Abstract base-class for interfacing to magnetic field needed by the REveTrackPropagator.
To implement your own version, redefine the following virtual functions: virtual Double_t GetMaxFieldMag() const; virtual TEveVectorD GetField(Double_t x, Double_t y, Double_t z) const;
See sub-classes REveMagFieldConst and REveMagFieldDuo for two simple implementations.