Anti-Global Illumination Volume

So I’m working on an open-world game, and the outside world looks absolutely fantastic. However, if I wish to achieve realistic lighting for space underground, I’m left with the choice of separating the said space from the outside world much like The Elder Scrolls series does. I would like to achieve realistic lighting underground, so that when you enter a cave, you can (with a volume) disable the global illumination’s indirect lighting that occurs. Even if there was a variable for transitional lighting, so that the immediate entrance will still have some global illumination and disappear over time (Maybe that can even be achieved by dropping a lightmass importance volume at the entrance to calculate indirect lighting and bounce lighting?). Anyways, just a thought I thought I would throw out there. If the transitional lighting variable is set to 0, that could always simply have NO transitional lighting, for basements, or levels that lighting would just stop after a certain degree (Such as a well that goes down 30 feet before it opens up to a cavern - - none of it would require indirect lighting beyond a certain point, so everything in the Anti-GI Volume would be pitch black with the exception of direct lighting (Such as the sun at high noon shining further down the well than at any other time).

Sound like you are describing eye adaptation… That already exists…

So you just exclude that part from your lightmapp importance space.

But then the illuminated spot would cast, realistically, diffuse this light into the cavern, so making it not pitch black.

I am trying to describe a transitional fading of indirect light from the outside world (particularly from the skylight) at the cave entrance from full indirect lighting, to none. In my particular project, all underground is affected by skylight indirect lighting, therefore not dark at all.

See above.

Not necessarily, as having a single isolated source of light shine down a long well would create a spotlight effect rather than illuminate the cavern by too much.

I don’t know why I forgot to mention skylight’s indirect lighting in my original post, I apologize for the confusion.

It should not be affected by default. If skylight bounces can’t access some areas(caves for example) due to shadowing then these areas should look black.

What lighting system do you use?
Static with Lightmass or dynamic with Distance fields, movable lights and etc.

For static lighting you can use post process volumes for caves and adjust GI intensity through there. For dynamic lighting you can set the skylight’s color to a dark value via trigger volumes for caves, which is basically what you are requesting and it requires you to create only one volume as a BP and then set the skylight > light color and use it anywhere in the level and as many as you like. Reflection capture actors also help a little.

It is the light bouncing of the spotlight that should cause some illumination. If you imagine the light shooting straight up again, after creating the spotlight, the you wouldnt see it at all. It would be like a (clean) mirror…
If you can see the spotlight on the floor from within the cave, light must be bouncing arund from it in the cave (and into your eye).