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Comment by mattnewport | Hacker News Reader

Depends what you mean by 'needs'. The combination of dedicated ray tracing acceleration hardware and APIs to drive it with some remarkable advances in denoising, in part driven by deep learning plus associated dedicated hardware, means that we are at a threshold where hybrid techniques that mix rasterization with ray tracing are viable for games and can advance the state of the art in real time rendered image quality.

That certainly doesn't mean real time rendering is 'solved'. We could certainly use another 3 orders of magnitude compute performance (and more) if we had it to get better visuals. That's pretty much always been true for graphics though.

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Yes, I'm only talking about "non-hybrid" GI - I.e. what is needed to play a game looking the same in terms of detail, sharpness etc. as a rasterized game does today, at 4k/60 or 2k/144, but using path tracing.

Hybrid (shadows, reflections only) already works today and looks pretty impressive. But just a rough guestimate of how many more rays/pixel we need to play a AAA game with PT only? I'm thinking 1000 times.

I don't think your estimations take into account the massive gains from AI denoising techniques such as https://youtu.be/YjjTPV2pXY0

Yes, well I tried to extrapolate from the demos we see now, using AI denoising. It certainly does look promising, and even if there are artifacts e.g. at rapid movement, one could easily imagine just dropping to a simpler rasterizer when moving rapidly (to avoid dragging) and then refine.

I think we'll get there with less than a 1000x increase in raw compute due to a combination of factors.

For one, ray tracing in hardware is new. We've had many years of clever techniques to improve efficiency of rasterization in hardware so overall performance has improved faster than raw compute. I think we can expect similar improvements for ray tracing.

We're also likely to see new algorithmic advances that let us get better results with fewer rays. There was a whole course at SIGGRAPH on applying machine learning to light transport problems, things like learning probability distributions for irradiance to do more effective importance sampling with promising results. Combined with the advances in denoising there's a lot of potential for improved results without more rays there. Lots of scope to take more advantage of temporal coherence I think too.

On the hardware side there is still room to scale wider for ray tracing. It's getting hard to make transistors smaller or faster bit there's still some room for putting more of them on a chip it seems.

Combine all these and I think we're a lot closer than a 1000x increase in raw compute to real time path traced games. Primary rays might still be rasterized though, it still has coherence advantages.

> But just a rough guestimate of how many more rays/pixel we need to play a AAA game with PT only? I'm thinking 1000 times.

Depends on the LOD and number of lights you want. You can get a better image than raster using only one or two shadow/reflection bounces and several lights. At 10 Giga rays, the 2080TI could do 166,666,666 rays per frame at 60fps. 4k screens have 8,294,400 pixels, so for every pixel you could have one initial ray with at maximum 19 shadow rays. Of course when you introduce a few reflection bounces etc. it becomes significantly less rays/pixel.

This would absolutely max out the RT cores to their theoretical limit, so I imagine we will stick with hybrid for a while but I think 1000x is an extreme estimate.

(Unless of course my math is wrong here.)

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