Open your nightfiresource/cfg folder (C:\Program Files (x86)\Steam\steamapps\sourcemods\nightfiresource\cfg)
Open the autoexec.cfg file
Add this at the end:
r_dynamic 0
mat_bumpmap 0
mat_specular 0
r_waterforceexpensive 0
mat_bumpmap 0
mat_specular 0
r_waterforceexpensive 0
NOTICE: If you only have FPS problems on Japan, simply use the r_dynamic 0 command above and ignore everything else. Your fps problems should then be solved
These commands above will disable dynamic lighting (such as gunshot light and physics lanterns), high quality water, reflections and pseudo-3D texture mappingIf your FPS still suffers, you can force run the game in DirectX 8.1 mode by following these steps:
Rightclick on Nightfire Source in Steam. Click Properties. Click "SET LAUNCH OPTIONS..."
Add -dxlevel 81 and then click OK.
Start Nightfire Source. After getting to the main menu, close the game and remove -dxlevel 81 from the launch options.
Start Nightfire Source again and change your video settings again in the options as changing directx will have reset your graphics settings.
To revert to DirectX 9.0c, repeat the above steps except use -dxlevel 95