Hi!
How can we make fog with only hdri lightning?
I have a volume material in render settings/scene environment/global volume.
And that works fine if I´m using arealights but if I´m only using hdri lightning or corona sky the scene has no ligth at all..??
There was no problem, I had the absortion distance to short.. First time making fog 
You may also sometimes need to experiment with the “enviro distance” value in Devel/debug settings (to enable them go to Corona > Preferences and check “Enable devel/debug mode”).
It basically tells Corona how far away from the camera the environment is. As if it was a glowing sphere around your camera.
Ok, good to know. Thanks