TH2 coz & empty bins

Hello rooters,
We are having a problem dealing with a THProfile2D drawn with the "col" option. I fear this might have been already discussed in the past, forgive me if I'm reopening the discussion. The TProfile2D we use is filled incrementally and allows both positive and negative values. When displayed it is plotted in color ("COL"). Now, the trouble is the THistPainter paints the empty bins if zmin < 0, doesn't paint them if otherwise.

For us is important to distinguish between empty bins and bins which value is 0 or close to 0. Isn't there a way to force the empty bins to be hidden? I have found it for the lego plot ("0" option) but not for the other drawing modes.

Thank you in advance for any help.
Alessandro

  ETH Zurich
  Dr. Alessandro Thea
  Institute for Particle Physics

  CERN, European Laboratory for Particle Physics,   CH-1211, Geneve 23, Switzerland,
  PH/UCM, Office 32-2-B03, Mailbox: F17500

  Tel: +41-76-487-1800 E-Mail: Alessandro.Thea_at_cern.ch