*This is where I am kinda mad at Nvidia, because they turned an algorithm into a brand.
So, the emissive material thing is strictly about how you’re able to sample a scene around you. Most lights in games are punctual, meaning they’re not made out of geometry, but out of equations that create shapes like cones and points and planes. The engine knows where they are at all times, so it’s super easy to send rays their way to trace. Emissive materials take more processing power to solve correctly because the engine has to guess at where they are in space to light them (rather than just knowing beforehand with punctual lights). Lumen can do the exact same thing.
Megalights can handle 1000s of moving lights too. Attenuation radius is too complicated a subject to get into.
I can guarantee it produces noise. It’s impossible for it to not produce noise, because the core of the algorithm is just taking a guess at lighting; when that guess is wrong, it’s noise.
Anyways, ‘realtime path tracing’ as Nvidia brands it performs definitively worse than lumen. It’s simpler algorithmically, and it can scale up to higher quality, but it can’t run better in like-for-like scenarios, or at least I would be truly stunned if it did.