Scaled visualisation of Beams

[DavidDierickx]

As it is, beams only visualise in the Napari window with the same visual length regardless of the propagation distance. This can be changed manually through the console but preferably an option to scale it (either automatically with a fixed "pixel size" along the propagation distance) or with a slider to determine the relative Z scaling would be great.

[DavidDierickx]

As an added note, the beam visualisation DOES scale if you change the number of steps (i.e. 20 steps will give you twice the visualisation distance), however increased steps should only increase the effective resolution of the z axis, while maintaining the visualisation distance.

[DavidDierickx]

Pixel size of the simulation also scales the X/Y components of the visualisation. I don't think this is intuitive.