Pathtracing-GI @ low (better quality than anything in UE5) in Alan Wake 2 has a 20% hit on Lovelace. And the GPU is still under full load, so there are no bubbles and non processing bottlenecks.
Why should there be any? "flexibility" is the problem here. DXR is good enough for real time Pathtracing. Raytracing is a compute heavy workload. So making it more flexible will always cost performance.
But here is the fun fact: Even with 100 TFLOPs Epic cant use a modern GPU to its full potential with their software solution. So i guess we do not need more functions but just a different kind of fixed function units.
Here is another fun fact: UE5 runs on Maxwell. Blaming an API from 2018 for an engine for 2014 hardware is strange to me.
Despite DXR may be not progess much nVidia has. Providing not only much faster RT hardware (4x triangle intersection tests per RT Core, 6x including higher clock rates since Turing) but releasing new API functions for their hardware: SER and OMM. And yet none of these advanced has been implemented into the main UE5 branch. So no, DXR as an API is not a problem.
And none UE5 games support it. Robocop would have been a prime example for better reflections.
Missing proper HW RT implemention is only one of the problems. Another one is the slow performance on nVidia GPUs. Jusant runs with only 60 FPS in 4K on a 4090. Metro Exodus EE with a better and more compute heavy GI implementation gets over 100 FPS. AMD GPUs do not lose much performance going from Metro to Justant. It is nVidia who gets crippled by an unoptimized application.
