How to invert a post processing volume?

Hello, I am asking a rather unusual, yet difficult question. My goal is to have the whole entire screen to be blurred, except for one small area.

For example, suppose there is a post processing volume enclosing a chair. I want everything outside that chair to be blurred.

Any help will be appreciated.

Volumes are used to turn post processing on/off, not affect just an area of the screen. If what you are asking to do is have an area around the chair in focus and everything out of focus, you can use depth of field to achieve that. However that is focal point and range controlled so if the player moves, the DoF moves with their camera

Ok, I’ll try to be more specific. The effect that I am trying to achieve is to have an object that the player is looking at to be in focus. With all other areas of the screen blurred. Like having a focal point instead of a distance, with the transition region being more like a radius.

Yep, that’s what the DoF does. The technical-ish terms are focal point and zone of confusion. Use the depth of field post process

Ok thanks, I’m still getting used to the engine.