This tutorial is intended for those that already have a vague idea on using Gimp, but are not actually good at it because otherwise they`d be able to make more sophisticated stuff than the ones described bellow.
1. First of all open the texture you want to make gloss for. I`ve chosen a late roman cataphract cavalry for the example:
2. Now you need to remove all the parts that are not metal from the texture and leave only those on which you want the gloss to apply to in game. If you don`t know how to use the select and cut tools please consult some of the already existing tutorials for skinning with Gimp or making ui cards with it. You may want to avoid including parts like mail armour or painted metal because normally those shouldn`t reflect the environment imo, but ultimately it`s up to you. Anyway, in my example I was left with something that looks like this:
3. I advice you to save this file as a .tga because it may help later. If you`re gonna do gloss for more than one unit you may find that other textures(maybe variations of the same unit) have pretty similar metal parts and you`ll be able to use part of your previously completed work. Before saving the file hit Ctrl+L which will open the layers panel. You need to remove all the existing mipmaps(don`t delete the main surface though). This will help later when you`ll need to save the result in .dds format for the gloss file.
4. Now go to Tools->Color Tools->Hue Saturation...
and move both the lightness and saturation bars to the far left(i.e. -100), leaving the hue bar as it is on 0.
5. Go to Layer->Transparency->Color to Alpha...
and click on the white box that`s between From: and to alpha.
On the new panel that appears you need to change the color from white as it is by default to black so that the HTML Notation is 000000.
Click ok to apply the change. You will get something like this:
6. Now save this file both in .tga and in .tga.dds format. Considering that the name of the original texture was in the example:
Equites_Cataphractarii_west.tga.dds
the gloss files should be named like this:
Equites_Cataphractarii_west_Gloss.tga
and
Equites_Cataphractarii_west_Gloss.tga.dds
Because the gloss files are taken by association with the texture without being mentioned in the text files themselves, they need to contain the name of the texture.
Finally, place the two new files in the same folder where the texture is and if the video option for gloss is checked in your game you`ll see the result. For example:
before:
after:
before:
after:
This is obviously a pretty rudimentary process and the gloss can be further adjusted according to taste, but for a beginner, this should get him started.