void reset_vis()
{
   TGeoManager::Import("rootgeom.root");

   TGeoIterator iter(gGeoManager->GetMasterVolume());

   TGeoNode *node;

   while ((node = iter.Next())) {
      // printf("Name %s\n", node->GetName());
      node->GetVolume()->ResetAttBit(TGeoAtt::kVisOnScreen);
   }

   gGeoManager->Export("rootgeom2.root");
}