ParticleFilters.h

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#ifndef LARCOREALG_COREUTILS_PARTICLEFILTERS_H
#define LARCOREALG_COREUTILS_PARTICLEFILTERS_H

// LArSoft libraries

// ROOT libraries
#include "TGeoMatrix.h" // TGeoCombiTrans
#include "TGeoVolume.h"
#include "TLorentzVector.h"
#include "TVector3.h"

// C/C++ standard libraries
#include <array>
#include <utility> // std::move()
#include <vector>

namespace util {

  struct KeepByPositionFilterTag {};

  class PositionInVolumeFilter : public KeepByPositionFilterTag {
  public:
    using Point_t = std::array<double, 3>;

    struct VolumeInfo_t {
      VolumeInfo_t(TGeoVolume const* new_vol, TGeoCombiTrans const* new_trans)
        : vol(new_vol), trans(new_trans)
      {}

      TGeoVolume const* vol;       
      TGeoCombiTrans const* trans; 
    };                             // VolumeInfo_t

    using AllVolumeInfo_t = std::vector<VolumeInfo_t>;

    PositionInVolumeFilter(std::vector<VolumeInfo_t> const& volumes) : volumeInfo(volumes) {}
    PositionInVolumeFilter(std::vector<VolumeInfo_t>&& volumes) : volumeInfo(std::move(volumes)) {}

    bool mustKeep(Point_t const& pos) const
    {
      // if no volume is specified, it means we don't filter
      if (volumeInfo.empty()) return true;
      double local[3];
      for (auto const& info : volumeInfo) {
        // transform the point to relative to the volume
        info.trans->MasterToLocal(pos.data(), local);
        // containment check
        if (info.vol->Contains(local)) return true;
      } // for volumes
      return false;
    } // mustKeep()

    bool mustKeep(TVector3 const& pos) const
    {
      return mustKeep(Point_t{{pos.X(), pos.Y(), pos.Z()}});
    }

    bool mustKeep(TLorentzVector const& pos) const
    {
      return mustKeep(Point_t{{pos.X(), pos.Y(), pos.Z()}});
    }

  protected:
    std::vector<VolumeInfo_t> volumeInfo; 

  }; // PositionInVolumeFilter

} // namespace util

#endif // LARCOREALG_COREUTILS_PARTICLEFILTERS_H