Field Name             Bits   Default Description
ENABLE                 0      0x0     Enable for fog blending
                                      POSSIBLE VALUES:
                                      00 - Disables fog (output matches input color).
                                      01 - Enables fog.
FN                     2:1    0x0     Fog generation function
                                      POSSIBLE VALUES:
                                      00 - Fog function is linear
                                      01 - Fog function is exponential
                                      02 - Fog function is exponential squared
                                      03 - Fog is derived from constant fog factor
