As you may have guessed, Photoshop is the weapon of choice for this. The primary issue that you will have with it is trying to find a program that can output/edit them. TARGA is an old weird image format, it has plenty of nice features, but has been mainly overtaken in most industries by PSD or PNG files.
jpgs/.pngs can’t be used without conversion. The most important factor is that the dimensions of the image must be a power of 2, (i.e. The internal data is organised in a way which is most efficient for rendering, this is why normal. They are created by converting an existing image file using a special program. The VTFĪ VTF (.vtf) file contains all the pixel data, alpha maps and mipmaps that a texture can use. Both are used together when displaying a texture in the games. Textures are split into two files: the VTF ( Valve Texture Format), a file containing the image data, the pixels of your texture, and the VMT ( Valve Material Type), a file containing metadata and shader details about the texture. Unlike modern engines, there is no “ drag and drop, and it just works” here, you must do most of the work yourself. Creating textures is not an intuitive process, but not an overly difficult task either.