[Graphics:lll1gr2.gif][Graphics:lll1gr1.gif]

[Graphics:lll1gr2.gif][Graphics:lll1gr3.gif]

[Graphics:lll1gr2.gif][Graphics:lll1gr4.gif]
[Graphics:lll1gr2.gif][Graphics:lll1gr5.gif]

[Graphics:lll1gr2.gif][Graphics:lll1gr6.gif]
[Graphics:lll1gr2.gif][Graphics:lll1gr7.gif]
[Graphics:lll1gr2.gif][Graphics:lll1gr8.gif]
The black curve is the seam curve. The red and green curves are the partial derivatives of the seam; they show the locations of the turning points.

The topology of this curve was computed in 45 seconds. Most of the time is spent finding the (three) turning points.

For a certain parametrization of a line-line bisector surface, the parametric domain [0,1]x[0,1] corresponds to exactly the portions of the curve which could possibly be part of the medial axis.