Not sure if this is possible, but I was wondering if you can use an alpha value from a material as a holdout option for compositing?
The thing is that I have a scene with objects that I want to fade out, but I don’t want the background to appear where those objects are fading out.
Is this possible? Otherwise I see my self rendering the objects separately to them start layering them in compositing.
Any help or ideas would be appreciated.
Thanks.
What do you want to appear while the objects are fading? If the background isn’t showing through them but they’re transparent, something has to be showing though, so what is that?
It wil be the same scene but with different materials. Basically I have 2 scenes the same. One with animated materials where I have created a nice procedural dissolving effect for the fading out. And then I have the exact same scene with different material as normal environment would be.
So I want to make some objects and walls, etc to dissolve and fade out to convert to the normal (no effects) scene.
Not sure if that makes sense?
Why about… render the other scene as a still image and put it behind the dissolving material? You can do this with compositing or however you want, this way would be a lot faster though 
It’s an animation. I mean both scenes (which are the same apart from the effects) are animated
Sorry, I should have specified better XD
I found the solution. There is a holdout shader that I can replace with the transparency shader. Never knew about this, but it does exactly what I want XD
Thanks anyway for the help!