First time trying to do this...
I rendered my character in Maya, and in a separate pass rendered the hair with a black surface shader assigned to the character, and additionally rendered the character alone with the surface shader to act as an alpha?
Unsure of how to put this together in AE, a suggestion was to use the hair and alpha and use blend mode of difference?but doesn't work, so any suggestions please?
Sorry forgot to mention that I'd also tried that and i get one of a few results, either the hair with a black torso, OR nothing, OR the outline of the hair up until the outline of the scalp, OR the hair excluding beyond the outline of the scalp.
Tried adding the last 2 together and still end up with the issue of a black torso...
you want to composite the hair render on the body render... correct? so the hair render needs to have an alpha channel.
you don't want to set the body color to black and render, you want to hide the body and render the hair with an alpha pass in maya. you'll also want to hide the hair and render just the body in maya so you can composite the hair render (with alpha) on the body render in ae.
if you'll need to composite the body and hair onto something else in ae, then the body render should also include an alpha pass.
It's a tricky thing- if you render the hair with alpha, you get all the hair, the part that is behind the head as well, so comping that over the hairless character will not work. Instead of the black body/head, use a chroma green or blue shader with not reflection or shadows on (flat) - this way you can render that with the hair and alpha and then key out the color in AE to get only the hair that is visible on top of the head.