This tutorial explains how to download private or ratelimited (Sign in to confirm you're not a bot) videos & playlists, or rather: videos you need to be logged in for. I can't guarantee this will work ...
VISFD is a small C++ template library for 3D image processing ("visfd.hpp") which is useful for extracting geometric shapes, volumes, and other features from 3-D volumetric images (eg. tomograms).