In this picture, you can see that some of the displacements at the front surface are non-zero, but the displacements at the remaining five surfaces are zero (since these were not measured).

I want to compute the gradient of the displacement vector, but it does not make much sense to do this on the 3d mesh, since the gradient is dominated by the jump to the surfaces with the non-zero values.

That said, is there a way to extract the surface (containing the measured values), thus, having a 2d mesh, and compute the gradient on this surface? The surface is characterized by the points with z-coordinate zero.

After the slice filter, the contour plot is a surface with a displacement in x- and y-direction.

What I want is to get the displacement as a vector in 2d rather than in 3d by simply “forgetting” about the z-coordinate. So the gradient has 4 components.
Can I do this in paraview?