I would just plop down a flat landscape and a post process volume, whatever you want to be visible in the roomscape change the custom stencil buffer to 1 or some other number. Add yourself a post process material. In the post process material use a custom stencil buffer to lerp everything between white and post process input zero (regular) and tada you’ve got yourself an endless white space with your objects or characters or whatever you use the stencil on as visible. There are some nice short youtube tutorials on setting up the custom stencil buffer. Start there.