Guide for effective disabling of VSync / Mouse Acceleration / X&Y uneven sensitivity

[Jisker91]

Found this on Reddit and it works excellently. Makes the game run and play a lot smoother.


https://www.reddit.com/r/fo4/comments/3s6ile/disable_vsync_for_zero_input_lag_and_limit_fps/


Ok so as you may know the V-Sync in many games is splendid for eliminating screen tearing but often introduces input lag/mouse lag in game which is probably my #1 pet peeve in all gaming, especially FPS games.
In Fallout 4 (and any other Bethesda game on the Creation Engine) V-Sync is forced on with no option to disable it without editing the config files. Problem is the physics engine is tied to your FPS so disabling V-Sync thus increasing FPS over the set limit can cause allsorts of undesirable consequences. In Skyrim it caused serious issues (dat bumpy cart ride) and in Fallout 4 it seems to mess up lockpicking, accessing terminals and other things.
By default Fallout 4 uses adaptive V-Sync (i think it's this one) which limits your FPS to half of your monitors refresh rate. For example i have a 144hz monitor so with V-Sync on i'm limited to 72fps max at all times.
So we want V-Sync disabled for better input "feel" (and trust me after doing this it's worlds better) but we don't want to mess up the physics by letting the framerate get too high. Onto the guide.

Disable V-Sync
1) Go to your fallout4 folder in documents, mine is located in "C:\Users\Ash\Documents\My Games\Fallout4\"
2) Open Fallout4Prefs.ini with your preferred text editor.
3) Find the line iPresentInterval=1 [1] and simply change the 1 to a 0.
4) Save the .ini and close the file.
Limit the framerate
1) Download and install MSI Afterburner[2] . Then launch it.
2) Open RivaTuner [3] , located in your taskbar.
3) Add Fallout 4 by clicking this [4] . Find where it's installed on your PC, for me it's "D:\SteamLibrary\SteamApps\common\Fallout 4\fallout4.exe"
4) Use this option [5] to limit your FPS. I've set mine to 72 as i don't seem to have any odd physics issues with it capped at that but you could try 60, maybe even 100+. Not too sure what the game has to hit before it has problems. EDIT: Make sure your "Application detection level" is set to medium or higher or it may not work! Thanks to /u/seeberger48 [6] for noticing this

Disable mouse acceleration
I'm not entirely sure this works but I've seen it mentioned a lot so worth a shot. In the same file you edited "ipresentinterval", under the controls part of the .ini add this:
bMouseAcceleration=0
And save.

Make the X&Y sensitivity even
Presumably an oversight unchanged on PC as it's more of a console benefit, the up/down look sensitivity is halved when compared to your left/right sensitivity. To fix this go back to your my games/fallout4 folder but this time open fallout4.ini, not the prefs one.
Under the controls section you should see two similar lines of code, fMouseHeadingYScale & fMouseHeadingXScale. You need to double the value for Y that you have for X to get "1:1" mouselook.
Save the file. I assume that if you then ever change your sensitivity ingame it will reset this fix so either don't or set the file to read only.
If you've followed the steps correctly when you launch Fallout 4 and get in game you should be limited to your desired framerate without any sort of input lag. Hopefully i've been clear enough in these steps but if not just let me know!

[Jisker91]

Originally posted by Gigabyte:

Can we limit the frame rate by using the nvidia control panel?

I'm not sure. I originally disabled VSync through the control panel but it made the game run way too fast and I got stuck after using a terminal.

[🦊Λℚ𝓤ΛƑΛᗯҜᔕ🦊]

NO NO NO NO NO NO!!!!!! This game's physics engine is tied to the FPS. You never ever ever under any circumstances release the vsync lock or you get all those retarded errors (stuck on consoles, stuff flying around, etc). The frame rate absoultely must remain locked at 60 FPS at all times in this game or it will not function correctly. There is no if's, ands, or butts about it.

[Jisker91]

Originally posted by Impending Rentacle Tape:

NO NO NO NO NO NO!!!!!! This game's physics engine is tied to the FPS. You never ever ever under any circumstances release the vsync lock or you get all those retarded errors (stuck on consoles, stuff flying around, etc). The frame rate absoultely must remain locked at 60 FPS at all times in this game or it will not function correctly. There is no if's, ands, or butts about it.

That is wrong. If you have a 144hz monitor the game will cap it above 60 to 72 due to the adaptive vsync. The game will not feel smooth though. This way with the vsync removal and manual FPS cap it runs perfectly.