At present, loading the ReShade DLL's from the root path of MHW for DX12 has been disabled by Capcom whether this was intentional or a mistake, it's managed to  break ReShade loading.

After a couple of days, the ReShade author has stated that they will not be fixing this as it's not something they cover but has provided an alternative way to "inject" the DLL into the MHW process, it is a bit tricky to do unless you know what to look for and set it up, which got me to creating this. 

Current version of ReShade is 4.9.1

Installation:

• Download and extract the executable to a folder location of your choice (can be the MHW directory if you wish)
• Run the MHW - Reshade Injector Helper.exe to make sure the ReShade is loading for your game properly, and sets up the necessary files for it to load
• Press "Home" whilst in-game and set up your shader/texture/screenshot location to your previously installed locations (most likely the MHW folder)
  

Effect Search Path should point to : \reshade-shaders\Shaders
Texture Search Path should point to : \reshade-shaders\Textures
Screenshots wherever you want these to be saved to if you use this functionality. 

If you need a screenshot guide, there is a documentation file in the optional files section which can guide you through all of the above.

Uninstall:

Delete the executable, ReShade64.dll, ReShade.ini and inject.exe.

Usage:

This mod assumes you have already used ReShade before or already have your game setup for ReShade, if not please install ReShade (https://reshade.me/) with it's included shaders and ignore the next instruction.

To use your already made ReShade configuration, in the MHW Folder (mine is found on C:\Program Files (x86)\Steam\steamapps\common\Monster Hunter World , yours may vary) find either dxgi.ini or d3d11.ini depending on which version of D3D you have used and copy this to the same folder as the provided ReShade.ini that is created once the .exe has ran atleast once, delete ReShade.ini and rename your dxgi.ini/d3d11.ini to ReShade.ini (it won't be replaced by the mod's version as it is only created if there is none present)

This will then automatically pick up your current reshade settings, along with your effect search path, texture search path and screenshots. Also, your default presets etc. 

The MHW - Reshade Injector Helper.exe loads a file called inject.exe with the argument to look for the MonsterHunterWorld.exe and then asks steam to run the MHW Game. You can find the source code at https://github.com/keegars/MHW---Reshade-Injector-Helper/tree/0.1

The Injector is found at this site, if you wish to set this up manually : https://framedsc.github.io/ReshadeGuides/reshadeuwp.htm

Notes

The executable (MHW - Reshade Injector Helper.exe) will need to be ran EVERY time you wish to have ReShade run with MHW. You can use it as a launcher for MHW, as it uses steam natively to load MHW, so game time, overlay etc will still load as normal. This has also been tested with strackers loader, which is compatible. 

Virus Total Reports

This is for those interested in checking that there are no virus' with any included files:

ReShade64.dl - 0 Detected
https://www.virustotal.com/gui/file/93c9578f65b4bc0f6b65131ea2d5862605ce7d2fd7a84aa98ac74f3ef610bb7d/detection
Inject.exe - 0 Detected
https://www.virustotal.com/gui/file/0281df5cf73c1101bcb5f873d41bd966f2b565ea1d5c3813023920185de3fcc5/detection
ReShade.ini - 0 Detected 
https://www.virustotal.com/gui/file/b643537212952f65aca47e8f1e0e79f97c8f8dd20cf3ffc8c47c1e05d4ded068/detection
MHW - Reshade Injector Helper.exe - 0 Detected
https://www.virustotal.com/gui/file/7520cb9170fca0f01f643c5fe5661f39421ea8d120a1e8fd2e8a387db6e7d3cc/detection

Remember - Source code for the executable is available at https://github.com/keegars/MHW---Reshade-Injector-Helper


Credit:

ReShade - https://reshade.me/
FramedDSC - https://framedsc.github.io/ReshadeGuides/reshadeuwp.htm
Corsire Injector - Reshade Injector