Fog
Fog or fade is the effect in which the colors of things and level geometry is modified by distance. There is a global fade color set in MAPINFO with the fade property, but individual sectors can vary. First, sectors with a sky ceiling will use the outsidefog color defined, if any; as will sectors of type 87:Sector_Outside. Secondly, any sector can have its own colored fog set in one of the following three ways:
- In UDMF only: with the fadecolor sector property.
- With a FadeSetter thing placed in the sector.
- With the Sector_SetFade special, which can be used dynamically in a script.
You can use the testfade console command to test a color from within the game.
Fullbright sprites do not appear full bright in fogged sectors.
There is more difference between fogless sectors (fade #000000) and foggy sectors than between the two extremes of dark fog (fade #000001 vs. fade #FFFFFF).
OpenGL
Some additional options are available to the OpenGL renderer.
Since a fade is sometimes used to change the ambiance of a level rather than to simulate fog, the console variable gl_spritebrightfog can be used to force bright sprites to remain bright in fog.
In MAPINFO, the fog density can be modified, for both outside and inside fog. Fog can also be applied to the sky.