grid size is fixed when mapOnFly = false

[sonjageorgievska]

Li told me to note down this, so that everyone knows: if the training uses already mapped features in 3D, then the network will use the resolution as it is in the hdf5 files.

[NicoRenaud]

Yes it should be better documented then :) Or do you suggest to change that somehow ?

[CunliangGeng]

@LilySnow Should put this info to documentation.