From
http://www.maximumpc.com/terminator/terminator_t.h
tml
table-based
fogging: Used by 3D accelerators, it's a type of fog-rendering technique. Fog is a general term representing all atmospheric effects: haze, mist, smoke, smog. When fogging is enabled, distant objects fade into the fog color. Both the fog color and the fog density (the rate at which objects fade as a function of their distance from the viewer) are programmable. Usually set by the programmer, table-based fog is where the fog table is indexed with a floating-point representation of one of the pixel's component. This fog table should consist of 64 density values, which are unsigned 8-bit quantity. A value of 0 indicates minimum density, and 255 indicates maximum density. Fog is applied after color combining and before alpha blending.