Hi guys, Thanks for the wonderful work on Kwant! I want to use it to simulate disordered systems in optics, I was able to make it works quite simply, see my commented notebook here : https://github.com/wavefrontshaping/WFS.net/blob/master/Kwant_disordered_wav... But I have two issues: 1/ In order to retrieve the internal field for a given input, the only way I found was to get the internal fields for **all** the modes from a lead using `kwant.wave_function()` and then project my input wavefront. It is clearly not efficient as I force the solver to compute the internal field for all the modes instead of directly solving it for one specific input. 2/ One of my goals would be to go to 3d waveguides. There is a picture of a 3d system on the Kwant website (https://kwant-project.org/about#numerical-experiment-flying-qubit) but I did not find anything in the documentation nor in the paper related to the figure to help me to implement a 3d system. Is there a *reasonably* easy way to do it? Thanks! Sebastien