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This example shows how to use a B field map provided by conditions data via the gear interface.

Needed to run it are:
    - a gear file (a simple, useless one is provided)
    - access to the conditions, currently provided as simple file
    - a data file containing at least one event (NOT! provided)
     
Please note: the example doesn't do anything, it only shows what must be in the processing scheme.

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The main processor is the LoadFieldFromConditionsDataProcessor.
It uses data provided by the ConditionsProcessor and references it by name, given by the parameter ""BFieldMapCollectionName""

The processor accesses the field data therein and loads it for the gear interface.

In your own processor, the magnetic field can then be accessed like:
 Provide a position vector, e.g.:
  gear::Vector3D here(1563.,12.,0.);
 Obtain the B field value at this position:
  gear::Vector3D magF = Global::GEAR->getBField().at(here);

+++++++++++++++++++++++
 optional parameters to the LoadFieldFromConditionsDataProcessor concern the definition of the coordinate system of the coil
 the only currently available field map uses the center of the coil as origin;
 this doesn't coincide with the coordinate origin of the Large Prototype,
 the default values shift the origin to match the coordinates to the LP system.

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Technical note: [the methods and the data objects is NOT an example how to do this. Standard procedure in Marlin/LCCD looks very different.
In other words: don't fiddle around with it; this needs more work on fixing the design.]