Sensitive volumes

The VMC interfaces do not provide functions for a user selection of sensitive volumes and the user MCApplication::Stepping() is called in all volumes. In order to speed up simulation, in Geant4 VMC (development version only) the user has a possibility to select sensitive volumes. If any selection is provided, the user MCApplication::Stepping() is called only from the selected sensitive volumes.

The selection of sensitive volumes can be done in two ways

  1. Via the following Geant4 VMC command: 
    /mcDet/addSDSelection volName1 [volName2 ...]
    The command can be applied more times, the new selection is each time added to the existing ones.

  2. Via labeling volumes directly in TGeo geometry. In this case, user has to notify Geant4 VMC about using the sensitive volumes selection from TGeo by applying Geant4 VMC command: 
    /mcDet/setSDSelectionFromTGeo true
    The volumes in TGeo geometry are set sensitive by setting the option "SV" to TGeoVolume objects: 
    TGeoVolume* myVolume = ... 
myVolume->SetOption("SV");
    User can also choose a different string than "SV" for sensitive volumes labeling. In this case, he has to notify Geant4 VMC about the label via the Geant4 VMC command: 
    /mcDet/setSVLabel MyLabel
    Note that TGeoVolume::SetOption function is implemented only in Root development version (since rev.40333) and that this option is not persistent.