parallel_world.C File Reference

Detailed Description

Misaligning geometry generate in many cases overlaps, due to the idealization of the design and the fact that in real life movements of the geometry volumes have constraints and are correlated.

This typically generates inconsistent response of the navigation methods, leading to inefficiencies during tracking, errors in the material budget calculations, and so on. Among those, there are dangerous cases when the hidden volumes are sensitive. This macro demonstrates how to use the "parallel world" feature to assign highest navigation priority to some physical paths in geometry.

void align();

//______________________________________________________________________________
void parallel_world(Bool_t usepw=kTRUE, Bool_t useovlp=kTRUE)
{
   TGeoManager *geom = new TGeoManager("parallel_world", "Showcase for prioritized physical paths");
   TGeoMaterial *matV = new TGeoMaterial("Vac", 0,0,0);
   TGeoMedium *medV = new TGeoMedium("MEDVAC",1,matV);
   TGeoMaterial *matAl = new TGeoMaterial("Al", 26.98,13,2.7);
   TGeoMedium *medAl = new TGeoMedium("MEDAL",2,matAl);
   TGeoMaterial *matSi = new TGeoMaterial("Si", 28.085,14,2.329);
   TGeoMedium *medSi = new TGeoMedium("MEDSI",3,matSi);
   TGeoVolume *top = gGeoManager->MakeBox("TOP",medV,100,400,1000);
   gGeoManager->SetTopVolume(top);

   // Shape for the support block
   TGeoBBox *sblock = new TGeoBBox("sblock", 20,10,2);
   // The volume for the support
   TGeoVolume *support = new TGeoVolume("block",sblock, medAl);
   support->SetLineColor(kGreen);

   // Shape for the sensor to be prioritized in case of overlap
   TGeoBBox *ssensor = new TGeoBBox("sensor", 19,9,0.2);
   // The volume for the sensor
   TGeoVolume *sensor = new TGeoVolume("sensor",ssensor, medSi);
   sensor->SetLineColor(kRed);

   // Chip assembly of support+sensor
   TGeoVolumeAssembly *chip = new TGeoVolumeAssembly("chip");
   chip->AddNode(support, 1);
   chip->AddNode(sensor,1, new TGeoTranslation(0,0,-2.1));

   // A ladder that normally sags
   TGeoBBox *sladder = new TGeoBBox("sladder", 20,300,5);
   // The volume for the ladder
   TGeoVolume *ladder = new TGeoVolume("ladder",sladder, medAl);
   ladder->SetLineColor(kBlue);

   // Add nodes
   top->AddNode(ladder,1);
   for (Int_t i=0; i<10; i++)
      top->AddNode(chip, i+1, new TGeoTranslation(0, -225.+50.*i, 10));

   gGeoManager->CloseGeometry();
   TGeoParallelWorld *pw = 0;
   if (usepw) pw = gGeoManager->CreateParallelWorld("priority_sensors");
// Align chips
   align();
   if (usepw) {
      if (useovlp) pw->AddOverlap(ladder);
      pw->CloseGeometry();
      gGeoManager->SetUseParallelWorldNav(kTRUE);
   }
   TString cname;
   cname = usepw ? "cpw" : "cnopw";
   TCanvas *c = (TCanvas*)gROOT->GetListOfCanvases()->FindObject(cname);
   if (c) c->cd();
   else   c = new TCanvas(cname, "",800,600);
   top->Draw();
//   top->RandomRays(0,0,0,0,sensor->GetName());
   // Track random "particles" coming from the block side and draw only the tracklets
   // actually crossing one of the sensors. Note that some of the tracks coming
   // from the outer side may see the full sensor, while the others only part of it.
   TStopwatch timer;
   timer.Start();
   top->RandomRays(100000,0,0,-30,sensor->GetName());
   timer.Stop();
   timer.Print();
   TView3D *view = (TView3D*)gPad->GetView();
   view->SetParallel();
   view->Side();
   if (usepw) pw->PrintDetectedOverlaps();
}

//______________________________________________________________________________
void align()
{
// Aligning 2 sensors so they will overlap with the support. One sensor is positioned
// normally while the other using the shared matrix
   TGeoPhysicalNode *node;
   TGeoParallelWorld *pw = gGeoManager->GetParallelWorld();
   Double_t sag;
   for (Int_t i=0; i<10; i++) {
      node = gGeoManager->MakePhysicalNode(TString::Format("/TOP_1/chip_%d",i+1));
      sag = 8.-0.494*(i-4.5)*(i-4.5);
      TGeoTranslation *tr = new TGeoTranslation(0., -225.+50.*i, 10-sag);
      node->Align(tr);
      if (pw) pw->AddNode(TString::Format("/TOP_1/chip_%d",i+1));
   }
}

Author

Andrei Gheata

Definition in file parallel_world.C.