[Chimera-users] mask

I have a volume whose density values are -127 thru 127. Zero is a valid density & approximately the peak of the Guassian distribution. I would like to use the command mask. It sets the unmasked density values to zero. How can I set the unmasked density values to -128 using the mask command? Will I need to hack the code? Matthew Dougherty National Center for Macromolecular Imaging Baylor College of Medicine ================================================= =================================================