Some clarifications:
- The 1/2 resolution for ac shadows is for ray traced specular as RTGI has 2 components - Diffuse and Specular. Slide 1 is for diffuse at quarter resolution I.e 1/4 rays per pixel and slide 2 is for specular at half resolution or 1/2 rays per pixel. The simplified role of diffuse is to cover GI for light scattering on rough surfaces, which results in indirect lighting, color bounce etc. and specular does that for shiny surfaces where light scatters less and is more mirror like.
- Due to the nature of rough vs shiny surfaces, you can get away with fewer rays per pixel for diffuse. Specular needs to as close to 1:1 as feasible because noise from specular is far more noticeable due to its brightness.
- So for ac shadows, they went with 1/4 diffuse and 1/2 specular as they saw big gains in choosing 1/2 over 1/4 for the specular portion of RTGI. The diffuse stayed at 1/4. Not 1/2, which is the error I see in your interpretation.
- For comparison, crimson desert does 1/16 for diffuse and 1/4 for specular. So the apples to apples comparison would be - 1/16 vs 1/4 for diffuse and 1/4 vs 1/2 for specular
- Another point of reference is GoY. They use a dynamic range where they scale rays per pixel to the dynamic resolution based on load. In the worst case scenario, they use 1/10 rays per pixel and scale all the way up to 1/4 rays per pixel for diffuse. I think they don't use RT for specular and rely on baked lighting for that.
And RTGI in GoY is already pretty subtle with 1/10 as the rock bottom worst case. At 1/16 all the time, you have very, very little to work with and using a non-AI denoiser is just going to wipe out most details as the sampling is too low. You would still get the big details, like overall lighting of a room, but none of those details around objects. So your conclusion is still right. Just wanted to clear up what the numbers meant.
Without AI denoising, it's closer to probe based RTGI like Indiana jones on console than AC shadows, which is doing 4x more rays for diffuse and 2x more for specular.
It's AI/ML based, so it's not a feasible solution on base consoles. And it hasn't been ported to the Pro. Not yet at least. This is literally the second game out with AMD's RR and it has been around just a few months