{
  TH3D* small3 = new TH3D("small3","3D small;x;y;z",
                 8,0.,8., 8,0.,8., 8,0.,8.);
  TH3D* medium3 = new TH3D("medium3","3D medium;x;y;z",
                 8,0.,8., 8,0.,8., 8,0.,8.);
  TH3D* large3 = new TH3D("large3","3D large;x;y;z",
                 8,0.,8., 8,0.,8., 8,0.,8.);
//
  Double_t weight;
  Int_t ibin;
  for (Int_t ixbin=0; ixbin<=9 ; ixbin++) {
    for (Int_t iybin=0; iybin<=9 ; iybin++) {
      for (Int_t izbin=1; izbin<=8; izbin++) {
//
         weight = 1.;
//         weight = ixbin+iybin+izbin;
//
         ibin = small3->GetBin(ixbin,iybin,izbin);
         small3->AddBinContent(ibin,weight);
         medium3->AddBinContent(ibin,weight);
         large3->AddBinContent(ibin,weight);
      }
//  Add to medium3 for the z overflow and underflow bins
//  Add twice to the large3 z- overflow and underflow bins
         weight = 1.;
//         weight = ixbin+iybin;
      ibin = medium3->GetBin(ixbin,iybin,0);
      medium3->AddBinContent(ibin,weight);
      large3->AddBinContent(ibin,weight);
      large3->AddBinContent(ibin,weight);

         weight = 1.;
//         weight = ixbin+iybin+9;
      ibin = medium3->GetBin(ixbin,iybin,9);
      medium3->AddBinContent(ibin,weight);
      large3->AddBinContent(ibin,weight);
      large3->AddBinContent(ibin,weight);
    }
  }
// Make xy projections of each 3D histogram
  TH2D* sma2 = (TH2D*)small3->Project3D("xy")->Clone("sma2");
  TH2D* med2 = (TH2D*)medium3->Project3D("xy")->Clone("med2");
  TH2D* lar2 = (TH2D*)large3->Project3D("xy")->Clone("lar2");
//
  printf("Entries for small3 = %d \n",
         small3->Integral(0,9,0,9,0,9));
  printf("Entries for sma2   = %d \n",
         sma2->Integral(0,9,0,9));
  printf("Entries for medium3 = %d \n",
         medium3->Integral(0,9,0,9,0,9));
  printf("Entries for med2    = %d \n",
         med2->Integral(0,9,0,9));
  printf("Entries for large3 = %d \n",
         large3->Integral(0,9,0,9,0,9));
  printf("Entries for lar2   = %d \n",
         lar2->Integral(0,9,0,9));
}