Im not a modder, but i know the "old" process of doing things, long before Illusion started to use unity.
I dont have Koikatu at my disposal right now, but Ai-Trial, and did some quick testing - with success.
since the process should be the same for Koikatu, i will try to explain it using Ai-Trial.
Clothing (and other thigns) are located in:
abdata/chara (and abdata/chara/trial for AI-Trial)
Dont forget to make backups first!
In that folder, there will be a bunch of archives that end on
"unity3d", these can be opened with
"SB3Utility" - which is in your "Tools" folder, but only if you got the Repack from Screwthisnoise, otherwise you need to get it from somewhere else. (old versions may not work with new games.)
I then opened the
"fo_top_00.unity3d", which contains the blue-ish camisole in the trial version and the standard one. (Archives can contain multiple things at once!)
Now it gets a bit more complicated, since some files exist twice, and i didnt test what the game actually is using, or if they are referenced by different clothing pieces. (whatever is the case, dont expect illusion to do things conciously, expect weird stuff.)
But in general, thats what it will look like (im not sure about the "wet look" anymore, it was just a quick assumption):
View attachment 432738
The particular texture i have chosen here (to test a theory i had in mind for a while now) contains the following information:
1: The see-through-ness of clothing when wet - its the Alpha-Channel of the image. (cyan is base color here)
2: The "damaged" state of the clothing that you can set in the character editor - its the green channel.
So, the "rules" for this texture in the game are as follows (from what i observed when playing around with it, may be wrong.):
1: More trasparent areas will "break" before the "green area" actually reaches that point. (may also cause the "wet look", cant test it right now)
2: the "green area" is the slider you control in the game.
So, if we now add several stages of "green to cyan" from the bottom of the image to the top, it should allow us to use the "tear" slider to actually determing the clothings length.
And it worked:
View attachment 432757
I used straight lines for my quick test, but any other pattern should work too.
Pro: We dont need 20 different shirts with different lengths as mods anymore
Cons: it overwrites the "broken clothes" pattern Illusion made. (And it might be nasty to add if the texture also contains the "wet look".)
This just as a basic idea, i cant explain all of the things, and how they go together without actually having the game, but from what i saw now, things are mostly the same as they have been 12 years ago, just with more textures.
Important: Textures are encoded as .DDS (DXT5, BC3, linear) <- for Ai-trial, but koikatu wont be much different, i think.
Now its your turn, create backups, play around with Koikatu (or any other game, it works the same as a decade ago.)
There never was a proper tutorial to begin with, and everything that i know, i have found out by trial and error.
For Meshes, its pretty much the same, just more complex and that you need additional Programs. (Blender, or metasequoia for older games)
Oh, and before i forget it:
Illusion tends to do stupid things, have weird structures and many things double.
To me, it seems that they dont really know properly what they are doing, as a lot of these things should be done differently, but at least they are improving now.
Examples: "Tear" could just be a seperate greyscale texture applied to the material via a float (the slider) and it would be easier to maintain for them, and mod for us. (they could even allow the game to acces user-content in the games folder, so that we could just drag/drop our own patterns in there... meh)
*looks directly at the actual modders...* make it happen?
I also dont understand why we have the exact same texture twice, i checked, they are identical. (but that has happened in the past too, nothing new in illusion-land.)
Here are the original texture, and the sloppy edited one:
