OK, upon further investigation, the interpolation is seriously cracked.

Initially I played around with the starting data set in the SVG,
and then when the interpolated patches started wigging out, I went back and
moved the data points around a bit and moved the camera to look at the spline in
z, y, and z.   It _looked_ ok.

The following are interpolated splines for:

#declare DataSet = array [5]{
array[10]{<-40, 0, 0>, <0,0,0>, <0,0,0>, <-30, 0, 0>, <0,0,0>, <0,0,0>, <-20, 0,
0>, <0,0,0>, <0,0,0>, <-10, 0, 0>},
array[10]{<10, 0, 0>, <0,0,0>, <0,0,0>, <20, 0, 0>, <0,0,0>, <0,0,0>, <30, 0,
0>, <0,0,0>, <0,0,0>, <40, 0, 0>},

array[10]{<20, 20, 0>, <0,0,0>, <0,0,0>, <30, 30, 0>, <0,0,0>, <0,0,0>, <40, 20,
0>, <0,0,0>, <0,0,0>, <50, 25, 0>}

array[10]{<-10, 5, 0>, <0,0,0>, <0,0,0>, <-20, 5, 0>, <0,0,0>, <0,0,0>, <-30, 5,
0>, <0,0,0>, <0,0,0>, <-40, 5, 0>},
array[10]{<40, 5, 0>, <0,0,0>, <0,0,0>, <30, 5, 0>, <0,0,0>, <0,0,0>, <20, 5,
0>, <0,0,0>, <0,0,0>, <10, 5, 0>}
};

As you can see, I took the top 2 splines and just reordered the data from
beginning to end (and shifted y by 5).   Not looking good.
Someone please page Jerome.  LeForgeron is needed with his mathematical / c++
cape, to bend this Bezier back in line!  Er, I mean curve!  No, wait - line.
:|

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