Understand how input and output work in Geant4

[andrewgait]

Following running an example in Geant 4 #7, understand how input and output work.

[andrewgait]

Some work was done towards this goal in the first sprint of the project, but more work is required to understand how the links between Geant4 and Mitsuba3 work.

[andrewgait]

Input in Geant4 is done programmatically by specifying various (predefined) objects in code in a DetectorConstruction class as defined in eg. basic example 1 at https://geant4-userdoc.web.cern.ch/Doxygen/examples_doc/html/ExampleB1.html.

Output from Geant4 in these basic examples is what you see in the visualiser once the run has been successful. For the purposes of previous work in the Manchester group, the Rich1.gdml file is effectively an output file of what can be seen in the visualiser when setting up a RICH1 detector. More work may be required in the future to understand the code that created this GDML file.