UE4 Stencil Layers - compatible with V-Ray?

[story_garvie]

I'm still new to this, and I'd like to be able to render certain assets on an alpha channel. It looks like I can do a UE4 render this way by using Stencil Layers, and I've done it successfully, but I'd like to know if V-Ray supports this, and where I would find the settings for it.
Example: I have a coffee table in a room, with a vase on it. I'd like to be able to render the entire room, but with the vase on a separate layer with alpha channel. So I'd end up with the main render WITHOUT the vase on the table, and a separate render of just the vase on an alpha channel, but still capturing the reflections of the room around it. I need to do this for both stills and animations.

[Alexander.Atanasov]

Hi story_garvie,

UE Stencil layers are not currently supported in V-Ray for Unreal. You could try to use the Cryptomatte render element where a mask for each object in the scene (when Id type is set to Node name) will be generated which later you can use in Nuke/After Effects. Unfortunately I cannot think of a way to have the render of the only the vase but with reflections of the room without it being visible. The only way I can think of is having 2 renders - one with the vase on the table and one without. Can you explain more what is the end goal/product?

Best regards,
Alexander

[story_garvie]

An illustrator will be adding drawn figures standing behind a railing on a refinery tower. I'd like to render the refinery scene without the railing (the space where the railing is could be on alpha channel or not, doesn't matter), and with ONLY the railing on alpha. This would need to be for both stills and animations.

[Alexander.Atanasov]

Well, the cryptomatte render element should do the trick. You can use it to mask that railing on a copy of the original render/sequence and insert the illustrations you want in between. What software would you use to do the compositing so I can try it on my end?

Best regards,
Alexander