As far as I understand, current THX::Interpolate() makes interpolation according to the neighbouring bins values. Would it be possible to make another version of Interpolate() that takes nearest non-empty bins instead of neighbouring bins? I guess, this may be not possible for TH, because it does not provide information if the bin is empty or not, but perhaps it would be possible for TProfile/2D/3D?
I know that you can direct me to TGraph2D::Interpolate() 
But there is no TGraph3D, so 3D values, stored in a TH3 with many empty bins, cannot be easily interpolated.