Implement the option CANDLE to draw 2D histograms:

{
   TH2F *hcandle = new TH2F("hcandle","Option CANDLE example ",40,-4,4,40,-20,20);
   Float_t px, py;
   for (Int_t i = 0; i < 25000; i++) {
      gRandom->Rannor(px,py);
      hcandle->Fill(px,5*py);
   }
   gStyle->SetPalette(1);
   hcandle->SetMarkerSize(0.5);
   hcandle->Draw("CANDLE");
}