Second GPU to improve rendering preview speed?

[stephanbobby]

Hello,
i will buy a new workstation. My configuration is: CPU: AMD Threadripper 3960X, GPU: Nvidia GeForce 2080ti.

Now I wonder if a second GPU would make sense. I am not concerned with the speed of the final rendering, but with the speed of preview rendering / interactive rendering. So that you can see the result faster when adjusting materials and light.
Are two GPUs used for this and do you have a speed advantage?
Looking forward to experience reports!

[ThomasMiller]

As long as you're using V-Ray GPU, an additional graphics card should help with IPR (as far as I know -- I'm not a heavy GPU user). I do know for a fact though that GPUs will NOT help you with IPR if you're using V-Ray CPU. V-Ray CPU uses CPU for IPR, and V-Ray GPU uses GPU for IPR.

[Muhammed_Hamed]

Hey stephanbobby

A second GPU will double your final rendering/IPR speed when using Vray GPU
The IPR in Vray GPU scales linearly with as many GPUs as you add, I'm using 2x Titan cards.. it is crazy fast for look dev

[stephanbobby]

Thanks a lot!
Sorry, but what is IPR?

And: If I will use CUDA - Mode (CPU and GPU combined for rendering), will a second GPU also speed up the rendering?

[Muhammed_Hamed]

IPR is interactive progressive rendering, it is basically what you mean by preview/interactive rendering

And yes, a second GPU is gonna make your rendering much faster, it is linear scaling. 2 GPUs are gonna be twice as fast as one GPU
In this case you can use RTX mode(better than Cuda), because you have the new generation of Nvidia GPUs.. it is gonna be even faster

[stephanbobby]

OK, thats fine.
Now, if it makes sense to spend the money on GPU, does it make sense to spend money also on a fast CPU (e.g. Threadripper 3960)? Or will a slower CPU also be ok then?

[Muhammed_Hamed]

Many cheap CPUs could run 2 GPUs and even 3 or 4 GPUs

But this depends on what you will do Stephan,
Have you done any GPU rendering in the past? are you familiar with its limitations for the kind of work you do?

The 3960X is a great CPU, but a bit expensive. If you wanna balance out your build after you added the second GPU you can stick to Ryzen 9 3950X
it is only 25% slower than the 3960x, but it is much better value overall for what you pay. Here is a nice example build,

Aorus X570 master >> 350 Euros
Ryzen 9 3950X >> 700 Euros
Gskill TridentZ Neo 3600 CL16 4x16 >> 350 Euros
NZXT H710 >> 150 Euros
NZXT kraken X62 >> 150 Euros
Samsung 970 Evo 1TB >> 150 Euros
Seagate Barracuda 4 TB 7200 RPM >> 120 Euros
RTX 2080ti Asus Turbo x2 + NVlink >> 2x 1100 Euros
Corsair RMX 1000 Watts 80+ Gold >> 180 Euros

Going for 3960X + TRX40 board is gonna +1800 Euros alone
I hope this helps you out, if you have questions let me know.

[stephanbobby]

Have you done any GPU rendering in the past? are you familiar with its limitations for the kind of work you do?

Thats the point: I´m new with V-Ray. I´m not experienced with limitations of GPU-Rendering. My Laptop (Dell Precision M4700) is now 8 years old, and I will have to get a nowadays workstation. It does not support GPU-Rendering at all (Its a Quadro K2000M)

So: Maybe better to have a fast CPU (3960X) AND a fast GPU (2080ti), and maybe later a second GPU?

[Muhammed_Hamed]

Sounds good!
And If you like GPU rendering after testing it on your scenes, you can add one or 2 more cards later, whenever you want.

Even with one card like the 2080Ti your preview should be very fast, and you will get a good taste of how GPU rendering is like
You gonna need something like TRX40 Aorus Master for the 3960X, it is a great board.

This is quite a massive upgrade over your old laptop

[stephanbobby]

That wa a great help for me to make a decision! Thanks a lot!

[ThomasMiller]

stephanbobby , just out of curiosity, what kind of work will you be needing to render? Architecture, product, automotive... etc?

[stephanbobby]

Product design, esp. Furniture
www.stephanveit.com

[ThomasMiller]

Product design, esp. Furniture
www.stephanveit.com

Nice work. I think that for your use-case the GPU renderer would be advantageous. What do you think Muhammed_Hamed ?

[Muhammed_Hamed]

Agreed with Thomas!
He has the option to add more GPUs later, and even with one card + his CPU with Hybrid rendering it should be a great setup!

[Micha]

A second GPU is the best investment. You get 100% more speed. You never get so much speed increase like by the second card. For example if you bought a third card, you will get only 50% speed increase ... and at a higher count of cards you only get a few percent more speed. Also two cards can be used with NVlink and double the VRAM (but NVlinked GPU are a little bit slower)

But since you render product design only you could start with one GTX2080ti. The rendering should be quite fast. And one year later you buy a next generation of card, maybe a 3080ti with 16GB. Or means furniture design that you render interiors often? For interiors a second GPU is a good choice.

Also if you buy one 2080ti you could test how much speed you get. Maybe the IPR render speed isn't so much the problem and the workflow is slowed down by the scene update time only. This would be enhanced by a second card.