hmm, I see your point. It’s a tricky one.
My main concern is that because i’m lighting the inside of the building with the sky light only, the exposure outside the building is incredibly bright, compared to the inside, so will look terrible if people accidentally wander through a wall. So I’m splitting the exterior and interior into two seperate VR files. Perhaps you could add a portal material which can be assisnged to windows panes?
This way you could add the portal material to the windows, and then have a multipler slider to control how much it amplifies the light coming from the backface (light travels in the direction of the normal). Then you could have one light setting for entire scenes and still get similar exposure outside and inside.
Turning down the skylight and instead lighting the internals with many lights is slower to render and not as realistic i’ve found.
But yes, an outer boundary would be good too, which displays just blackness, or a starfield with a “go back to scene” warning in semi transparent flashing green text perhaps.