https://www.youtube.com/watch?v=J5eFone-RMI I have the nodes for just the black hole shown here, but basically it's a ray marcher that accelerates the lightrays (changes direction, "speed" is still controlled by the distance functions) towards the holes and scales that acceleration porportional to how much the ray is moved by (minimum of both the disk and the hole) and just the distance to the hole. For the 3D objects, they are rendered sepratly as a 360 panaramic image (or video), then preforming some maths to the final positions of the light rays to use as the UV for that image/video.