Lets say you're in a room a good distance from the window. Suddenly you hear what sounds like thunder and rain falling. From a distance it appears that it's raining outside.

Is the rain real? Or is it simulated on a screen well enough you can't tell?

You have input output devices just like a computer. They don't see reality, they filter out huge amounts of data and your brain just interprets it. If our machines get good enough we may be able to blast signals directly to the brain that say it's raining and the brain wouldn't have any idea if it was simulated or not. Much in the same way it feels like we exist and not a 3d hologram an infinite distance away (or whatever other weirdness physics may or could do).