Each colormap is a table 256 bytes long. It is indexed using a pixel value (from 0 to 255) and yields a new, brightness-adjusted pixel value. The first 32 colormaps (0-31) are used for sector brightness, with colormap 0 being the brightest and 31 is the darkest. Walls, flats, and sprites are assigned a colormap based both on the sector they are in and the distance they are from the viewer. Walls additionally have their colormap modified by what direction they are facing. Colormap 6 is used to give a sprite partial invisibility by remapping pixels behind the object to darker shades of nearby pixels. This is replaced by the TINTTAB function in Heretic and Hexen.