...
This can be a big pain in the arse. Things like leaves or whatnot. Some notes to follow and check out 4x Texture Upscaling pages for some attempts at formalising it.
Converting to DDS
The intermediary file, usually PNG, could be TGA or another uncompressed format, can be converted using NWN Crunch: https://neverwintervault.org/project/nwnee/other/tool/nwn-crunch-enhanced-edition
There are some reasonable default cmd scripts but some edits are needed for doing:
- Non-alpha using 4096x4096 textures with DTX1 - this compresses a lot better when you don't need that alpha layer
- Converting dimensions downwards, such as making portraits smaller using one base large image
See the SVN for these scripts.
Final DDS should be as close to the original sizes as possible, keeping under 15MB, see Overhaul Models and Textures at the bottom for notes on this but basically with alpha it is usually 2048x2048 maximum and without alpha it is 4096x4096 - although only needed on very large creatures like Dragons or Giants.
Existing Diffuse adding PBRs
...