Including UI layer to final output | Fish Eye Effect

[ChumbaWambalala]

Hi I'm trying to achieve a fisheye effect using the existing lens distortion post process effect with a wide camera fov. So far I achieved this result.

Everything works well but I want to remove this rippling effect on the outer part of the image similar to this real fisheye photo.

The easiest I can think of to mimic this result is to add a UI layer of a cookie cutout. So far it looks similar to the real one.

Unfortunately, this is not carried over to the final render of the perception camera. Looking forward to an answer.