Re: Local coordinates in a volume+external event loop

Hi,

On 03/01/2011 11:55 AM, Ivana Hrivnacova wrote:
> Hi Filimon,
>
> See my replies below.
>
> Best regards,
>
> Ivana
>
> On 02/28/2011 10:54 AM, Filimon Roukoutakis wrote:
>> Hi, I would like to retrieve the local coordinates of a hit inside a
>> specific volume (defined through TGeo), ie the coordinates should be
>> extending from the center of the volume (0, 0, 0) up to its boundaries
>> (for example length and radius of a cylinder as maximum values). Is the
>> gGeoManager->MasterToLocal the correct and fastest way to do this? (I
>> plan to have this call in Stepping function so it should be as efficient
>> as possible).
>
> I believe, this is ok when you run G3 with TGeant3TGeo and Geant4 with
> G4Root navigation (Andrei, could you, please, confirm.)
> Only if you would want to run also with Geant4 native navigation, than
> you should use gMC->Gmtod(..) instead.
Ok, thanks, we are only playing with TGeo geometries and navigation in my use case so this should be OK. I guess then what one expects is to get the x, y, z values extending up to max dimensions defined by the bounding box of each volume (2*dx, 2*dy, 2*dz) or is it really more constrained to the actual geometry of the volume? To give you an idea of what I am doing, we have several thousand of fibers placed in a bulk absorber and we need to know the point along each fiber where we register a hit. This cannot be accomplished by gMC->TrackPosition(x, y, z) because this returns the coordinates in the top volume, right? So the idea is to get the (z)-coordinate along the length of the fiber (could be the x, y, or z according to the actual orientation) and store it during simulation so at digitization time we do not need to perform this over and over again with different digitization params. This is why I need the MasterToLocal, hopefully it works as I think. I do not know whether there is a simpler approach to this use-case...
>
>
>> Another question, there is a TVirtualMC::ProcessEvent function. Is this
>> called at some point in the simulation? The reason I am asking is that I
>> would like to have an external event loop for the simulation if possible
>> but as far as I can see for example in TGeant4::ProcessRun(int)
>> G4RunManager::BeamOn(int) is called directly (at least last time I
>> checked some time ago). Is there a way to have an externally-driven
>> event loop bypassing this then?
>
> The external event loop is not possible with VMC + Geant4;
> user can call only gMC->ProcessRun(int) as you found. There are
> available MCApplication::BeginEvent() and MCApplication::FinishEvent()
> functions, where you can put the necessary actions on the event level.
> Could you give us more details, why do you need the external event loop?
I am combining VMC+TProofLite. It works but the user does not get an output while the long simulation runs (in this very first implementation I have). I guess the obvious solution since no external event loop is possible in the general case would be to move the progress indicator of Proof inside TVirtualMCApplication::FinishEvent(). Andrei, what would be the most appropriate way for both batch and graphical mode? Is there any Getter to accomplish this, maybe? cheers, filimon
>
>
> Thanks,
>> filimon
>