Single contour curve constructor

  TSweep3D(   const TGCurve& contour,
              const TGCurve3D& trajectory,
              const TGPoint3D& initialContourXDirection,
              const TGCurve& scaling = GetEmptySweepCurve,
              const TGCurve& twist = GetEmptySweepCurve,
              TGrafBundle* adoptBundle = NIL );