background

You can drag a material location to this parameter, which material defines the shader to be run when rays hit the background.

Note that it is preferred instead to use a skydome_light instead to generate a background, and there is an additional shader slot for background rays there.

background_visibilty

Note that KtoA defaults to a background that is invisible to camera rays, as that is the typical workflow for images with compositing as their destination.

atmosphere

You can drag a material location to this parameter, which material defines the shader to be run when rays evaluate the atmosphere volumetrics.

skip_background_atmosphere

low_light_threshold