Long time Lurker, second time poster. A while back i wrote a GLSL shader to emulate the look of a camera lens. Its a single pass shader that uses multiple layers of depth to create the illusion of a deep stack of lenses. I distort, scale, and shade each layer depending on view angle. Its all a big cheat since its all hard coded and does not contain any fancy ray-casting code. I use it for real-time rendered logotype of Ministry of flat, a UV unwrapping tool Ive been working on, but the plan is to use it for other logos, so it has 4 color parameters so that i can make multiple versions of it.
I would like to keep exploring this kind of more artistic take on Parallax mapping. I would love to make some kind of paintbrush art style where multiple layers are separated by depth.