levels pyramid (with greedy algorithm) produces oscillating transform

[gdevenyi]

When experimenting with levels, I find the following result:

The image on the left shows that the jacobian generated has an oscillating value on alternate slices, no such oscillations occur if run without levels.

[m-pilia]

Thanks for reporting this! I have seen similar behaviour before, I usually avoid the multi-resolution approach because I observed it can be not stable. On one hand, the interpolation of displacements can be quite coarse. The greedy algorithm uses a 6-point stencil, so error propagation can easily generate that kind of checkboard patters.