I stumbled across this video while creating fog for my game. Although the material works fine but I don’t know how the Fog Height is changing.
I want a bit of an understanding of what is happening. I tried to draw it on paper, but I am unsure how the height works.
I guess we are changing the local bounds of the object and the fog is only rendered as per the bounds given to it. If it’s true, then why is it only changing in one axis?
You’re not changing the local bounds 
You’re doing something more like
( Local position - Min object position ) / object size
and then multiplying by a parameter.
The one axis is coming from subtracting the object lowest position there
So what does ( Local position - Min object position ) / object size give us that influences the height of the fog?
Plus, Local Position, Min Object Position and Object size are vector 3, right? So even after solving the equation, we should have all three vectors.
I just understand that extinction defines the intensity of the fog, so how can we control how the fog fills up using that property?
Sorry, I might sound a bit dumb.