Thansk Ciro!
I found something out (via a reddit post) that I can put here incase somebody comes here. A lot of AOVs including the Shadow Matte ones do not work in GPU rendering! So a lot of my AOVs like the ones Ciro shows were coming out black. They work CPU only.
I had been working so long on this project I didn't even really think about this at all. Also the difference in CPU and GPU rendering is pretty high (for quality) on some stuff I'm doing, so I am doing a lot of GPU.
The AOV system has been pretty funky in Arnold in Max. There is no real way to check them in the buffer (unless you use ArnoldView which I largely gave up on due to so many issues with it and eventually having heavy scenes) And the names and titles are strange with no real pop-up info. Also a lot seem to be missing (at least as compared to V-Ray) and you have to hand-build or do some hoop jumping to get what you want.
Going from V-Ray to Arnold if I could change 2 main things I think it would be how excluding lights on objects or excluding shadows etc... works. I have loads of objects inside groups etc... and the modifier method is kinda strange so far. I havent quite adjusted to it. And the other would be the AOVs. It doesn't seem user friendly. I'm stumbling around including this very post finding out some work in GPU and some don't.
