EventDisplay Events
===================

Visualization of an event
-------------------------

.. image:: ./Images/EventDisplay_Event.png
	:width: 600
	:alt: Event Display

An event can be displayed via ``Eve browser``, ``FairEventManager``, tab ``Info``.
Either one can use the ``Update`` button or switch to a specific event via
``Current Event:`` (see red arrows).
It is advisable to disable the visualization of the geometry or set the
transparency via the tab ``Graphics`` to a high value.

Depending on the root files provided, different sets of data are displayed:

* sim file provided
   * Display of MC tracks
    
     If ``FairRunSim::SetStoreTraj`` is set to ``true`` in the sim macro, the MC tracks are displayed in the event display.
     The tracks contain the type of particle its MC momentum and the flight path. The flight path is plotted using
     fulcrums stored in the sim process. Therefore the displayed track is interpolated in between the fulcrums and not precise.
     A single track can be selected in the event display and its properties are displayed.
     The complete list of tracks is listed in the ``Eve browser``, in the folder ``FairGeoTracks``. Here the display of the
     different particle types can be enabled and disabled.
     
   * Display of MC points
   
     The MC points of the different detectors are displayed as boxes.
     The color of the points can be set in the ``eventDisplay.C`` macro.
     
   * Display of EMC data
   
     To display MC data from the EMC two methods exist ``PndEmcHitDraw`` and ``PndEmcHitCaloDraw``.
     ``PndEmcHitDraw`` draws a box at the crystal position with the deposited energy as value.
     ``PndEmcHitCaloDraw`` displays the deposited energy as a tower with different hight at the crystal
     position on a barrel sitting approx. at the position of the EMC.
     
* digi file provided
   * Display of reconstructed hits
   
     The position of the reconstructed is displayed as boxes. The corner of the box corresponds to the
     reconstructed hit position. Single hits or ranges of hits can be disabled from visualization via
     the tab ``Style``. The ``Overflow`` behavior should be set to ``Cut``. The ``Main range`` can then be used
     to display only specific groups of hits. The range number usually corresponds to the hit id (the position in
     the TClonesArray) of the data.
    
   * Display of STT hits
     
     Using the standard ``FairHitDraw`` to display the STT reconstructed hits gives the mid position of the fired tube
     but no isochrone information.
     A more realistic view is the visualization via ``PndSttIsochroneDraw`` which draws a tube with the length and position
     of the fired straw tube and a radius matching the isochrone radius.
     
* reco file provided
   * Display of reconstructed tracks
   
     Which reconstructed tracks are displayed is selected in the ``eventDisplay.C`` macro by giving the branch name of the
     ``PndTrack`` data. For each track two data sets are drawn. The first one are the track parameters given by a momentum vector
     at the start of the track in red and the momentum vector at the end of the track in blue. For the barrel part also a
     helix segment can be plotted. Forward going tracks are missing this feature.
     
     The second data set is a collection of hits belonging to a track. As default, all hits of all tracks are displayed.
     If just a specific track should be plotted one can select this track via the tab ``Style``. One has to set ``Overflow`` to ``Cut``
     and then use the ``Main range:`` to select the specific track. The track number here corresponds to the track number
     for the track parameters.