Unable to use the background render element or alpha

Hi,

I wanted to render the scene attached to this post with the background masked out.
I made sure to switch on invisible in the dome light and I had no background for this scene. (my sunlight and environment were turned off)

But it simply rendered the background as black.

And the alpha was simply showing white. I also made sure to save it as a png.

What’s the best way to mask out the background and later use it in photoshop if we’re using a domelight to light our scene?
I couldn’t find an option to add a material ID to the dome light background.
And the alpha and background were simply rendering out as pure black and black.



Hi,
you have to go to your window glass material options and than into refraction → affect channels → color+alpha.

Thanks a lot