|Click to enlarge picture|
Here is the code activating the fog in the background.
if foggy then
Fog (FOG_MODE, LINEAR);
Fog (FOG_COLOR, fog_colour(0)'Unchecked_Access);
Hint (FOG_HINT, FASTEST);
Fog (FOG_START, 1.0);
Fog (FOG_END, 0.4 * fairly_far);
As usual with GL, it looks very obvious, but (as usual too) it is one of the few combinations that are actually working.