#include "TGeoManager.h"
#include "TGeoVolume.h"
#include "TGeoMaterial.h"

void materials() {
  gROOT->ProcessLine(".x $ROOTSYS/tutorials/geom/rootgeom.C");
  TList *materials = gGeoManager->GetListOfMaterials();
  TIter next(materials);
  TGeoMaterial *mat;
  while ((mat = (TGeoMaterial*)next())) mat->SetTransparency(50);
  gGeoManager->GetTopVolume()->Draw("ogl");
}