Character textures are stored within their respective directories. For example, if you're looking to modify one of Lightning McQueen's textures, go to C/Global/Chars/McQ/Tex and open the .DDS file.
In order to make the file to work in the photo editor you'd like to use, you may need to convert the file to a more common format, such as .png, as many photo editors can not open .DDS files. Should you convert your file to another format, you must then convert it back to .DDS format, so that the game will be able to read it. http://image.online-convert.com/ is a recommended tool for managing conversions.
Once you're finished, you will need to add additional data in order to add it to the game. This includes:
- A .XNM material file that matches the name of the texture so that the game will recognize the texture. The car models actually search for these files, which in turn point to the textures, instead of searching just for the .DDS files.
- A new listing in the VehicleInfo.dat under the respective character's name. Let's use Fred as an example -- you would need to add a "PaintJob = fred_b" under the "PaintJob = fred_a" line. Then create the entry itself; you would put in the following text:
- Locked = FALSE
- Material = [the name of the .XNM file]
- You will also need to list the .XNM material in the "Chars.X360" .mst file found in C/Global/Chars. Using Fred as an example again, find Fred's section of listings, and then write C/Global/Chars/Fred/Tex/[name of .XNM material]
You could also replace an existing texture but it's much more fun to have more than one paintjob for each car.