Oh ok that makes more sense to me, thanks. So basically the RT we're seeing in games so far is already so compromised at 30fps (quarter resolution) that they're hardly worth retaining at a lower resolution (because to get the standard benefit of halving resolution you'd also have to halve the RT resolution to 540p).
So in theory I was right - you should be able to do Watch Dogs at 1440p60 with RT - but the RT would then be so crappy it's not worth it.
Which is why we're seeing stuff like Spider-Man retain 4k to a large extent in 60fps mode, but jettison the RT.
Can't help but think that RT at this level just isn't worth the resources.
I wouldn't necessarily say that the RT reflections would look bad at quater resolution even at 1440p or 1080p, if they are properly filtered and maybe even implement some sort of checkerboarding, they could still look good at relatively low resolutions.
case in point, GranTurismo 7 on PS5. the demo they showed ran RT reflections at BELOW 1080p, so below quarter resolution of the 4K rasterized image. but they seemingly implemented a checkerboarding solution (that's what it looks like in early analysis) to up the perceived resolution of the reflections so they still look close to 1080p.
so in reality, these are 1/8 resolution RT reflections that look close to 1/4 resolution thanks to temporal upscaling.
I bet games will more and more optimize raytraced effects like this, especially reflections. proper filtering and temporal upscaling solutions will really help here.
and in some instances you don't even need that. if you look at a reflection on a flowing river, you rarely see a sharp image in real life either. so you also don't need a sharp reflection in the game. so reducing rays shot out for these specific elements also will help a lot.
another good solution would be to mix Screen Space Reflections with RT reflections, and to some extend that already happens (in Battlefield 5 some elements like bullet holes in walls only reflect in screenspace but not in the RT reflections) but this can be pushed and refined even more in the future.
maybe fusing Screen Space Reflection with Ray Traced Reflections seamlessly as you pan around the camera... everything on screen will be reflected using Screen Space, and everything off screen using Ray Tracing.
so there are ways in the future to optimize this and to make reflections look sharp even at a lower ray count.
