Fallout 4: Disabling Godrays via Fallout4Prefs.ini for FPS

Godrays in the Creation Engine are rendered using a technique that relies heavily on GPU tessellation. In the vanilla game, even the “Low” setting in the launcher doesn’t fully disable the performance hit in certain weather conditions. By accessing the configuration files, we can set the volumetric lighting variables to 0, which can result in a 10-20 FPS increase in outdoor areas. This guide provides the exact lines needed to kill the rays while maintaining the rest of your lighting quality.

Hardware Compatibility & Expectations

• Mid-Range GPUs: Godrays are the #1 cause of “stuttering” when looking toward the sun in-game.
• Boston Performance: If your game lag spikes specifically when entering the city, this is the first setting you should change.
• Visual Trade-off: Disabling godrays will remove the “dust motes” and light beams seen through trees or windows, making the lighting look slightly more “flat” but much clearer.

Backup and Preparation

Before editing, ensure the Fallout 4 Launcher is closed, as it can overwrite your changes.

1. Exit Fallout 4.
2. Navigate to your Documents folder.
3. Right-click Fallout4Prefs.ini, select Copy, and save a backup copy on your desktop.
4. Open the original file with Notepad++.

File Location

The preferences file is located in your local user directory: C:\Users\%USERNAME%\Documents\My Games\Fallout4\Fallout4Prefs.ini

Best Config Settings

Open the file and search for the [Display] section. Update or add the following lines to completely disable the volumetric effect:

[Display]
bVolumetricLightingEnable=0
bSAOEnable=1
iVolumetricLightingQuality=0
bForceIgnoreSmoothness=1

If you want to keep them but maximize performance, use these “Low” forced values instead:

[Display]
bVolumetricLightingEnable=1
iVolumetricLightingQuality=0
iVolumetricLightingGridResolution=16

Key Parameters Explained

Parameter	Recommended Value	Impact
bVolumetricLightingEnable	0	The master switch. Setting to 0 removes all godrays and the associated lag.
iVolumetricLightingQuality	0	Sets the resolution of the light beams. 0 is the lowest/fastest.
iVolumetricLightingGridResolution	16	Controls the grid density of the rays. Lower values (like 16) are much faster than the default.
bSAOEnable	1	Keep this at 1 (Ambient Occlusion) to ensure the world still has depth shadows.

In-Game Settings vs. Config

To ensure these tweaks stay active, follow these steps:

• Launcher Settings: Do not open the “Options” menu in the Fallout 4 Launcher after editing the .ini, as it may reset bVolumetricLightingEnable to 1.
• Shadow Distance: Set this to Medium in-game. Combined with disabled godrays, this is the “Golden Trio” for stable 60 FPS in Boston.
• Weapon Debris: If you have an NVIDIA card, set this to OFF. It is known to cause crashes on modern RTX cards regardless of godray settings.

Troubleshooting & Common Fixes

• Rays Still Appearing: If godrays persist, you may also need to edit Fallout4.ini (in the same folder) and ensure bVolumetricLightingEnable=0 is present under [Display].
• Pixelated Edges: Sometimes disabling godrays can make the edges of buildings look “sharp” or “pixelated” in foggy weather. Setting Anti-Aliasing to TAA helps smooth this out.
• Read-Only Mode: If the game keeps turning godrays back on, right-click Fallout4Prefs.ini, select Properties, and check Read-only.

Frequently Asked Questions (FAQ)

Conclusion and Expected Results

By manually refining your Fallout4Prefs.ini, you are removing the single most unoptimized feature of the Fallout 4 engine. You can expect vastly improved stability in downtown Boston, higher average FPS during sunset/sunrise, and a consistent experience even on older hardware.