Concepts: renaming textures in the model before it's exported, making sure the textures in the model matches those in the base txd, and adding new "skins" to the img.
It's assumed that you already have working knowledge of the application your vehicle is being modeled in, as I will not cover any program-specific info here. Also, a general knowledge of gta:sa modding will help immensely, particularly the addition/replacement of txd's, and dff's in the img.
Synopsis: diffuse textures for skinnable body textures of vehicles need to be named "remap<whatever>" in order to work with the "skinning" system in place in the game. The "remap" part of the name, is necessary, as this is what the game uses to identify textures that are "skinnable". Skinnable textures are actually swapped out with other textures, your paintjobs, when the car is "painted". Where <whatever> is, you can put the rest of your car name. I like to name my texture that is to be skinnable using this format; "remap_<carname>_body", so for the Chevy Caprice I made, it would go something like this:
The "remap" part of the texture name is crucial, as this is what the game looks for when it swaps textures, so be sure you don't forget it.
As far as I can tell, there is only one "skinnable" texture allowed per vehicle. You can however use that one texture in multiple materials. This technique is non-application specific, so if you're working with Lightwave, 3dsMax or Zmodeler, the instructions (to follow) are essentially the same.
Once you have named your texture correctly and applied it to the vehicle you are working on, you can export that vehicle to the game. From there you will be adding new txd's to the IMG, so the game actually has "skins" to use on your vehicle.
Here are the instructions so far, for model and txd preparation:
1. Load up model to be "skinned". It is assumed that the model is ready at this stage. Ready would mean fully uv-mapped, at least for the "skinnable" texture you are going to give it.
2. Take the texture you are currently using for the body, make a copy of it, and re-name it using the rules outlined above. Again, "remap<whatever>" needs to be its filename, plus the extension (tga, bmp, etc).
To make a copy of a file, simply select the file in windows, and press ctrl-c on your keyboard. this will create a copy your currently selected files.
Now press ctrl-v, to paste them into your folder (whatever folder your in). It will add the prefix "Copy of " to your filename.
To rename the file, select the copy, and right click on it. Choose "rename" from the pop-up menu that appears when you right click;
this will select the text of the filename...
and you can rename it, as i show here...
Don't change the extension though, which is the last 3 letters of the filename (.tga in my case).
3. In the material editor of your application, find the material you are using for the body of your car, and replace the old texture, with your newly re-named one. If your vehicle was imported, and there are multiple materials for the body, say one for the doors, another for the hood etc, then do this for all of them. Every part you want to change with your paintjob needs to be using the re-named texture.
4. Tha's basically all you need to do to the model. Export the dff, and open or create the base txd for the vehicle.
5. Once you have the txd for this vehicle open, find the texture you were using for the body, and re-name it, to reflect the changes you made on the original file. So again, if the original body texture was caprice_body, and you renamed it to remap_caprice_body, then make the same name change to the appropriate image in the txd. Save the txd when done.
6. Replace the txd and dff for your vehicle in the IMG at this point, go ingame, and make sure everything is tip top. If it's all working out (car loads, with base body texture), then proceed to the next phase, which is making actual "skins"ï¿½ for the car.
Car Skin creation and addition
Bad news out of the way; each car can have no more than 4 skins, period. It's a hard coded limitation to the game that cannot be changed.
The game will automatically find the skins for your car as long as the txd's that contain the skins for your car, are named correctly. The main txd for your car, should simply match the name i.e. bobcat.dff, and bobcat.txd. The skinnable version of the txd, will have to be renamed bobcat1.txd. you can add up to 4 "skins" per car. Example, the game will not load any bobcat skins past bobcat4.txd. It's a hard coded limitation I'm afraid, and cannot be increased.
Txd (Skin) Preparation:
1. So take the txd for your vehicle, and make a copy of it. The same process as copying the image is used here.
2. Re-name the copy to <carname > 1.txd and open it in txd workshop.
3. Delete all the textures but the body texture.
4. Rename the remaining body texture by removing the "remap"ï¿½ from the texture name for the skin. Only the base texture needs to be named that way, not the actual skins. Save the txd.
5. In Windows, Make a copy of your body texture, and rename it to match the renamed skin, in your <carname>1.txd
6. Open the renamed body texture, which is going to be your first skin, into any image editing program, and make a noticeable change. Doesn't matter what, just something that will be an obvious change when you "skin"ï¿½ the car. Change it, save out the image. Close image editing app.
7. Take the newly saved skin texture, and import it into your <carname>1.txd, as the new skin. Save the txd.
8. ADD this txd you just created, to your gta3.img, and be sure to REBUILD THE IMG when you have. Also if you haven't already, be sure to import the updated dff and txd for the regular version of the car as well, since this will require them to work properly.
The game will auto-detect if your car has a skin or not, you don't need to edit any other external files. Go to a mod garage and test it out!!
-You can use carcols (different colors for the car body) on the main body, but you cannot use them on the skin. Its one or the other, there is no carcols-compatible skinning system. ONce the car has a skin, it's coloring will be derived from the "skin" texture.
-Same for the car "dirt". Either your car can get dirty, or you can make it skinnable, but there is no way to make the car use both at the same time.
-4 custom skins per vehicle is it. No more.
Suggestions? If you found this helpful, excellent. If not, please state specifically why, and I'll see what I can do to improve it.
If you had trouble, let me know what step you got up to, and I'll try to help if I can.
Edit: Draft 1, 8/13/2005