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Comment by valine | Hacker News Reader

The thing about path tracing that isn’t mentioned often is that it can take anywhere from 1/60th of second to 16 hours to render a single frame. The images that people associate with path tracers are usually of the 16 hour variety. Just because a game could technically use a path tracer as it’s render engine doesn’t mean it will provide any visual benefit over traditional realtime rendering.

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This is of course true, to the extent that it can take a long time for a path-traced image to converge to a low level of noise. But there are significant advances in using advanced filtering techniques (e.g. temporal filters) that are already very good at filtering out noise in images moving at or near interactive framerates. In combination with the kinds of effects you can capture with path tracing, definitely will provide visual benefit over rasterization.

That said, I'm not convinced that path tracing and physically-based rendering methods will ever completely replace rasterization. For some applications (especially games), the kinds of non-realistic effects you want to achieve are actually very hard to model and render using techniques that aim for realism. Probably for games we will end up with hybrid rendering that uses both at the same time.

Two points:

- What you said is true of any rendering method you use. If you have a complex scene, it'll take more time to render one frame.

- What I said about 2018 or 2019 is what nVidia's promotion is all about. See the demos linked at the bottom of my comment. They keep calling it 'real-time ray tracing' but it's really 'real-time path tracing'. And it's already happening.

[1] https://www.youtube.com/watch?v=Vdnwrt3Xdak

[2] https://www.youtube.com/watch?v=tjf-1BxpR9c

[3] https://www.youtube.com/watch?v=jkhBlmKtEAk

I don’t think that’s realtime path tracing. It looks to me like they’re doing ray traced reflections and shadows and combining that with light probe global illumination. It’s cool, but not revolutionary.

These samples just don’t look that impressive to me. It looks like they are just milking some tweaks in each one.

[1] Looks really good but only one light source and barely even a bounce of light. Nice backlight halo, but that’s not ray-tracing.

[2] Obviously a lot going on here and some progress of some sort but if only all the reflections weren’t so blurry. What’s up with that?

[3] 99% of what makes this scene look good is the PBR texture tuning. This lighting does not look good and nothing is moving. Very few reflections and small but they do look proper.

[2] At 3:43 and 5:12 you can see the reflections at different levels of roughness. The rougher the surface, the more diffuse it will appear.

[1] - in 2:19 as well? It looks like there are bounces and multiple sources...

Good to see that they are following the universal law of raytracing demos: a reflective sphere stuck randomly into the scene (at just under two minutes into the first video)

If you're trying to demonstrate the 'real world usefulness' of raytracing in games, the appearance of shiny ball bearings is a clear sign that you've run out of ideas.

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