Set up Passes (Vray GPU)

[Dmerc]

I am sure this has been discussed - sorry - but I can't find it:

I am trying to optimize rendertimes in Vray GPU:

Setting samples limit to 6 results in 16 passes
Setting samples limit up to 14 also results in 16 passes.
Setting samples limit to 16 and above suddendly gives hundreds or thousands of passes.

What do I do if I "know" that 40 passes are sufficient?

I have been toying with the Rays per pixel, but there is no logic pattern that i understand.

That said why is it not possible to just input the real pass-limit?

Thanks for your response in advance,
Peter

[vladimir_krastev]

Setting samples limit to 16 and above suddendly gives hundreds or thousands of passes.

Why do you deviate that much from the default value? The margin is much bigger for this parameter. If you have 6 or 60 as a value here you are just scratching the surface.
Try to compare a Samples limit of 2000 versus 10000 for example.

if I "know" that 40 passes are sufficient

How would you know that? Even if you did what is important is the render time and the noise amount. You could limit your render by time if you prefer.

Here is a list of articles that you may find useful.

[Dmerc]

Why do you deviate that much from the default value?

Because with a default value of 100 I can get sample rates of up to 10000 with very little visual imrpovement and potentially long render times.The noise value helps, but in some cases it is not really "capping" the rendertimes leaving Vray dealing with single leftover spots for considerable times.

How would you know that?

By doing render tests and judging that around x number of passes I do have a good balance of times vs quality for that shot . Please understand, some people have a small setup + deadlines. Even after 15 years of using Vray I still struggle to get control of the sampling.

You could limit your render by time if you prefer.

That does not work if you have multiple machines working on a job with different setup. Even doing this on a single machine I had frames with only one pass because whatever happened on that machine.

Anyhow, still would have loved to have a simple max-sample spinner - is there some technical limitation, why this is not a good idea?

Thanks for the link, will see if it gets me somewhere.

[Joelaff]

Can you not get similar results by finding the noise threshold that stops around the desired number of passes? It may be something like 0.25 or something in that larger range.