alice_esd.C

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/// \file
/// \ingroup tutorial_eve
/// Complex example showing ALICE ESD track visualization.
///
///  alice_esd.C - a simple event-display for ALICE ESD tracks and clusters
///
///
///  Only standard ROOT is used to process the ALICE ESD files.
///
///  No ALICE code is needed, only four simple coordinate-transformation
///  functions declared in this macro.
///
///  A simple geometry of 10KB, extracted from the full TGeo-geometry, is
///  used to outline the central detectors of ALICE.
///
///  All files are access from the web by using the "CACHEREAD" option.
///
///
///  ### Automatic building of ALICE ESD class declarations and dictionaries.
///
///  ALICE ESD is a TTree containing tracks and other event-related
///  information with one entry per event. All these classes are part of
///  the AliROOT offline framework and are not available to standard
///  ROOT.
///
///  To be able to access the event data in a natural way, by using
///  data-members of classes and object containers, the header files and
///  class dictionaries are automatically generated from the
///  TStreamerInfo classes stored in the ESD file by using the
///  TFile::MakeProject() function. The header files and a shared library
///  is created in the aliesd/ directory and can be loaded dynamically
///  into the ROOT session.
///
///  See the run_alice_esd.C macro.
///
///
///  ### Creation of simple GUI for event navigation.
///
///  Most common use of the event-display is to browse through a
///  collection of events. Thus a simple GUI allowing this is created in
///  the function make_gui().
///
///  Eve uses the configurable ROOT-browser as its main window and so we
///  create an extra tab in the left working area of the browser and
///  provide backward/forward buttons.
///
///
///  ### Event-navigation functions.
///
///  As this is a simple macro, we store the information about the
///  current event in the global variable 'Int_t esd_event_id'. The
///  functions for event-navigation simply modify this variable and call
///  the load_event() function which does the following:
///  1. drop the old visualization objects;
///  2. retrieve given event from the ESD tree;
///  3. call alice_esd_read() function to create visualization objects
///     for the new event.
///
///
///  ### Reading of ALICE data and creation of visualization objects.
///
///  This is performed in alice_esd_read() function, with the following
///  steps:
///  1. create the track container object - TEveTrackList;
///  2. iterate over the ESD tracks, create TEveTrack objects and append
///     them to the container;
///  3. instruct the container to extrapolate the tracks and set their
///     visual attributes.
///
/// \image html eve_alice_esd.png
/// \macro_code
///
/// \author Matevz Tadel
 
void alice_esd()
{
   const char* esd_file_name = "http://root.cern/files/alice_ESDs.root";
   TFile::SetCacheFileDir(".");
   TString lib(Form("aliesd/aliesd.%s", gSystem->GetSoExt()));
 
   if (gSystem->AccessPathName(lib, kReadPermission)) {
      TFile* f = TFile::Open(esd_file_name, "CACHEREAD");
      if (!f) return;
      TTree *tree = (TTree*) f->Get("esdTree");
      tree->SetBranchStatus ("ESDfriend*", 1);
      f->MakeProject("aliesd", "*", "++");
      f->Close();
      delete f;
   }
   gSystem->Load(lib.Data());
   gROOT->ProcessLine(".x run_alice_esd.C");
}