Catching Light With Transparency

[Anonymous]

Hi, I know that you can use the aiShadowMatte shader in arnold to catch shadows with a transparent background but is there a way to do this with light instead of shadows? I have a mesh light that is illuminating a plane behind it similar to how a neon sign would illuminate the wall behind it. I would like to export this so that it keeps the lighting information from the mesh light but the plane itself is transparent. The goal is to have this overlayed over an image.

Thank you for any help you can give me!

[ecic2002]

I think what you are looking for is an aiAtmosphere. In your Arnold render setting, scroll down to environment. Click the checkered icon near "Atmosphere" and select aiAtmosphereicVolume. Set the density to 1. This will render the glow of the light creating a similar effect to what you described.

[Anonymous · Accepted solution]

That's an interesting way to go about it, I didn't think of that. Although I found that I could get the result I wanted using AOVs.

Thank you for the response!

[george.stamenov]

Can you explain how did you get it to work? I am looking to get a couple of lights with alpha.