private void AdjustPeriodic(Face face2, ICurve2D curveOnFace2, GeoPoint leaveFace1)
        {
            if (!face2.Surface.IsUPeriodic && !face2.Surface.IsVPeriodic)
            {
                return;
            }
            double uperiod = 0.0, vperiod = 0.0;

            if (face2.Surface.IsUPeriodic)
            {
                uperiod = face2.Surface.UPeriod;
            }
            if (face2.Surface.IsVPeriodic)
            {
                vperiod = face2.Surface.VPeriod;
            }
            GeoPoint2D pos = face2.Surface.PositionOf(leaveFace1);

            if (!face2.area.Contains(pos, true))
            {   // dieser Punkt muss eigentlich in Area anthalten sein, er kann höchstens um die Periode verschoben sein
                bool          found = false;
                CompoundShape tst   = face2.area.Expand((uperiod + vperiod) / 100);
                if (tst.Contains(pos, true))
                {
                    found = true;
                }
                if (!found && uperiod > 0.0)
                {
                    if (tst.Contains(pos + uperiod * GeoVector2D.XAxis, true))
                    {
                        pos   = pos + uperiod * GeoVector2D.XAxis;
                        found = true;
                    }
                    if (!found && tst.Contains(pos - uperiod * GeoVector2D.XAxis, true))
                    {
                        pos   = pos - uperiod * GeoVector2D.XAxis;
                        found = true;
                    }
                }
                if (!found && vperiod > 0.0)
                {
                    if (tst.Contains(pos + vperiod * GeoVector2D.YAxis, true))
                    {
                        pos   = pos + vperiod * GeoVector2D.YAxis;
                        found = true;
                    }
                    if (!found && tst.Contains(pos - vperiod * GeoVector2D.YAxis, true))
                    {
                        pos   = pos - vperiod * GeoVector2D.YAxis;
                        found = true;
                    }
                }
            }
            // jetzt die Kurve so verschieben, dass der Punkt draufliegt
            double du = 0.0, dv = 0.0;
            double dist = curveOnFace2.MinDistance(pos);

            if (uperiod > 0.0)
            {
                double d = curveOnFace2.MinDistance(pos + uperiod * GeoVector2D.XAxis);
                if (d < dist)
                {
                    du   = -uperiod;
                    dist = d;
                }
                d = curveOnFace2.MinDistance(pos - uperiod * GeoVector2D.XAxis);
                if (d < dist)
                {
                    du   = uperiod;
                    dist = d;
                }
            }
            if (vperiod > 0.0)
            {
                double d = curveOnFace2.Distance(pos + vperiod * GeoVector2D.YAxis);
                if (d < dist)
                {
                    dv   = -vperiod;
                    dist = d;
                }
                d = curveOnFace2.Distance(pos - vperiod * GeoVector2D.YAxis);
                if (d < dist)
                {
                    dv   = vperiod;
                    dist = d;
                }
            }
            if (du != 0.0 || dv != 0.0)
            {
                curveOnFace2.Move(du, dv);
            }
        }