https://forums.dolphin-emu.org/Thread-fatal-frame-iv-mask-of-the-lunar-eclipse-hd-texture-pack

Disclaimer:
this Texture Pack will only work with the Original Japanese Disc that has been Hard Patch with the English Fans Translations Patch

Link to English Fan Patch:

https://archive.org/details/fatalframe4eng/

Download the Texture Pack from the Link Below
Download Dolphin if you haven't already.
Extract the folder R4ZJ01 to \Documents\Dolphin Emulator\Load\Textures\
Double click Dolphin and click on Graphics then click on Advanced make sure Load Custom Textures is checked.
For better performance make sure Prefetch custom Textures is checked (32GB or more RAM is recommended)
Click on Graphics then Enhancements (If you're on Advanced you just have to click on Enhancements) and set your internal resolution to a higher value. 2x (720p) 3x (1080p) 4x (1440p) 6x (4K)