Comment by bob1029
3 days ago
It will never be fast enough to work in real time without compromising some aspect of the player's experience.
Ray tracing is solving the light transport problem in the hardest way possible. Each additional bounce adds exponentially more computational complexity. The control flows are also very branchy when you start getting into the wild indirect lighting scenarios. GPUs prefer straight SIMD flows, not wild, hierarchical rabbit hole exploration. Disney still uses CPU based render farms. There's no way you are reasonably emulating that experience in <16ms.
The closest thing we have to functional ray tracing for gaming is light mapping. This is effectively just ray tracing done ahead of time, but the advantage is you can bake for hours to get insanely accurate light maps and then push 200+ fps on moderate hardware. It's almost like you are cheating the universe when this is done well.
The human brain has a built in TAA solution that excels as frame latencies drop into single digit milliseconds.
The problem is the demand for dynamic content in AAA games. Large exterior and interior worlds with dynamic lights, day and night cycle, glass and translucent objects, mirrors, water, fog and smoke. Everything should be interactable and destructable. And everything should be easy to setup by artists.
I would say, the closest we can get are workarounds like radiance cascades. But everything else than raytracing is just an ugly workaround which falls apart in dynamic scenarios. And don't forget that baking times and storing those results, leading to massive game sizes, are a huge negative.
Funnily enough raytracing is also just an approximation to the real world, but at least artists and devs can expect it to work everywhere without hacks (in theory).
Manually placed lights and baking not only takes time away from iteration but also takes a lot of disk space for the shadow maps. RT makes development faster for the artists, I think DF even mentioned that doing Doom Eternal without RT would take so much disk space it wouldn’t be possible to ship it.
edit: not Doom Etenral, it’s Doom The Dark Ages, the latest one.
The quoted number was in the range of 70-100 GB if I recall correctly, which is not that significant for modern game sizes. I’m sure a lot of people would opt to use it as an option as a trade off for having 2-3x higher framerate. I don’t think anyone realistically complains about video game lighting looking too “gamey” when in a middle of an intense combat sequence. Why optimize a Doom game of all things for standing still and side by side comparisons? I’m guessing NVidia paid good money for making RT tech mandatory. And as for shortened development cycle, perhaps it’s cynical, but I find it difficult to sympathize when the resulting product is still sold for €80
Devs get paid either way, consumers just pay for more dev waiting instead of more game.
You still have to manually place lights. Where do you think the rays come from (or rather, go to).
It's fast enough today. Metro Exodus, an RT-only game runs just fine at around 60 fps for me on a 3060 Ti. Looks gorgeous.
Light mapping is a cute trick and the reason why Mirror's Edge still looks so good after all these years, but it requires doing away with dynamic lighting, which is a non-starter for most games.
I want my true-to-life dynamic lighting in games thank you very much.
> it requires doing away with dynamic lighting
Most modern engines support (and encourage) use of a mixed lighting mode. You can have the best of both worlds. One directional RT light probably isn't going to ruin the pudding if the rest of the lights are baked.
How is Metro Exodus Enhanced Edition (that is purely raytraced) compromised compared to regular version that uses traditional lighting?
> It will never be fast enough to work in real time ...
640Kb surely is enough!