First of all I am pulling most of this from: http://dow.finaldeat...DNWikiHome.html
It IS OUT OF DATE, like many, many years and several expansions out of date. But I will be trying my best to update and pull only relevant information from it. Also if there is anything wrong please correct me and I will update this post.
I am going to start with basics of modding, file types and there uses. Understanding this is required for modding.
.SGA - A proprietary compressed file, this stores all game data that can be changed. So anything that isn't controlled directly by the engine.
.LUA - A powerful scripting language, implemented in many games as an easy way to make changes. .SCAR files are based on this.
.SCAR - Scripting at Relic, SCaR files are used to implement game modes and other fun stuff.
.RGD - Relic Game Data (I think), these are compiled version of the attribute data that you are editing. This is what you will be working with for the most part.
.AI - Files for controlling the AI.
.Module - A config file for defining files required for a mod or expiation to load, more details will be in another post.
.TGA - Targa Image files. Note: All TGA files need to be 32 bit, with the alpha transperency layer on, else they will be replaced by pink in game.
.RSH - Texture files requires special tools to work with.
.DDS - Texture files can be edited by standard programs.
.WTP - Texture files, these are uncompressed, multi-layered textures that allow team-colouring for use in skirmish/multiplayer.
.RTX - Texture files, these are compressed, single-layered textures (basically a compiled version of a WTP with a specific colour scheme) that can be assigned to a player in a game via SCAR, or are used in skirmish/multiplayer when team-colouring is turned off.
.WHM - Model files, some one else can give the info on these.
.WHE - Model files, see above...
.SGB - Map files, made with the map editor.
.SCREEN - This is for UI layouts.
.RAT - Relic Audio Tool, sound files round 1, sound effects.
.FDA - Proprietary sound file, sound files round 2, a MP3 like file that requires a particular tool to edit. They are converted from .AIF or .WAV files.
.UCS - Localisation files, these can be used to localise mods without having to mess with game logic.
.NIL - Inherited Game Data, no idea what this does little information on this.
If there are any other files that you find or need information on please contact me.
Edit: Added .WTP and .RTX as per Kasrkin84's information.
Edit 2: Added .UCS files.
Edited by daxx367, 09 March 2018 - 11:23 PM.