Only one type of fog settings in SH4?

Hi.

I am working on a new env. for SH4 which i will share when it's done.
Right now i am a little bit confused about fog distances in SH4.
It appears that there is only one set of parameters that control 3 types of fogs in scene.dat?
So if i change FogDistances settings number 2 or 3 there is no effect.
Only for FogDistances settings number 1 i get changes but it's for all 3 types of fogs?

 

I did test it only in single missions, im using TM0 2.5.
Also i have tried with other scene.dat files from some mods only to get the same results.
Anyone got any idea?

Cheers.