How do I add a global post processing shader which projects the scene texture onto an arbitrary mesh instead of a screen-aligned quad/rect?

Sorry, I sould’ve explained myself better. What I want is a post processing effect that, every frame, takes the image the camera has rendered as an input texture, applies it to a mesh, renders that mesh and outputs the resulting image to the screen.

That should give me a way to deform the rendered image based on the shape of the mesh: By setting a cylinder or a sphere as the mesh I could make it seem like the game runs on a curved monitor even on a flat screen.
Unfortunately for me, I lack the experience in graphics programming to find a solution on my own.

From what I’ve seen so far I believe that creating a material that does this is either impossible or needlessly inefficient, but global (HLSL) shaders look far more promising. There’s a good up-to-date guide on adding some simple global pixel shaders on Caius’ blog, but setting up global non-pixel shaders (e.g. vertex or geometry shaders) seems incredibly complicated by comparison and I have yet to find any up-to-date information about them online, hence why I’m asking here in the Unreal forum.

And thank you for taking interest ^^