This is not a mod. Is a reference page of FALLOUT3.INI settings that can fix issues and or improve the game.  Please post any tricks you know and I will add them here. I believe all these settings can be set from within the game by opening the console ant typing SetGS <settingname> <value> where <settingname>  is name is FALLOUT.INI setting and <value> is the value you wanna give it for example SetGS fScopeScissorAmmount 0. Setting them in game mode only does it temporarily for that game session so you can try it out wether a command works or not. 

Before you make any permanent changes make sure you backup FALLOUT.INI just in case. The engine is buggy and old and is kinda finicky. Experiment with these  and if you discover anything post your finding in the comment section.

not yet in file:


if you got an old machine this may help a bit by skipping frames or reducing frame rate makes the game run smooth at the expense of some skippy visuals only when game is overloaded. Thanks to Timmster for this tip. 
[Display]
iPresentInterval=2

this value is weird do not change will make the world faster or slower or even crash the game if you howevr manage to find an optimal value will make the game smoother
[General]
iFPSClamp=0 ; i recommend not touching this 


you can change level of hacking 
[Hacking]
fHackingMinSkillVeryHard=100.0000
fHackingMinSkillHard=75.0000
fHackingMinSkillAverage=50.0000
fHackingMinSkillEasy=25.0000
fHackingMinSkillVeryEasy=0.0000

these values control grass and wind on grass. For wind speed the values are also controlled in the engine by weathers/climates. So when is raining the wind would be higher (there is no rain in fo3 but the settings are there) so from my experience this is the default no wind ..then this is added or multiplied? to the values set in weather. Also wind speed is not designed for high values so it moves funny if you set them too high
[Grass]
fGrassWindMagnitudeMax=125.0000 ; wind  high values will make the grass move funny (not a bug or glitch just how it is)
fGrassWindMagnitudeMin=5.0000 ; wind
iMinGrassSize=100 ;  how much grass there is...lower number is more higher number less. vanilla is 80
bGrassPointLighting=0 ; makes nicer looking light on grass

if you wanna see yourself bigger in the races menu experiment with this value
[RenderedMenus]
fRaceSexMenuScale=0.5

to disable screen splatter 
[ScreenSplatter]bScreenSplatterEnabled=0

To change FOV of pipboy .
[Display]
fPipboy1stPersonFOV=47.0 ; small number pipboy bigger closeup, bigger number smaller pipboy farther away hand more visible
(Note you can also change the game FOV from a different setting which is not displayed here but i do not recommend it. )


in readme: 

TO make NPCs use ammo. This one is tricky because NPCs get very little ammo and no melee weapon. You need a mod that adds a melee weapon and way more ammo for ranged NPCs for this to be fun. 
[Combat]
bForceNPCsUseAmmo=1

To disable the gray left/right overlays in large scopes/binoculars:
[Display]
fScopeScissorAmount=0

To disable mouse acceleration
[Controls]
fForegroundMouseAccelBase=0
fForegroundMouseAccelTop=0
fForegroundMouseBase=0
fForegroundMouseMult=0


To improve game performance on multicore systems you need at least these minimum settings.  There is a more complex way of doing this which involved assigning threads manually. I don't recommend doing this unless you really know what you are doing! What these do? First you assign two working threads iNumThreads=2 The threads are same as the number of cores. So 4 cores is iNumThreads=4. Then you give it double the threads as havok threads (for 3D rendering ) iNumHavokThreads=4. This last setting is tricky. Experiment with a number between double the cores/threads but no less than that. Then bUseThreadedAI=1 makes AI threaded improves FPS dramatically. 
[General]
bUseThreadedAI=1 ;MUST HAVE
iNumHavokThreads=4 ;experiment with an whole (no decimal point) number between iNumThreads and iNumThreads x 2 (ie 2 ,3, 4 in my case) but apparently most stable is making is same as iNumThreads unless your computer is really fast and has a lot of memory

[Havok]
iNumThreads=2 ;MUST HAVE (this is same as the numbers of cores your computer has ..mine is dual core so 2..quad core 4 etc etc)


To disable essentials from the game (ie make everyone essential killable) NOT RECOMMENDED
[GAMEPLAY]
bEssentialTakeNoDamage=0 ; don't do it!

Help reduce texture flickering. Sometimes when one texture overlaps another texture for example a wall overalps a similar wall you can see this flicker back and forth between the two textures. Is called z-fighting as in they are both fighting to be seen and z is the layer order which in this case is the same as they are both using same textures as they are two of the same objects in the game. I personally have seen this many times. 
[Display]
fNearDistance=8 ;default is 5 but anything over that helps ..setting this too high will make you see thru walls when walking close to a wall..setting it really low might make you see things better when closer


To enable built in laser sights for all weapons. The laser sights look like garbage because probably the texture is crap or missing or the beams are genrated. All enemies will have lasersights and you can see the rays being cast from their weapons. 
[Combat]
bLaserSights=1


To get a bit more FPS you can disable eye environment mapping ,  face mip maps  and face normals manipulation. 
[General]
bUseEyeEnvMapping=0 ; makes eyes reflect the environment. more realistic eyes if 1 ..a bit more FPS if 0
bFaceMipMaps=0 ; engine uses mipmaps to simulate face different face texture like aging  ..textures do a better job than this so 0 is more FPS
bFixFaceNormals=0; the engine fixes normals to simulate face different face texture like aging  ..this  is default 0 so is good


To speed up the menu loading change this setting. Once you start the game usually you just wanna load from where you left off  but the game preloads the intro section every game load. This reduces the load time of the game menu and reduces initial lag on some systems. 
[General]
bPreloadIntroSequence=0 

If you want to travel past the borders and not get the message you can't go in that direction. Be warned though. Going really far past the borders will make the game crash. Also if you go around the border just a bit past there's nothing there . 
[General]
bBorderRegionsEnabled=0 


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