min shade rate

[yones]

hi. when we use gpu rendering, where is Min Shade Rate parameter?

[Muhammed_Hamed]

This option doesn't work on GPU, and you shouldn't touch it for the CPU engine
It will be removed in the future from what I have heard
But for the GPU engine, it is smart enough to learn about the scene and decide the right balance..

Default min/max 1/100 subdiv and noise threshold of .01 is more than enough for most scenes on GPU
And if you are using bucket mode, use max subdivs of 48, and like .02 for noise threshold.. it should be enough for most scenes
If you need cleaner renders, you just go down on noise threshold to .008 or .005

[Micha]

Muhammed_Hamed Interesting, why do you use a rawer noise and less max subdivs for bucket mode? I used 1/100 and 0.01 for both modes. Sounds your bucket mode setup could be faster, but will it not produce more noise than the progressive mode?

[Muhammed_Hamed]

Muhammed_Hamedwhy do you use a rawer noise and less max subdivs for bucket mode? I used 1/100 and 0.01 for both modes. Sounds your bucket mode setup could be faster, but will it not produce more noise than the progressive mode?

Specially on GPU, bucket sampler is very sensitive and cleans up the image extremely well
Noise threshold of .02 with bucket mode on GPU will give you clean renders in most cases, you will need .01 noise threshold with progressive mode to achieve the same clean result
About Max subidvs, I use 48 with bucket mode, it is more than enough for 99% of cases(unless you have bokeh noise for example)
You should consider that bucket/progressive will give you different noise patterns.. bucket mode will always give you cleaner renders, it is just how it works(Vray knows the right amount of samples to use within each bucket, on the other hand with Progressive Vray adds more samples in each pass) And there are cases where bucket mode is faster than progressive..

It is a different story on CPU, I usually use .005 noise threshold with bucket mode, it doesn't clean the image as well as what the GPU engine could do

[Muhammed_Hamed]

So to answer your question Micha, "will it not produce more noise than the progressive mode?"
Nope, Even with lower max subdivs, bucket mode will give you cleaner renders and faster of course
you don't need 100 max subdivs with bucket mode, 48 is more than enough (for most cases)
And .02 noise threshold is quite good in most cases as well
With progressive mode you need 100 max subdivs and .01 noise threshold

[Micha]

Great, so my renders will be faster again. Great times. Thank you for the suggestions.

[AbeTJH]

Specially on GPU, bucket sampler is very sensitive and cleans up the image extremely well
Noise threshold of .02 with bucket mode on GPU will give you clean renders in most cases, you will need .01 noise threshold with progressive mode to achieve the same clean result
About Max subidvs, I use 48 with bucket mode, it is more than enough for 99% of cases(unless you have bokeh noise for example)
You should consider that bucket/progressive will give you different noise patterns.. bucket mode will always give you cleaner renders, it is just how it works(Vray knows the right amount of samples to use within each bucket, on the other hand with Progressive Vray adds more samples in each pass) And there are cases where bucket mode is faster than progressive..

It is a different story on CPU, I usually use .005 noise threshold with bucket mode, it doesn't clean the image as well as what the GPU engine could do

Where is the Min and Max subdivs in the VRay GPU render settings? I can't seem to find it. Its in the Vray tab for cpu.

[Muhammed_Hamed]

Well, I cannot find these in Max UI
But it is what I use in Maya/Modo and Houdini.. Micha uses Rhino which has min/max subdivs in the GPU UI too
I'm not sure how you would access these in Max, sorry

^Lele^ a7az0th should know.

[Micha]

At Rhino we have min/max for the bucket mode only, progressive only the threshold.

[a7az0th]

In Max subdivs are not present in the UI on purpose. All you need to do to in Max is tweak the V-Ray->Render settings -> Samples limit parameter.
This tells V-Ray GPU how many samples it is allowed to shoot (it can stop before reaching this value, if the Noise threshold falls below the value you have specified)
Based on this value it will determine the optimal Min/Max subdivs to keep your GPUs busy all the time, so you don't need to care about subdivs at all.

[Muhammed_Hamed]

Very interesting!
Thanks for the input Alex!
So the difference is just the UI and it is using some kind of forumla to figure out Min/Max subdivs based on that, is this how it works?
Or the sample limit parameter goes deep into how Vray GPU works?

Say I want to export a Vrscene to render with standalone, or with Chaos Cloud

[a7az0th]

The difference is just the UI and we use formula to calculate Min/Max subdivs that would keep the GPU well utilized. On GPU getting Min/Max subdivs wrong can be devastating on performance, so we have taken the opportunity to calculate good default values for you based on your quality settings.

[Muhammed_Hamed]

Awesome Alex! This makes a lot of sense.
It is definitely easier for us to have samples limit, instead of min/max Subdivs, and it is idiot-proof so people don't use bad settings(even though defaults are optimized for most cases)

Cheers!

[Karol.Osinski]

With progressive mode you need 100 max subdivs and .01 noise threshold

Hey Muhammed, what is the reason for 100 subdivs for a progressive sampler?

[Muhammed_Hamed]

Hey Muhammed, what is the reason for 100 subdivs for a progressive sampler?

Hi Karol,

In my testing I have found 100 Max subdivs to give the best results, it is the default value so you only need to change noise threshold to control noise vs quality
This way you are making it easier on yourself, having to play with a single slider for all sampling settings.
And like I said above, bucket mode is very smart and in many cases faster than progressive mode, it gives you cleaner results if you use the same noise threshold
This is because Vray can determine the right amount of samples within each bucket, which is more efficient than adding more samples each pass and you end up with noise that takes longer to resolve
With bucket mode in most cases 50 max subdivs should be enough,
I don't recommend going below that, again my workflow is using noise threshold to control noise/speed
And generally speaking using low max subdivs some areas might get cut off and you get uneven noise in your render.. it is a much better workflow to stick to say 50 max subdivs and rely on noise threshold for controlling noise