Hardware Ray Tracing Confusion

Hey, first of all i have an rtx 3070. here is one thing i am having a hard time understanding, with the default settings on the Ancient example i get around 60 frames when Lumen is turned on and the hardware ray tracing is off. Whenever i turn hardware ray tracing the fps drops to 10ish, even though i have “use hardware ray tracing when available” option turned off, so basically i am not running ray hardware rt, basically just software lumen like on previous settings but my fps drops 6 fold even though everythings exact same like before, dont really get whats going on here. Use hardware ray tracing when available option doesnt actually make a real difference i can tell, maybe 1-2 frames, but the quality is real different.

Another thing i realized was some architecture project i was working in the office was giving me good enough fps(40 something) with hardware rt, then as soon as adding some quixel materials it dropped to like 5-6 which made me think it was an issue with the materials of course, turning hardware ray tracing back off lets it jump to 40s again.

One more thing is that i expect getting some extra boost from my 3070 to give me better results than software ray tracing but it doesnt, so whats actually is the point here of having lumen on hardware mode when i get really similar performance as brute force? I know that 3070 is not the best rt card out there, but its definitely above average. I would appreciate if anyone could help me to understand what exactly is going on, a couple hours research didnt get me any results so thanks

I understand your confusion, but there are some key points of interest when changing settings that you should be aware of:

  • Real-time Ray Tracing by hardware on NVidia cards with low amount of VRAM needs DLSS, which basically will render in lower resolution and scale up. You could say about the same on AMD cards.
  • If you have Ray traced GI (Global Illumination) turned on and it is using RT by hardware it will take a huge cost for open environments, but will be ok for closed environments.
  • Size of the textures you are using might be too high, which will require large amount I/O to load the textures which will reduce the overall frame rates, and those sizes will cost more on HW RT if you are not using DLSS.

I recommend to make sure when you are enabling Lumen with HW RT, that Global Illumination is not enable with HW RT, let Lumen handle the GI.

It would be interesting if you could share more about the scene in question to allow the forum audience to give you more hints on whats going on. :wink:

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