keyer screen inside a roto mesh

hello everyone
I’m trying to figure out where I’m wrong but I don’t see errors:
I’m trying to remove the green screen from two images and combine the subjects on a new background, but what happens is this, any advice?
this is my project:

with keyer in screen mode i removed the green screen but when i select a mesh with roto, a black background appear around the mesh…
Thank you

can anybody help me?

Can you share the project and files?


Files: (46.3 KB)

ok so it took me some time to figure out what was wrong. Turns out the Keyer node doesnt work well in this scenario so you have to use the ChromaKeyer node as in my file and screenshot.

The Roto node is used as a ‘garbage matte’ for the ChromaKeyer. A ‘garbage matte’ is a mask used to “remove” parts of an image from a process. In short, it tells the software which parts of the image we want and dont want. In our case, we want to key Read2 but we dont want the blue circle, only the magenta box. So we add a garbage matte to the magenta box and set it so that everything outside the mask is grabage, i.e. we dont want it.


So after the ChromaKeyer, what we get is:


Now when you try to merge the output with something else, it works:


(the Premult serves no other purpose than to fix edges after the key… Better edge refining can be done before the Premult)