Inside the gizmo
Outside the gizmo
Near the gizmo - Render time on my machine 1:14 minutes
I always forget how to get the Vray Environment Fog to render somewhat quickly so I thought I would post my settings here so I can find them. I think the main things is that the steps should be about 1/3 the distance.
My gizmo is 6000 x 6000 x 3500 units. My units are in Feet
I used a noise for the density.
From the side