I am on the composting phase of an animation and there is an effect that I want to add. Which can be seen at this link https://youtu.be/n8-AywU_2_w?t=42s.

If you take a look at the floor you will see a slight reflection.

In my scene I have made a separate render layer, applied a mib glossy reflection to the floor plane and I am getting the reflections just fine. However I can't figure out how I can render it out in such a way that it will be reflections only with an alpha , kind of like how use background and mip matte shadow shaders work with catching shadow. As it is right now the floor renders out black with the reflections. The problem is that when I bring it into after effects "screen" and "add" operations don't work with black. :/

I mean I could render out the whole scene, but that would be too costly, I figured this would be a simple add on but it is proving to be otherwise.

Working with Maya 2013.

Thank you for your time.