Find_displacement works via phase correlation. So, it’s comparing FFTs. It greatly improves it’s ability to operate thanks to the strong edges.
Honestly, we don’t really have a great framework for pose estimation of the camera, though. However, you can pretty much do any math you like via ULAB onboard using ndarrays. You can convert images into ndarrays, run FFTs on the values, and etc. So, any math you want to do onboard is possible.