TClonesArray fTestLines ("TPolyLine3D",1000);

void geom_example_lines(){

  gSystem->Load("libGeom");
  
  TGeoManager *geom_example = new TGeoManager("geom_example","geom_example.C");
 
  TGeoMaterial *mymat = new TGeoMaterial("BERILLIUM",9.01,4,1.848);
  mymat->SetUniqueID(   5);

  TGeoMedium *mymed = new TGeoMedium("BERILLIUM",3,5,0,1,10,2,0.1000000E+11,0.2163378,0.2000000E-03,0.2261152E-01);
  TGeoVolume *TOP_VOL = gGeoManager->MakeTube("TOP_VOL",mymed,0,210,350);
  TOP_VOL->SetVisibility(0);

  // ---  
  TGeoVolume *IDET = gGeoManager->MakeTube("ITOF",mymed,5.8,6.03,10);
  IDET->SetVisibility(0);
  IDET->SetLineColor(5);

  gGeoManager->SetTopVolume(TOP_VOL);

  TOP_VOL->AddNode(IDET,1,gGeoIdentity);
  TGeoVolume *ITUB = IDET->Divide("ISLB",2,12,0,30);
  // ---  
  gGeoManager->CloseGeometry();

  cout << " ---> " << gGeoManager->GetTopVolume()->GetName() << endl;
  cout << " ---> " << gGeoManager->GetTopVolume()->GetNode(0)->GetName() << endl;

  gGeoManager->GetTopVolume()->VisibleDaughters(1);

  TCanvas *fMainCanvas = new TCanvas("GeomCanvas","Geometry",100,100,400,400);

  gGeoManager->GetTopVolume()->Draw("");
  for(Int_t nl=0;nl<30;nl++){
    new (fTestLines[nl]) TPolyLine3D(2);
    Double_t radius = 6;
    if(nl>27) radius = 10;
      Double_t x,y,z;
      gRandom->Circle(x,y,radius);
      z = gRandom->Gaus(0,10);
      //    hits.SetPoint(i,x,y,z);
      TPolyLine3D *curline = (TPolyLine3D *)fTestLines[nl];
      curline->SetPoint(0,x,y,-z);      
      curline->SetPoint(1,x,y,z);      
      curline->SetLineColor(nl);      
      curline->SetLineStyle(nl);      
      curline->SetLineWidth(nl/2);      
  }
  for(Int_t i=0;i<fTestLines->GetEntries();i++){
    //    TPolyLine3D *myl = ((TPolyLine3D *)(fTestLines[i]));
    ((TPolyLine3D *)(fTestLines[i]))->Draw("same");
  }
  
  TGLSAViewer *fGLSAViewer = (TGLSAViewer *) fMainCanvas->GetViewer3D("ogl");
  //TGLSAViewer *fGLSAViewer = (TGLSAViewer *) fMainCanvas->GetViewer3D();


  // If you need to clear all lines or all markers:
  // fTestLines.Delete();
  // hits.Delete();
}