[vtkusers] Computing curvature of a surface

[Jan Ehrhardt]

hi folks,

I have the following problem: I want to register two polygonal surfaces
using nonlinear transformations.
I have implemented an algorithm similar to andresens and nielsen
"geometry constrained diffusion".
This works like ICP but for nonlinear transformations.
Actually, I match the nearest points on the two surfaces.
The idea is not only to use the spatial distance but also the normal
vektors and curvature of the points
to identify corresponding points.
The normals caan I compute using vtkPolyDataNormals, but how to compute
the curvature of the surface points?
Concrete:
I have an polydata surface (no associated image or scalar values!). 
How can I compute the curvature for each point (triangle vertex) from
the polydata ?
Curvature means min and max curvature and /or gaussian curvature.

Regards and many thanks for ANY help,

Jan