SmoothingOperator causes log(0.) for logarithmic distances
https://gitlab.mpcdf.mpg.de/ift/NIFTy/blob/master/nifty/operators/smoothing_operator/fft_smoothing_operator.py#L27 https://gitlab.mpcdf.mpg.de/ift/NIFTy/blob/master/nifty/operators/smoothing_operator/fft_smoothing_operator.py#L27
Smoothing should be translationally invariant. Couldn't we just add 1.0 to the distance array?