geom_alice_its.C

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/// \file
/// \ingroup tutorial_eve
/// Shows geometry of ALICE ITS.
///
/// \image html eve_geom_alice_its.png
/// \macro_code
///
/// \author Matevz Tadel
 
#include "TEveManager.h"
#include "TEveGeoNode.h"
 
#include "TGeoManager.h"
#include "TGeoNode.h"
#include "TGeoVolume.h"
#include "TGeoMedium.h"
 
#include "TString.h"
 
void geom_alice_its()
{
   TEveManager::Create();
 
   gGeoManager = gEve->GetGeometry("http://root.cern/files/alice.root");
 
   TGeoNode *node = gGeoManager->GetTopVolume()->FindNode("ITSV_1");
   TEveGeoTopNode *its = new TEveGeoTopNode(gGeoManager, node);
   gEve->AddGlobalElement(its);
 
   gEve->Redraw3D(kTRUE);
}
 
//==============================================================================
// Demonstrate extraction of volumes matching certain criteria.
//==============================================================================
 
//
// 1. Creation:
//    root
//      .L geom_alice_its.C+
//      extract_ssd_modules()
//      .q
//    This creates file "test-extract.root" in current dir.
//
// 2. Viewing:
//    root
//      .x show_extract.C("test-extract.root")
 
TEveGeoNode *descend_extract(TGeoNode *node)
{
   // We only return something if:
   // - this is a node of interest;
   // - one of the daughters returns something of interest.
 
   const TString material("ITS_SI$");
 
   TEveGeoNode *res = nullptr;
 
   auto medium = node->GetVolume()->GetMedium();
   if (medium && material == medium->GetName()) {
      // Node of interest - instantiate eve representation and return.
      res = new TEveGeoNode(node);
      return res;
   }
 
   Int_t nd = node->GetNdaughters();
   for (Int_t i = 0; i < nd; ++i) {
      auto ed = descend_extract(node->GetDaughter(i));
 
      if (ed) {
         if (res == nullptr)
            res = new TEveGeoNode(node);
         res->AddElement(ed);
      }
   }
 
   return res;
}
 
void extract_ssd_modules()
{
   const TString kEH("extract_ssd_modules");
 
   TEveManager::Create();
 
   gGeoManager = gEve->GetGeometry("http://root.cern/files/alice.root");
 
   Bool_t s = gGeoManager->cd("/ITSV_1/ITSD_1/IT56_1");
   if (!s) {
      Error(kEH, "Start node not found.");
      return;
   }
 
   auto node = gGeoManager->GetCurrentNode();
 
   TEveGeoNode *egn = descend_extract(node);
 
   if (egn == nullptr) {
      Warning(kEH, "No matching nodes found.");
      return;
   }
 
   egn->SaveExtract("test-extract.root", "AliSDD", kTRUE);
}