Background + shadow_matte

[Anonymous]

I built this simple scene to show my problem. I want to render this glossy sphere with a background image and a shadow matte. I render to the output_exr.

In photoshop it looks like this. How can i render this with transparency at the area of the background??
I don't use the RGBA but the other 4 channels so its black.

When i switch off the background for rendering its of course transparent but also missing in the reflection in the sphere.

I would be very happy to get a solution for this or maybe i do something wrong?
I just render stills and compose 3d on the background in PS later.

Arnold v2.4.2
C4d R20.026

[peter.horvath6V6K3 · Accepted solution]

If I understand correctly what you need is to get rid of the alpha of the background, right? That's the alpha channel of the image, so you can for instance add a color_correct shader and multiply the alpha by 0.

[justin_rogers1]

anyone know how to render an animated background texture (mov)?

[peter.horvath6V6K3]

Arnold does not support video files as textures. If you convert your mov to a sequence of images then you should be able to render it as animated background.