- Jan 18, 2016
Actually RTX performance in ray-tracing very good.From what I can gather, DXR requires support for the DX12_1 feature set called Conservative Rasterization. Pascal has support for Tier 2; Turing, Vega, and Volta has support for Tier 3. This allowed nVidia to create a driver for the Pascal, Turing, and Volta architectures that can handle DXR. nVidia cards with RTX can hardware accelerate the DXR operations allowing for better (note I did not say stellar) performance. Presumably AMD could use the Tier 3 feature set in Vega to enable DXR support; non-hardware accelerated, of course, just like my 1070 so naturally the performance is piss-poor.
With each ray intersection is handled by not-so-simple shader program and given DXR effects are mostly added on top of existing effects which already stress shaders a lot (or replace much cheaper shader based effects) it is no wonder performance with DXR enabled is worse than with it disabled. This will never change!
Some of these shaders which are executed with each ray intersection could be made into fixed hardware and with this approach performance would be much better but that would allow far less flexibity and would require even more silicon. DXR is designed to be fully programmable so any effect can be done with it from simple reflections to more elaborate path-tracing implementations and even things which one could hardly call ray-tracing like using RT cores to calculate realistic sound effects, etc.
Of course I would not expect first HW implementation to be most optimal and some tweaks can surely be made to make RT better. More optimizations can be however expected from game developers than from Nvidia or anyone else.