Problem 2462

Summary: Parallel world navigation misbehaves if parallel world volume is identical to a physical world volume
Product: Geant4 Reporter: Sergio Losilla <sergio.losilla>
Component: processes/transportationAssignee: John Apostolakis <John.Apostolakis>
Status: RESOLVED INVALID    
Severity: minor CC: asai, Makoto.Asai
Priority: P4    
Version: 11.0   
Hardware: All   
OS: All   

Description Sergio Losilla 2022-01-07 12:08:56 CET 
A minimal failing example (based on example B1) can be found here:

https://github.com/Geant4/geant4/compare/master...loximann:parallel_world_bug?expand=1

Setup:
* Removed Shape1 from physical world.
* Added a parallel world with a volume identical to Shape2

The issue:
No parallel world processes are observed:

G4WT13 > *********************************************************************************************************
G4WT13 > * G4Track Information:   Particle = geantino,   Track ID = 1,   Parent ID = 0
G4WT13 > *********************************************************************************************************
G4WT13 > 
G4WT13 > Step#       X          Y          Z         KineE         dEStep    StepLeng   TrakLeng    Volume     Process
G4WT13 >     0       0 fm       0 fm     -15 cm       6 MeV          0 eV       0 fm       0 fm   Envelope   initStep
G4WT13 >     1       0 fm       0 fm       4 cm       6 MeV          0 eV      19 cm      19 cm   Envelope   CoupledTransportation
G4WT13 >     2       0 fm       0 fm      10 cm       6 MeV          0 eV       6 cm      25 cm     Shape2   CoupledTransportation
G4WT13 >     3       0 fm       0 fm      15 cm       6 MeV          0 eV       5 cm      30 cm   Envelope   CoupledTransportation
G4WT13 >     4       0 fm       0 fm      18 cm       6 MeV          0 eV       3 cm      33 cm      World   OutOfWorld

However, if a 1 nm displacement is added to the parallel world volume, "MyParallelWorld" processes are observed.

G4WT2 > *********************************************************************************************************
G4WT2 > * G4Track Information:   Particle = geantino,   Track ID = 1,   Parent ID = 0
G4WT2 > *********************************************************************************************************
G4WT2 > 
G4WT2 > Step#       X          Y          Z         KineE         dEStep    StepLeng   TrakLeng    Volume     Process
G4WT2 >     0       0 fm       0 fm     -15 cm       6 MeV          0 eV       0 fm       0 fm   Envelope   initStep
G4WT2 >     1       0 fm       0 fm       4 cm       6 MeV          0 eV      19 cm      19 cm   Envelope   CoupledTransportation
G4WT2 >     2       0 fm       0 fm       4 cm       6 MeV          0 eV      10 Ang     19 cm     Shape2   MyParallelWorld
G4WT2 >     3       0 fm       0 fm      10 cm       6 MeV          0 eV       6 cm      25 cm     Shape2   CoupledTransportation
G4WT2 >     4       0 fm       0 fm      10 cm       6 MeV          0 eV      10 Ang     25 cm   Envelope   MyParallelWorld
G4WT2 >     5       0 fm       0 fm      15 cm       6 MeV          0 eV       5 cm      30 cm   Envelope   CoupledTransportation
G4WT2 >     6       0 fm       0 fm      18 cm       6 MeV          0 eV       3 cm      33 cm      World   OutOfWorld
Comment 1 asai 2022-01-10 19:45:49 CET 
If volumes in the "real" world and a parallel world share the volume boundary, the G4CoupledTransportation process is shown as the process that limits the step. This does NOT mean the volume in a parallel world is ignored. The following step is seen by both volumes in real world and the parallel world.

Thus what you see is a correct behavior and nothing is misbehaving. If you would like to confirm, assign a sensitive detector to the volume in the parallel world and add G4cout to see.
Comment 2 Sergio Losilla 2022-01-11 08:03:51 CET 
I added sensitive detectors and indeed you are right, I am sorry for wasting your time :-/

Has anything been fixed in recent versions? I recall that months ago I was getting wrong results with a more complicated setup involving replicas both in the physical world and the parallel world.
Comment 3 Gabriele Cosmo 2022-01-11 15:27:05 CET 
Hi Sergio, if you experience any problem you should report them giving clear evidence and way to reproduce them (and possibly as a ticket in this system rather than through posts in the Forum). Generic statements don't help either.
We are not aware of misbehaviours in this area; no issues have been reported to us.
Comment 4 Sergio Losilla 2022-01-12 07:30:25 CET 
Apparently there was an issue like the one I meant to report, but it has already been fixed:
https://geant4-forum.web.cern.ch/t/stepstatus-depending-on-scoring-mesh/6121/2