csgdemo.C: Combinatorial Solid Geometry example

// Combinatorial Solid Geometry example
// Author: Andrei Gheata
//
// Stripped down to demonstrate EVE shape-extracts.
// 1. Run root csgdemo.C
//    This will produce csg.root containing the extract.
// 2. Display the assebly as:
//    root show_extract.C("csg.root")

//____________________________________________________________________________
void csgdemo ()
{
   gSystem->Load("libGeom");

   TCanvas *c = new TCanvas("composite shape", "A * B - C");
   c->Iconify();

   if (gGeoManager) delete gGeoManager;

   new TGeoManager("xtru", "poza12");
   TGeoMaterial *mat = new TGeoMaterial("Al", 26.98,13,2.7);
   TGeoMedium   *med = new TGeoMedium("MED",1,mat);
   TGeoVolume   *top = gGeoManager->MakeBox("TOP",med,100,100,100);
   gGeoManager->SetTopVolume(top);

   // define shape components with names
   TGeoBBox   *box  = new TGeoBBox("box", 20., 20., 20.);
   TGeoBBox   *box1 = new TGeoBBox("box1", 5., 5., 5.);
   TGeoSphere *sph  = new TGeoSphere("sph", 5., 25.);
   TGeoSphere *sph1 = new TGeoSphere("sph1", 1., 15.);
   // create the composite shape based on a Boolean expression
   TGeoTranslation *tr  = new TGeoTranslation(0., 30., 0.);
   TGeoTranslation *tr1 = new TGeoTranslation(0., 40., 0.);
   TGeoTranslation *tr2 = new TGeoTranslation(0., 30., 0.);
   TGeoTranslation *tr3 = new TGeoTranslation(0., 30., 0.);
   tr->SetName("tr");
   tr1->SetName("tr1");
   tr2->SetName("tr2");
   tr3->SetName("tr3");
   // register all used transformations
   tr->RegisterYourself();
   tr1->RegisterYourself();
   tr2->RegisterYourself();
   tr3->RegisterYourself();

   TGeoCompositeShape *cs = new TGeoCompositeShape
      ("mir", "(sph * box) + (sph1:tr - box1:tr1)");

   TGeoVolume *vol = new TGeoVolume("COMP4", cs);
   vol->SetLineColor(kMagenta);
   top->AddNode(vol,1);
   gGeoManager->CloseGeometry();
   top->Draw();

   gGeoManager->SetNsegments(40);
   TEveGeoNode::SetCSGExportNSeg(40);

   TGLFaceSet::SetEnforceTriangles(kTRUE);
   TEveManager::Create();

   TGeoNode* node = gGeoManager->GetTopNode();
   TEveGeoTopNode* en = new TEveGeoTopNode(gGeoManager, node);
   en->SetVisLevel(4);
   en->GetNode()->GetVolume()->SetVisibility(kFALSE);

   gEve->AddGlobalElement(en);

   gEve->Redraw3D(kTRUE);

   en->ExpandIntoListTreesRecursively();
   en->SaveExtract("csg.root", "CSG Demo", kFALSE);
}