*.thm
About
They are used to set the parameters of *.dds textures - *_bump, *_detail, and more. Without them the game does not give textures the necessary parameters, and therefore they are obtained "flat", worse than the static lighting.
Programs
THM Editor by ValeroK
The THM Editor from i-love-kfc was taken as the basis, finalized and fixed. Allows you to work with .thm files.
THM Editor by i-love-kfc
Utility for editing *.thm files without the need to use the SDK.
IX-Ray SDK
SDK or Software Development Kit helped the developers of the original trilogy and the modders to develop the game itself.