ok as far as I’ve read, i havent found an answer yet suitable for what I need. I have a tree texture map that I need an alpha channel for. In maya I can use a separate file for the black and white transparency but in Unity it doesn’t work. HOW do I use a separate file for alpha channel?
You don’t, you just put the alpha map in the alpha channel (using Photoshop or whatever). Although technically you can write a shader that uses a separate texture for alpha, but there’s no reason to, and a good reason not to (namely less memory usage).