Background:

Many people know and love the old school Shadow Boost mod as a solution to Fallout 4's shadow optimization problems. However, with the launch of CC and various game updates the original author seemingly gave up updating it for successive game versions and it's essentially been dormant since early 2017. It's a shame as the only real updates needed to it were basically accounting for new global variable offsets in later executables. Other than that, everything else worked exactly the same. Eventually an alternative mod, Dynamic Performance Tuner, was developed but many still desired for the original Shadow Boost and didn't need the other features that DPT provided and/or thought the shadow distance algorithm wasn't as good for whatever reason.

As a result of my own attempts to delve into FO4's shadow issues I spent a decent amount of time reverse engineering the ASI (it's just a DLL) to determine exactly what offsets it was looking for and what was preventing it from working with the latest version of the game and am happy to report that I've got it working again for version 1.10.163.0 of the game without any issues:



Unfortunately, given that the original author has not given permission to redistribute the mod on Nexus, I can't just reupload it here verbatim. On the other hand, the author hasn't really been interested in fixing it for the latest game version and it's basically sat unused for nearly 5 years. As such I'm simply uploading xdelta3 patches and providing a Google Drive link to the patched version of the ASI if one wants to go that route.

Instructions (short version, you trust that the patched version is safe):

• Download the latest Shadow Boost and copy the contents to your game directory if it's not already installed (ASI loader, ASI, and ini file).
• Download the patched ASI from here and copy it to your game directory, overwriting the 1.9.4.0 version of the ASI.
  

No matter which route, remember to edit ShadowBoost.ini file to set preferred min/max shadow distance and min framerate (note: if you want 60 and have an fps limiter or vsync at 60, use 56-58 as the target). For 60 fps players at near ultra settings, I recommend fShadowDrawDistMin=2000, fShadowDrawDistMax=16000, and fTargetFramerate=50 as a good balance of quality vs framerate for the various problem zones out there. fDistChangeSpeed is fine from at higher values, even up to 8, and mainly controls the how quickly shadows are pulled back or restored when below or above the target.

Instructions (long version):

• Download xdelta3-gui and decompress it's contents to a new directory.
• Download the latest Shadow Boost and copy the ASI file to said directory, renaming it as ShadowBoost.asi.orig.
• Download the patch from the files section of this mod, extract the files to the same directory, open a command prompt, cd to that directory, and run: 
  xdelta3.exe -d -vfs "ShadowBoost.asi.orig" "ShadowBoost Patch file.vcdiff" "ShadowBoost.asi"

• Use the resultant ShadowBoost.asi file (produced by the patch) with the game rather than the original 1.9.4.0 version.
  

Technical details:

• ASI: ASI files are basically just DLLs injected into the game by an ASI loader (xinput1_3.dll) at game startup. One naturally asks: why not just do that with an F4SE plugin? The answer is: at the time the original mod was released (Nov 2015), there was no generic F4SE injection framework available at all so the original author simply repurposed an existing approach from GTA5. The approach in general is fairly straight-forward DLL-injection utilizing a code-cave.
• Compatibility: The injected DLL shims itself along-side an existing game function that's essentially called per-frame and as such is able to make accurate FPS calculations from which to alter fDirShadowDistance directly (the main shadow distance variable that affects the draw distance and hence performance). As such, there are no compatibility issues whatsoever with High FPS Physics Fix, Buffout 4, or ENB itself - in fact I use them all myself, along with ReShade as well.