progressive vs bucket GPU

[s_gru]

hi. quick question mostly for furthering my own understanding. in the user manual it says it's recommended for using bucket sampling for GPU render when 3 or more GPUs are used in one machine or if using Dist Rendering. i'm just wondering why that is?

i do notice that a scene i'm rendering (exterior) is taking about 2m to 2m10s per frame with bucket, vs. 1m05s to 1m15s with progressive. i have not previewed the bucket animation compared to the progressive animation, but the progressive with Dist Rendering on 8 cards looks fairly good. also note that i have not changed any other settings for rendering.

thanks,

[Muhammed_Hamed]

in the user manual it says it's recommended for using bucket sampling for GPU render when 3 or more GPUs are used in one machine or if using Dist Rendering. i'm just wondering why that is?

Hello!

Bucket rendering makes sure every GPU is utilized at 100% or near that, specially in case of multiple GPUs, you will see that each GPU is at 100% load most of the time. This is the nature of bucket rendering, where Vray assigns 6 buckets per GPU putting pressure on GPUs and keeping them busy
And for Distributed Rendering, Bucket mode uses less Network traffic overall and less system memory(Because the buckets gets written directly to disk, while in Progressive mode all data is kept in system memory until the rendering is finished)

This doesn't mean that one sampler type is better than the other, each one of these has its own uses and advantages. You also need to consider that Vray uses bucket/progressive rendering very efficiently, they are both quite fast and they make use of all Vray's smart sampling and scene adaptivity.
For me personally, I use progressive with animation rendering so I can set a a specific render time per frame say 1 minutes render time per frame or so.. And I will render one frame per GPU simultaneously, so in my case 4 frames per 4 GPUs in my machine
And for high resolution rendering, I use bucket mode with my 4 GPUs.. it does a great job!
Early on in look-dev I use progressive rendering to make test renders, I can stop the rendering after a minute or 2 when it looks clean enough .. instead of waiting for the buckets

i do notice that a scene i'm rendering (exterior) is taking about 2m to 2m10s per frame with bucket, vs. 1m05s to 1m15s with progressive

They produce different noise patterns, to compare them you need to make sure that the rendered image is as clean in both. Usually bucket mode will be cleaner(and slightly faster because Vray knows exactly the amount of samples within each bucket, compared to adding more and more samples progressively to the whole image)
And again, Vray uses its full potential on both modes, many people stick to bucket rendering exclusively as it supports resumable rendering and Cryptomatte(which is now supported in progressive as well)

but the progressive with Dist Rendering on 8 cards looks fairly good

Good to hear! Vray GPU scales linearly in both IPR and production rendering and gives you the choice between bucket/progressive modes.

[s_gru]

thanks that's great information! yeah and IPR which uses the progressive is awesome when some of our designers want to see what it's going to look like... it's like instant!

And I will render one frame per GPU simultaneously, so in my case 4 frames per 4 GPUs in my machine.

how do you do this?!

[Muhammed_Hamed]

how do you do this?!

Deadline, GPUs per task option I think or exporting mulitple bat files if you have experience with Vray standalone
There are quite a few tools that could do that, http://vrscenegui.de/
This workflow will have a big impact specially if you have a lot of textures, so instead of all GPUs waiting for the scene to load into VRAM.. each GPU will be busy with its own task

[s_gru]

wow i'll have to investigate that! that seems really cool.

[fixeighted]

Now that is interesting...thanks for the link to the GUI.
Although really this sort of utility is something that Vray should be shipping with, in my opinion, as I cannot be alone in finding standalone a little intimidating - so much so that I gave up
I was actually asking about its use in a separate thread but you are the only person who has offered this extremely useful info

[Muhammed_Hamed]

I'm glad this was helpful, I only got to see your post today.
I have talked to others who developed their own tools for Vrscene, personally I have been using this GUI for the past couple of years, it gets the job done. Deadline could do the same as well(it is what people use with other GPU renderers)

[fixeighted]

Yeah I just got Deadline working...in the hope (after the fact...project is done) that it could render a load of shots containing a ton of textures. Sadly and rather surprisingly it cannot do it. Backburner won that battle easily
Maybe this GUI would have helped so might give it a go and see what happens.

[Muhammed_Hamed]

Let me know how it goes