[Paraview] Compute boundary normals of 2D mesh

[David Nolte]

Dear all,

I'm trying to visualize the normal gradient of a variable along the
boundary of an unstructured 2D mesh.
To compute the normal vectors I tried the following:
- Extract Surface
- Generate Surface Normals

However, the resulting vectors are all n = (0, 0, 1), in the z direction
(the mesh lies in the x-y plane), and not the 2D boundary normals that
I'm looking for.
Is there a way to achieve this with the Paraview filters?

Thanks in advance,
David