how can i generate frog for a unique area?

the Atmospheric frog and the height frog are both globa as i know

You can use a post process shader on a post-process volume to add depth fog to a defined area.

Have a look at these links:

Personally I would wait for 4.16 because it looks to have new, modern volumetric fog/lighting. I’ve played with it using a github version but I believe the first preview release of 4.16 is not very far away now (Im expecting news this week but could be wrong).

Any info on what dynamic lighting/fog stuff are in the 4.16 source atm?

A few messages into page 5 onwards on the following thread is presently the best source of info that I know of:

Also someone from Epic said they were trying hard to get the first preview release of 4.16 out this week, though I cannot remember which thread that message was on.

Ah I was slightly behind the times and the 4.16 preview was announced and made available some hours ago. Plenty about the volumetric fog in the notes:

Hahaha!! This thread made me smile…