[vtkusers] vtkThinPlateSplineTransform propogation

[Dean Inglis]

I have a ruled surface composed of a spline curve defined in
an x-y plane and extruded along the z axis.  I have a corresponding
ruled surface which is essentially the same surface but ironed flat;
a rectangular plane, hence, the corresponding curve is a straight line.
  The points are regularly spaced along the
curve and parallel curves along the z axis are equally spaced.
The number of points (can be tens to hundreds) along any x-y cut through 
either surface
(ie a curve or line) is the same.  I want the transform that relates 
coordinates of points
forming the flattened surface to those of the curved surface.  If I use 
vtkThinPlateSplineTransform for
relating points in the bottom line of the flat surface to the corresponding 
points
in the curved suface, the transform is fast and works perfectly, but as I 
traverse upward
to other areas of the surface the correspondance diminishes.  If I include
additional points, as in from a pair of middle curves and a pair of top 
curves,
the correspondance is better, but diminishes in between those regions, and, 
furthermore,
the number of points significantly increases, slowing the transformation 
calculations drastically.
Is there a way to propogate the transformation from only one set of curve 
pairs?
I have looked at the code in vtkThinPlateSplineTransform but I have no idea 
where
to begin making modifications.

thanks,
Dean