In this YouTube video, the creator mentions that reflections in Unreal Engine 5's Lumen "work by tracing the path of light as it bounces off of surfaces in the game world." Does this mean that Lumen uses raytracing? I thought that this was difficult to do in real time on consumer hardware. But more importantly, how can I implement the same technique? Can I do that with OpenGL or Vulkan? How much of the existing rendering pipeline do I in that case need to re-implement myself, and how much of it can I reuse?
Side note: I don't only plan to use it for reflections, but also for transparent objects that bend light in various ways (for which rendering to a texture doesn't work because there is not a single point from which to do that rendering), but I—perhaps somewhat naively—assume that reflections and refractions can both be implemented using the same or very similar techniques.