RTX speed increase?

[francomanko]

So does anyone have a scene where they have seen a noticeable speed increase using rtx over cuda? Before getting my 2080ti i was reading that you could expect upto 30% increase and I know its scene specific but i would have thought i would see some increase.



For that cuda was 1m27 RTX 1m25

[Joelaff]

On my workstation with a thredripper and one 2080Ti RTX is SLOWER than CUDA because RTX mode can't do hybrid, so the CPU's multiple threads sit idle.

So if you have a fast CPU the increase may negligible or negative.

[glorybound]

Yep, hybrid is slower for me.

[francomanko]

thanks for response. Im not using hybrid though, just the gpu.

[glorybound]

For me, RTX and CPU are about the same in speed for exteriors, Interiors, RTX is faster, however, start and stop is slow and it crashes often, and it crashes so hard I have to reboot MAX to use it again.

[Joelaff]

thanks for response. Im not using hybrid though, just the gpu.

Hybrid only works with CUDA. But why would you NOT use Hybrid with CUDA? It's free extra power (the CPU). (Well, it uses more electricity; so not free.)

[seandunderdale]

Id be interested to know where RTX make most of its gains. Is it scenes with lots of geo? lots of textures? lots of lights? I almost exclusively render high res CAD car assets, so Id love to know where RTX is most efficient. If its arch vis interiors, then maybe I should stick with a fast CPU.

[oglu]

If there is a lot of geo in the scene with less complex shaders RTX will be fast.

https://www.chaosgroup.com/blog/what...endering-v-ray

[francomanko]

Hybrid only works with CUDA. But why would you NOT use Hybrid with CUDA? It's free extra power (the CPU). (Well, it uses more electricity; so not free.)

because its slower.

[Karol.Osinski]

Hybrid only works with CUDA. But why would you NOT use Hybrid with CUDA? It's free extra power (the CPU). (Well, it uses more electricity; so not free.)

I've heard that in some cases lower end CPU can cause slow downs as it is very difficult to simulate CUDA cores on CPU - someone please correct me if I explained it wrong.

seandunderdale I think GPU struggles the most with materials while being fast with lots of geometry. I remember from some webinar about Project Lavina that Chaos Group guys are trying to balance out the sampling between lights, geo and materials.

[seandunderdale]

That'd make some sense as the studio Im working for are fully into GPU - RTX rendering for heavy cars (lots of geo), but they don't like us using complex shaders with blend setups or too many complex texture trees. They like to keep render times super super low....Im talking under 5 mins for a 4k car. Ive found some serious slow downs on GPU using stochastic flakes, but more simple stuff, with denoiser, it can be really quick.

[Joelaff]

because its slower.

What exactly is slower? CUDA Hybrid vs. RTX?

Or CUDA Hrybrid vs. CUDA without the CPU?

On my system CUDA hybrid is faster than CUDA non-hybrid and faster than RTX (which is always non-hybrid).

[francomanko]

Last time i checked, hybrid was slower than everything else....but to be honest hybrid mode isnt the original question, dont make me do another test pleassee

[Morbid Angel]

I'm not sure how some one can use gpu in production anyway. The limitations and instability quickly outweight any speed gains *(which are marginal) over cpu.

[francomanko]

well it says on the box that it does gpu rendering, so that should be enough..come join me on the gpu rollercoaster

My project was a smallish residential one, so I didnt think i would have so many issues, scenes are no where near pushing the limits.