Navigation in parallel geometries

Use Cases

Current scenario

Parallel navigation is possible for the case of fast-simulation and importance-biasing. Both allow for tracking in either the tracking (mass) geometry or parallel (ghost) geometry (superimposed to the tracking one). Independent navigators are defined and associated to specialised processes regularly registered to the G4ProcessManager.
In the case of fast-simulation, more than one geometry can in principle be assigned to the same navigator.

Limitations in the old approach:

The design proposal documented here allows to overcome the limitations above and provide a generic and universal way for handling navigation in parallel geometries, where more than one navigator (and geometry) can be invoked and centrally controlled such that the final evaluation of the step to take (including eventually integration in field) is made taking into account the existance [or not] of specialised processes applied [or not] to parallel geometries.

Fast simulation envelopes

The first step which is sort of independent from the realization of a parallel navigation scheme, but is required in order to assure the consistency with some aspects of the existing design, has been to "merge" the concept of 'envelopes' used in fast-simulation and 'regions' associated to logical-volumes.
A G4Region could be easily extended to cover also the concept of an 'envelope', the result is mainly an implementation detail which requires adapting the mechanism for the scanning of the materials to consider the case of the existance of logical-volumes with NULL material pointer assigned.


Parallel Navigators

Design diagrams & descriptions:

Notes & considerations: Tests:


  1. G4PathHelper interface ready (JA)
    • by February 28th, 2008
  2. Additions to G4TransportationManager (GC)
    • by February 28th, 2008
  3. Modifications to G4ProcessManager (HK)
    • by February 28th, 2008
  4. Test for G4PathHelper completed (MV)
    • by March 15th, 2008
v.3.0, GC - Friday, 1 February 2008