RTX or Cuda ? (my one GPU is a RTX 3090 and RTX mode is a lot slower)

[JezUK]

I’m new to RTX graphics cards, having upgraded my 1080 ti’s to an RTX 3090 (I will be adding a second one but for now I have only the one RTX installed).

I’ve also in the last couple of days, upgraded from Next to 5.0.

I did a couple of text renders in 3DS Max and am finding that GPU rendering, RTX 3090, is quite considerably slower in RTX mode than when using it in CUDA mode.

Please can you tell me is this to be expected and why/when would i choose RTX mode in V-Ray GPU ?

I have only an RTX card, but it seems pointless changing that setting to RTX mode, what gives?

(software versions as per my signature).

Thank you.

[nikolay.kusht]

Congrats on the new card! As for the RTX performance, it would be best if you could share some results and examples from your tests. It all comes to how heavy your scenes are(reflection, refraction, textures, lights, geometry). Have you done the same tests on different types of scenes that you have?

[piotrus3333]

interesting as I'm currently jumping onto VRayGPU. seems like a lot has happened in last 3 years.
JezUK are you running your displays from 3090 or keeping it only for rendering?

[JezUK]

Congrats on the new card! As for the RTX performance, it would be best if you could share some results and examples from your tests. It all comes to how heavy your scenes are(reflection, refraction, textures, lights, geometry). Have you done the same tests on different types of scenes that you have?

Hi Nikolay,

Thank you!

I will do so, but for now, I will say that my scenes being worked on were very simple interiors, using Override Material (so everything was clay) - the render times were something like 1m 5s (Next and 2021) versus 1m 17s (5.0 and 2021) - I was not expecting things to go in that direction

I will for sure do more tests and come back to you.

Many thanks.

[JezUK]

interesting as I'm currently jumping onto VRayGPU. seems like a lot has happened in last 3 years.
JezUK are you running your displays from 3090 or keeping it only for rendering?

I currently only have 1 x RTX 3090 Founders Edition, so I am running my displays from the 3090 as well.

[M.Max]

I know this is a basic question, but are you sure that you are not using your CPU for rendering too while you are using the CUDA engine? because that's enabled by default for Cuda and -currently- not possible for RTX.
that could be the reason behind the render time difference.

[JezUK]

I know this is a basic question, but are you sure that you are not using your CPU for rendering too while you are using the CUDA engine? because that's enabled by default for Cuda and -currently- not possible for RTX.
that could be the reason behind the render time difference.

No, it's not that, CPU is not checked, if I had CPU checked for CUDA, my machine would render even slower.

Just performed a decent sized render - CUDA 9m35s, RTX 10m27s.