void PMTs_geom()
{
   TEveUtil::AssertMacro("PMTs.C");

   // Init Eve
   TEveManager::Create();

   TEveGeoTopNode *enode = new TEveGeoTopNode(gGeoManager, gGeoManager->GetTopNode());
   enode->SetVisLevel(10);
   gEve->AddGlobalElement(enode);

   // Set default colors, based on Z of the material.
   gGeoManager->DefaultColors();

   // Reduce output from TGeoManager
   TGeoManager::SetVerboseLevel(0);

   // Switch to white backround.
   gEve->GetViewers()->SwitchColorSet();

   // Ask for redraw of changed scenes / viewers.
   // Argument true tells GL to reset the camera (set it up for size of
   // current scene contents).
   gEve->Redraw3D(kTRUE);

}