Get particle position at the end of a step

[Saluta]

I have 2 methods to get the particle position at the end of a simulation step:

1.
G4ThreeVector position  = track->GetPosition() - step->GetDeltaPosition();

2.
G4ThreeVector position  = step->GetPostStepPoint()->GetPosition();

In my code, I invoke these 2 methods in SteppingAction::UserSteppingAction() method, but these 2 methods returns different results.

Are these 2 methods different?

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_Geant4 Version:_4.11.0.p01
_Operating System:_windows subsystem linux (wsl2)
Compiler/Version:
CMake Version:

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[mcortesg]

Dear Saluta,

Yes, they calculate different things. When UserSteppingAction() is called, track->GetPosition() gives already the post-step point position. If you want them to give the same result, you do not need to substract the step delta position.

Miguel

[Saluta]

Thank you so much for your answer.

So in UserSteppingAction() any information from track, say,
track->GetMomentum(),
track->GetTotalEnergy(),
track->GetPosition(),
will return identical result as from
step->GetPostStepPoint->GetXXX(),
right?

[mkelsey]

Yes, that should be correct. My understanding is that step->GetDeltaPosition() is a “convenience function”, so you don’t have to manually do GetPostStepPoint()->GetPosition() - GetPreStepPoint()->GetPosition().