Gernal Particle Source and Optical functions

Is there a way to set the optical functions alpha, beta, gamma of the beam in the General Particle Source? I have not found anything in the GPS_manual.

Many thanks in advance

Which optical functions are these? They’re not related to optical photons in Geant4, I don’t think.

The optical functions of a accelerator beam. I wanted to describe the initial particle distribution by the optical functions ( Twiss parameters).

I don’t think there is anything covering them in GPS. It seems to me that you should be able to implement the phase space equations in your PrimaryGeneratorAction using the Particle Gun. However, I don’t know how easy that would be.