029591: Improvements in the class BRepOffset_Tool

- Add the flag ExtensionMode in the method BRepOffset_Tool::EnLargeFace, defining the mode of extension of the surface of the face. Old behavior is to be remained the default one.

- Fix wrong building of extended face on a closed surface. Now, if the face is closed in U direction (like cylinder) but the seam edge is shifted from 0 position, the resulting extended face has properly connected seam edge.

- Add new public static method BRepTools::DetectClosedness(), which checks whether a face is closed in U and V directions.

src/BRepTools/BRepTools.cxx

@@ -25,6 +25,7 @@
 #include <BRepTools.hxx>
 #include <BRepTools_MapOfVertexPnt2d.hxx>
 #include <BRepTools_ShapeSet.hxx>
+#include <BRepAdaptor_Surface.hxx>
 #include <ElCLib.hxx>
 #include <Geom2d_Curve.hxx>
 #include <Geom2dAdaptor_Curve.hxx>
@@ -64,6 +65,27 @@
 #include <TopTools_SequenceOfShape.hxx>
 #include <GeomLib_CheckCurveOnSurface.hxx>
 #include <errno.h>
+
+
+//=======================================================================
+//function : IsPCurveUiso
+//purpose  : 
+//=======================================================================
+
+static Standard_Boolean IsPCurveUiso(const Handle(Geom2d_Curve)& thePCurve,
+                                     Standard_Real theFirstPar,
+                                     Standard_Real theLastPar)
+{
+  gp_Pnt2d FirstP2d = thePCurve->Value(theFirstPar);
+  gp_Pnt2d LastP2d  = thePCurve->Value(theLastPar);
+
+  Standard_Real DeltaU = Abs(FirstP2d.X() - LastP2d.X());
+  Standard_Real DeltaV = Abs(FirstP2d.Y() - LastP2d.Y());
+
+  return (DeltaU < DeltaV);
+}
+
+
 //=======================================================================
 //function : UVBounds
 //purpose  : 
@@ -994,6 +1016,43 @@ Standard_Boolean BRepTools::IsReallyClosed(const TopoDS_Edge& E,
   return nbocc == 2;
 }
 
+//=======================================================================
+//function : DetectClosedness
+//purpose  : 
+//=======================================================================
+
+void BRepTools::DetectClosedness(const TopoDS_Face& theFace,
+                                 Standard_Boolean&  theUclosed,
+                                 Standard_Boolean&  theVclosed)
+{
+  theUclosed = theVclosed = Standard_False;
+  
+  BRepAdaptor_Surface BAsurf(theFace, Standard_False);
+  Standard_Boolean IsSurfUclosed = BAsurf.IsUClosed();
+  Standard_Boolean IsSurfVclosed = BAsurf.IsVClosed();
+  if (!IsSurfUclosed && !IsSurfVclosed)
+    return;
+  
+  TopExp_Explorer Explo(theFace, TopAbs_EDGE);
+  for (; Explo.More(); Explo.Next())
+  {
+    const TopoDS_Edge& anEdge = TopoDS::Edge(Explo.Current());
+    if (BRepTools::IsReallyClosed(anEdge, theFace))
+    {
+      Standard_Real fpar, lpar;
+      Handle(Geom2d_Curve) aPCurve = BRep_Tool::CurveOnSurface(anEdge, theFace, fpar, lpar);
+      Standard_Boolean IsUiso = IsPCurveUiso(aPCurve, fpar, lpar);
+      if (IsSurfUclosed && IsUiso)
+        theUclosed = Standard_True;
+      if (IsSurfVclosed && !IsUiso)
+        theVclosed = Standard_True;
+      
+      if (theUclosed && theVclosed)
+        break;
+    }
+  }
+}
+
 //=======================================================================
 //function : EvalAndUpdateTol
 //purpose  : 

src/BRepTools/BRepTools.hxx

@@ -186,6 +186,11 @@ public:
   //! the face <F> before calling BRep_Tool::IsClosed.
   Standard_EXPORT static Standard_Boolean IsReallyClosed (const TopoDS_Edge& E, const TopoDS_Face& F);
   
+  //! Detect closedness of face in U and V directions
+  Standard_EXPORT static void DetectClosedness (const TopoDS_Face& theFace,
+                                                Standard_Boolean&  theUclosed,
+                                                Standard_Boolean&  theVclosed);
+  
   //! Dumps the topological structure and the geometry
   //! of <Sh> on the stream <S>.
   Standard_EXPORT static void Dump (const TopoDS_Shape& Sh, Standard_OStream& S);