Going from 3.5 to Next - slow down

[devin]

I've upgraded to Next from 3.5 and of course the first thing I wanted to test was the speed improvements. I have a test scene originally created in Max 2016, it's made up of a bunch of Evermotion trees converted to proxies scattered around a ground plane using Forest Pro. I have a HDRI map in the environment slot linked to a Vray Dome light and there's also a vray sun and camera in the scene. When I render it with Max 2016 it takes 2m 12.5s at 1280x720, when I render the same scene in Max 2019 it takes 4m 27s. I've never had a scene render so solely on a newer version of Vray before, can someone please explain why this is happening? I've attached settings, they are the same in both versions.

[leo.surrealismo]

reset vray settings, and leave everything default.

[Muhammed_Hamed]

You have local subdivs on, which will slow everything down quite a bit.
Even in 3.5 and 3.4 you are supposed to leave it off in all cases.
Vray is smart enough to determine the needed samples depending on your min shading rate, max subdivs and nosie threshold
No need to assign any local samples..
Also you have subpixel mapping, affect background and clamp output on, which you probably don't need
And you have LC sample size set to .005 even if you are using 500 subdivs only.. which makes no sense
So, reset everything to default first, then use bucket sampler with max subdivs of 32 and leave everything else as is.
Use BF + LC default settings and set dynamic memory limit to zero

[devin]

I reset everything to default settings except for the max subdivs which I set to 32, total render time was better at 3m 44s but still not nearly as fast as my old settings with version 3.5 at 2m12s.

[glorybound]

Try literally resetting to default and try again. You'll have to change the render time, but leave everything else as default.

[devin]

Maybe I'm not resetting it correctly, I just switched between Scanline and Vray for my renderer, is that good enough?

[devin]

Ok I don't understand glorybound, I did what you said and my render time went down to 1m 2s, why?

[devin]

Sorry I got too excited, the default settings are set for progressive but I needed bucket, once I change this the times were the same as earlier 3m 46s.

[glorybound]

I have found progressive and bucket to be about the same in speed, however, you get to see the denoiser update along the way and you can stop it when you are happy. Are you using progressive as your productive renderer, or in IPR mode? IPR mode will change size with the VFB scaling.

[devin]

I use progressive when working but the final images are always done with bucket but if progressive is up to the task I wouldn't be opposed to using it. Right now I'm just trying to figure out why Vray seems to be slower, nothing I've tried so far has made much of a difference. Are you seeing speed increases of at least 2x over previous versions?

[glorybound]

I haven't compared the older versions and NEXT, side by side, but it sure isn't a noticeable decrease in render times. When I first upgraded I too said, "hey! my render times are a lot higher with NEXT". My interior times have gone bonkers, however, some have said that the increase in speed is awesome.

[Muhammed_Hamed]

I have found progressive and bucket to be about the same in speed

They produce different noise patterns, so comparing them you shouldn't rely on the same noise threshold of both. You should compare how clean both results are as bucket mode usually gives you cleaner result for the same noise threshold you use with progressive.
From my testing, Bucket is faster than progressive in many cases, up to 20% faster in some examples.
Thing is that Vray is very smart to assign the right amount of samples within each bucket, while in progressive Vray starts with few samples and it adds more adaptively where it needs too(that is why it requires max subdivs of 100 or so, compared to 24 for bucket mode). So progressive will struggle with fireflies in areas of contrast, SSS, refractions..etc
It will need a lot of time to clean this kind of noise.
This is not something specific to Vray and it applies to Cycles, Redshift and other renderers that have both sampler types.
Other advantages to bucket mode in Vray are better CPU utilization, more features like Cryptomatte , works better with DR and it uses way less RAM than progressive, because each rendered bucket is saved on your disk, while for progressive everything is kept in RAM until the end. You will be able to tell the difference with high res renders.

Are you seeing speed increases of at least 2x over previous versions?

From 3.6 to Vray next there is definitely a speed difference. Sampling of fog, hair, SSS, refraction and Dome light has been changed completely in Next.
In my testing, there is up to 25% speed boost with Vray next compared to 3.6, depending on your scene. And with Vray GPU next, it is up to 50% faster now.
As far as I know nothing should be slower in Next, so it is worth to report anything that you think renders slowly in Next.
For your case, the render settings you used are not correct even for 3.5 ,3.4 and 3.3 (3.2 and earlier is where we used to play with local subdivs and it was not really fun)
Like I said, you are supposed to never have local subdivs on in any case. Having it on, reverts to the old sampling workflow in 3.2 and earlier before Vlado and Lele came up with the magic sampling workflow that is currently been used in Vray and Corona
What I think caused your rendering to be faster in 3.5 is that you have 8 subdivs for Brute force GI and most likely something similar for your lights and materials.
This is going to affect your final render in many ways.
Can you post your 3.5 render that took 2 minutes with the render settings that you used and set everything to expert. And a sample rate render element will be helpful too
This way we will be able to tell why it was faster than next.
On the other hand, I can show you examples of how Next is way faster than 3.6 or 3.5 .. I have done many side by side testing since Vray next has been released.

[devin]

Muhammed I appreciate your help and I'll post those comparisons when I get a chance.

I understand what your saying about my settings being a bit wonky but I'd expect an older seen rendered in Next to be equal in speed if not slightly faster than an older version. Even using default settings doesn't improve the speed and it sounds like from glorybound's post that he's seeing the same thing.

[devin]

Here's the scene rendered in 3.5 with settings and sample rate.

[Muhammed_Hamed]

Hi Devin,
Thanks for sharing the sample rate pass in your 3.5 test.
Glorybound said that he didn't do any side by side comparisons yet. It just feels that render times are higher with Next.
Can you share the sample rate of your the same settings in Next?
Then one more test, using the default values in Next, change the min shading rate to 16 and light cache subdivs to 500
And noise threshold to .02
What render time will you get with these settings?