Studio Rendering but Exporting background Elements as Alpha

[jujubee]

It's been a very long time but I can't seem to get this to work. I know it's probably been asked a million times but I couldn't find the answer.

I have a model inside of a "studio" setup.
I want to be able to render the model, but assign all of the background elements as an Alpha, so I can simply save the image out as a .png with a built-in alpha channel and no extra post processing steps.

I need the studio background and box in order to bounce GI and reflections around, but I also need it to not be transparent too.
If this was a single image, many years ago with VRay I would have assigned it IDs and just rendered out a separate ID channel.
But since there are tens of thousands of these images, to manually have to combine each one would take too long.

I'm moving back from Octane where I had the setup so that the background setup contributed to the model but was never rendered out. It was as simple as saving out to a .png.
Is there an easy way for VRay to do the same?

[fixeighted]

All that you should need to do is to select all of the backdrop models and then look for the icon on the Vray toolbar that makes them all matte objects...it's a blue sphere with a dotted red box.
You can check in Vray properties to see what that button does (in the Matte Properties at top right).
You can further use a Material Wrapper which has some other functionality...just look that up in the docs is easiest

[jujubee]

Okay Thank you I feel stupid for something so simple but I appreciate you answering that.
I never thought to make it a -1.0 value as I thought simply checking matte before as it defaults to 0.
It appears that this AND then setting vray properties with "Matte for refl/refr" needs to be unchecked is what I was looking for (in case this helps someone else.)

Thanks Again.

[fixeighted]

No problem. Live=learn