Posted by Illume on the NMS Modding Discord:
"A guide on how to extract missing DDS textures from NMS if they dont import properly into blender.
Step 1 : Install Intel Texture Works. (https://software.intel.com/en-us/articles/intel-texture-works-plugin) Used to read NMS DDS files in photoshop SageThumbs (https://sourceforge.net/projects/sagethumbs/) Able to preview weird custom photo formats
Step 2 : Reboot your pc
Step 3 : Open the DDS files and enjoy!
If you cant afford photoshop or dont pirate software.
Step 1 : Install all programs listed below Paint.Net (https://www.getpaint.net/) Free Open source photo editing software SageThumbs (https://sourceforge.net/projects/sagethumbs/) Able to preview weird custom photo formats
Step 2 : Once installed go to paint.net directory and install the DDS Filetype. Paint.Net DDS Addon (https://github.com/dtzxporter/FileTypeDDS) Allowed Modifation & editing of NMS DDS files
Step 3 : Reboot your computer to make sure everything is properly installed
Step 4 : Once logged back onto your pc open Paint.net
Step 5 : Go to File > Open > Pick your intended DDS Files or Press Ctrl + O > Pick your intended DDS Files. Step 6 : Edit files if need be Step 7 : File > Save As > Select File type output > Save or Ctrl + Shift + S > Select File type output > Save"
Terrain texture formats:
Diffuse - 4-bit DXT1, compressed with 1-bit alpha
HSV - 4-bit DXT1, compressed with 1-bit alpha
Normal - 8-bit DXT5, compressed with interpolated nonpremultiplied alpha