For some time I have been looking for a way to achieve something similar than the “Fake crystal” thing that can be found in Prey.
You can notice this effect in the following video around the minute 15:45 (SPOILER ALERT)
I have tested a few things but can not achieve the same effect.
I have a render texture acting as a window and a camera in other room, but I find so difficult to get the sensation of depth when moving and looking around.
I am probably failing with the maths when moving the camera with the character in an attempt of making this work.
Please forgive my english, English is not my first language.