Invisible object with an alpha

Support Compositing and Post Processing
1

Hello,

I’m wondering how to set my material so that an object is invisible, but still has an alpha channel that knocks out objects behind it. Basically, I need to object to exist in the Alpha Channel only and not in RG&B Channels.

Any help is much appreciated.

Thanks

2

In the “Options” section of your objects’s materials, check the “Sky” box. Should do what you need it to. (This is for 2.5X)

3

Hmmm…

That seems to knock out things in front of the object as well. Essentially I’m trying to make smoke look like it’s coming out of a doorway and around the doorway. I want collision objects to disturb the smoke, but I don’t want to render those collisions objects because they represent the doorway that was filmed in the backplate.

Hope this is making sense.