[GUIDE] Finding the Mathematically Correct FOV & Multimon Settings For ANY Monitor Setup

[a1337cookie]

@Foxman

Following the procedure for perpendicular matching monitors, with monitor width 714mm, screen width 700mm, and monitor angle 50°, you should have a horizontal_fov_override of 50 for all three monitors, and the subrect settings are as you stated. To shift the side monitors closer to the center, you would increase frustum_subrect_x for the left monitor, and decrease it for the right monitor. However, the value must stay between 0 and 0.019608 (1 - frustum_subrect_width). A frustum_subrect_x of 0.019608 for the left monitor would remove the left bezel correction; a value of 0 for the right would likewise remove the right bezel correction.

Unfortunately though, that likely won't be enough. There is still bezel correction on the center monitor. You can try remove all bezel correction by resetting all subrect settings to their defaults (0 for x and y, 1 for width and height) on every monitor, but it will alter the FOV slightly, making it less mathematically correct. If it still doesn't line up, and you need negative correction, then some additional adjustments must be made.

Now, there's no single right way to do this, as mathematical correctness won't be maintained. The idea is to alter the FOV and camera angle as little as possible, while making sure the edges still align. If we're trying to maintain the correct view for the center monitor at least, then we would keep the same settings that you first calculated, and shift the side views closer. The horizontal FOV of each side monitor will have to be increased, then subrect width reduced to compensate. That will allow subrect x to be increased/decreased to create negative bezel correction. Just have to make sure the vertical FOV is the same, so the edges line up, and maintain the aspect ratio, so the whole image is not stretched.

Try the following settings for the side monitors.

• horizontal_fov_override: 52.0
• frustum_subrect_width: 0.937326
• frustum_subrect_height: 0.937326
• frustum_subrect_y: 0.031337

Then, adjust frustum_subrect_x (must stay between 0 and 0.062674) until it looks right.



As for sitting distance, just a reminder that the procedure for perpendicular monitors is intended for when your head is perpendicular to all monitors. That means, when you look at the center point of each monitor, your line of sight should be at right angles to the surface of the screen. The exact distance the perpendicular point is can be calculated; this formula is from the perpendicular mismatched section.

y = x₁/(2tan(A)) + x₂/(2sin(A))

It comes out to about 765mm for your current setup. So if the center of your head is around that distance away from the monitors, it should be about perpendicular. With the 60° monitor angle you had before though, the distance would be closer to 620mm, which is why I thought you were sitting too far away.

[Foxman]

Thanks heaps mate, really appreciate you crunching the numbers. I am quite happy to accept that the solution is not going to be perfect but getting it close will hopefully make the end result largely unnoticeable when everything is in motion.

I'll take those numbers as the starting point and tweak the appropriate x value to see how well I can get it to fit. Will report back with results once I've had some time to experiment :D

[MrPapaBear]

So why use this and not the ingame FOV slider?

[a1337cookie]

@MrPapaBear

I believe the in-game slider is inaccurate. Using the same numbers for FOV override in the multimon file does not produce the same result, at least for my triple setup.

If you mean why go through the trouble editing values in the multimon file rather than just adjusting the FOV in-game, it's because the in-game settings are very limited. There's more to it than just FOV, you need the multimon file to control the camera angle and frustum subrect settings. Each view can also be customized separately. It enables the configuration to be more mathematically accurate.

Of course, it also depends on your setup. If you just have one monitor, perhaps you can get away with just using the in-game adjustment. The point of the post is to be mathematically accurate though, so it's best to use the multimon file.

[MrPapaBear]

Oh this was not criticism, I find it Interesting using the Multimon would also give me the chance that i don't have to change it all the time again when buying a new truck and so on. I was just curious, that's all.

[a1337cookie]

@MrPapaBear

No worries, you asked a good question. Just wasn't sure what you were referring to when you said "why use this", haha.

[MrPapaBear]

Could u do your Magic pleases, Math is not my strong subject i think we are at war with each other.
So my Monitor is 53cm width and 30cm high without the bezels and i have a Eye to Monitor Distance of 83cm. What would be the correct Numbers for the hFOV and vFOV? I used a online calculator(3different ones and your formula) all gave me some different numbers and it just doesn't feel right in Game. For your Formula i have to say too i could have messed it up, I'm not good in this kind of Math.

In Game I see the Top of the steering wheel and have to look down to see any of the Instruments. The numbers i got was 36hFOV and 21vFOV with different calculator's it was +/-5

[a1337cookie]

No problem, math is definitely challenging for many people, I've had my fair share of struggles too.

With given values of screen width 53cm, screen height 30cm, and eye distance of 83cm, my formula should give an hFOV of 35.414185, or vFOV of 20.488175. Note that you only need to use one. In the multimon file, override either the horizontal or the vertical FOV, and leave the other one at 0. I would not know why different calculators give different results, perhaps they try to compensate for certain things or apply some rounding.

With just 35° hFOV on one monitor, it will be very tight. But, if you imagine your monitor as a window into the game world, that is what you would see if you were sitting at that distance. It should be mathematically accurate, though practicality is a different story. I have some ways of compensating for low FOV in the miscellaneous section, give those a shot if you'd like. Let me know if you need help with that.

If it's still too impractical, there's no choice but to increase the FOV. To stay mathematically accurate, you can move closer to the screen, or get a bigger screen. However, if those are not an option, then just use whatever FOV is most comfortable for you, even if it's not "correct". The end goal is to have fun after all.

[MrPapaBear]

I did as you recommended And its getting way better. I used the vFOV. So to adjust the eye level upwards to see the dashboard. What would you need to calculate this and what would I need to change in the Multimon that's the part that's really complicated for me to understand. My Monitor is at a 0 degree Angel to me, if you need to know that.

[a1337cookie]

For your case, you just need the eye distance and the height of the screen. Then, you must choose how high you want to shift your eye level. I use "normalized vertical displacement" in my formula, but it really just means "how many screen heights to move up by". Try starting with a value of 0.25, which means shifting the eye level up by 25% of the screen height. Inserting the numbers into the formulas, we get:

v = 2arctan((0.5+0.25)(30)/(83)) = 30.334932

and

s = 1/(1+2(0.25)) = 0.666667

Then, in the multimon file, you would set vertical_fov_override to the value "v" we found above, and frustum_subrect_width and height to the value of "s". Also set frustum_subrect_x to (1-s)/2, which is 0.166667. Finally, since our eye level shifted upwards, set frustum_subrect_y to 0. (There's a mistake in the instructions, the values are flipped. It will be fixed in the next update.)