GetCurrentPoint gives zeros

ROOT
#1

hi rooters,
When I use say:
const Double_t* p = helix.GetCurrentPoint();
all p[0],p[1],p[2] values are equal to zero.
Any Advice?

#2

Can you be more precise ? what is “helix” ?

#3

Hi cout,
I am trying to describe the trajectory of charged particles passing through magnetic field. I used TGeoHelix function:

TGeoHelix helix(Double_t curvature, Double_t step, Int_t charge = 1);

I was following this example,
root.cern.ch/root/roottalk/roott … gltracks.C

and didn’t get any errors but all points have zero value.

#4

Hi,

You have to properly initialize the helix object, assuming you have called the non-default constructor:

   fieldp->InitPoint(x,y,z);
   fieldp->InitDirection(dx,dy,dz);
   fieldp->UpdateHelix();
   fieldp->Step(crtstep);

then get current point and direction.
Best,

#5

Hi Andrei,

That worked… Thanks a lot