Documentation and helper function

This project is great and I fully grasp its potential. However, the status of the documentation and the multilayer OOP where object inherits from others makes it really hard to use.

For e.g. how can one get the energy or fluence as a numpy array to calculate custom metrics? Say I have a beam and want to know the local fluence at a given depth? It's great to have visualization functions, but it's hardly useful for any quantitative interpretation. I dived a bit in the code, but most of it is non-documented and there is no documentation to explain the overall philosophy of the library.

Thanks and keep up the good work!