Yeah I know about those threads.
I never understood how the distance from your monitor is relevant. It's not as if getting closer or farther changes the size of objects rendered on the screen. Ideally everyone should be close enough to see things clearly on their monitors.
Moving your head closer or further away doesn't make objects on the screen bigger on smaller, but it does make the size of the objects as perceived in your eyes bigger and smaller. To make objects appear in the same size in game as in reality, \the fov set in the game should match the fov that your monitor actually takes up from your vision.
In general with say a 20" inch monitor the screen only takes up like a 45 degree width of your vision. While the game projects for instance an 85 degree game world. This is what makes objects appear twice as small as they are, and makes you think that a distance is twice as long as it is in reality.
(the reason for displaying a bigger fov than your screen takes up is simply that 45 fov, feels like playing with horse flaps on your head like you're viewing through a tiny window.)
I made a small drawing, about how to calculate the fov for obtaining a 1:1 size similarity with reality here:
Here is perhaps a slightly more illustrative picture (note this picture is about vertical fov RO requires you to enter the horizontal fov).
If if you sit closer to your screen things will look bigger, and if you sit further from your screen things will look smaller. Basically there is only one point where things will look at the same size at every distance as in real life.
As a personal experiment try playing a map with the default 85 fov and judge some distances, write them down on paper. Next change the fov using the formula given above and judge the distances again and write them down. Finally open up the map in the map editor and measure the distances. You'll see that when using the fov from the formula above you end up guessing quite well while with the default fov you'll be off.
(you can change the fov in RO only in the singleplayer you do it by typing the following in the console (replace xx with the required degrees of horizontal fov)
-------------------------------------------------------------------
Basically it is all based around depth cues that your brain uses to assume the distance of something.
In this case it is the size of the image projected in the back of your eye, and the knowledge of the size of the object, using that information your brain is able to calculate the distance towards the object.
As humans we are accustomed with perspective, and use that to see how far someone is away from us. By basically looking how big the projected image in our eye is. If someone is double as small then he is approximately double as far away.
And since we've been on this earth for a while we have gotten accustomed with what distances belong roughly to what sizes of people/houses/streets at various distances. This is why in a game you often perceive distances as being further than they really are. Which is especially apparent if you play a game with 3d glasses it ends up feeling like you are fighting against tiny toy soldiers.