Any way to specify local subdivs for Mblur or DoF in 3.3?

[Intuition]

I still like to tune the sampling/subdivnumbers for motion blur and DoF myself.

At the moment I feel like I am upping the whole scene when I just need a little bump in certain areas.
Where as in previous Vray for Maya versions we had control of these two things.

Thanks for any info.

[yolov]

You can use vray object properties and override the motion blur samples. I'm not sure if there's a way to do this for DoF, since vray uses AA samples for it.

[Intuition]

Well I mean yes I can set vray geometry samples per object using the vray object properties but I can't ste the actual pixel sampling as was available in the older Vray 2.4 or 3.1

Same for DoF. You can reduce noise <--> gain speed based on the subdiv settings from before. Vs having to up all the render engine adaptive levels.

[joconnell]

It's your max aa samples - it turns out that the dof or motion blur samples were setting the exact same thing. I reckon what was happening though is your material and lighting subdivs were only being divided by the number that was in the image sampler section and not the higher number being put into your camera settings, thus you ended up with higher quality shading as compared to what'd happen if you used the max aa setting to set your blur and dof quality.

[Intuition]

Well in the older Vray you had a separate subdiv for motion blur specifically. This would allow me to have a min max of like 1 and 4 and a threshold of .007 and just turn on motion blur and make the samples somewhere between 12 and 16 and I would get clean motion blur without spiking my render times very much. Now I raise the max up to 12 and it exponentially raises the render time. I feel like I have less control now in vray 3.3 than I did in 2.4.

Does the attribute still exists in the background I wonder. Like if I set the attr with MEL?


---edit----


Ah wait, I see it here on the vray settings node hidden. Yeah I can set them here.

setAttr "vraySettings.cam_mbSubdivs" 16;

Hmm no doesn't seem to impact the quality, Must really be the camera motion blur.

[joconnell]

There's the same attribute in max but unfortunately it doesn't do anything anymore.

If my theory is right for your case, you'd have set your aa to 1/4 and your motion blur to 12 or 16. What was possibly happening was more to do with your shading samples than the aa ones. As we know, vray 2.4's behavior was to divide up your shading samples evenly between the aa steps so you wouldn't end up with the same ray explosion and exponential render times common in other renderers. So with your aa 1 / 4, all of your shading settings in your lights (lets say they were all 48 for the sake of easy numbers), materials and gi were getting divided by 4 so with each aa step you'd get 48 / 4 or 12 shading steps. In vray 2.4 when you started to use motion blur or dof subdivs, all that was happening was you were increasing your max aa to a higher number. I think (I'd have to test this) the difference was even though you were raising your max aa, your shading settings were still only getting divided by your max aa number, so you were getting max aa of 12 as you'd set, but each of those aa steps were still getting our 48 / max AA 4 = 12 shading steps. The division didn't kick in as much. You'd have 12 rounds of aa and each would be getting 12 shading steps.

Now in vray 3 where there's no dof or moblur subdivs, we have to use the max aa value to clean up our motion blur or DOF, and if we up the max aa value, that WILL divide our shading steps more compared to the old behaviour. So again in vray 3 if we up our aa from 1 / 4 and 48 shading samples to 1 / 12 with 48 shading samples, the issue is that our 48 shading steps now gets divided by 12 instead of 4 so you're getting 48 / 12 = 4 shading steps per round of aa. This is a hell of a lot less than you used to get in vray 2.4 and I reckon that might be what's causing the difference.

How are you setting up your shading samples - are you using local stuff per material / light or are you using the shading rate?

[ivaylo.ivanov]

The mblur/dof subdivs were completely removed since they are really part of the image sampler. If you want, you can send the scene to the support for testing, but it should be possible to get similar rendering times.

[joconnell]

Ivaylo, am I correct in thinking that vray 2.4 only divided the shading samples by your max aa image samples and never by whatever you set in your dof or motion blur subdivs and thus the main difference is that vray 3 is just dividing your shading samples more heavily since we now end up a higher number in the max aa to clean our dof / motion blur edges?

[ivaylo.ivanov]

I think you are right, the old controls were using their own DMC logic.

[joconnell]

Great - it should be fairly straightforward to figure out what you'd need to set in vray 3 to get the same ratio of aa and shading samples from 2.4 then - thanks!

[Intuition]

I did have the use local subdivs turned on because that is how I am used to tuning Vray.

I turned it off and the renders went quite fast. I went from 2:32 to 24 secs. Then I raised the min max to 1- 12 and it was quite clean in the motion blur as well.

What I am not understanding is how when I have "use local subDivs" on that it takes so long for Vray to draw even simple diffuse surfaces. Seems like it is taking a longer time than before with similar settings.

I have a dome light that was at 24 subdivs and one area light at 16 subdivs and just diffuse surfaces and it was taking the render quite a bit of time at 1-4 min/max and .007 threshold.

I don't understand why there is a large render time difference than even 3.1 or 2.4 in this case. It should be 20-30 seconds at most since it is just drawing diffuse surfaces and giving a little time to the soft shadowing of the dome and area light.

I can keep use local subdiv off but then it feels like I am letting go of the tuning and just handing it off to Vray to tune for me. I never change the dmc from .850 at min 8 or maybe up to 12 samples much anyways except for rare contrasty reflection glossy cases.

use local subdivs seems like the path to the old shader/light tuning I am used to but produces slower results than I used to get. So I guess I need to just switch everything over to tuning with min/max but it feels more like arnold or renderman now where you just turn up the quality slider and throw your hands up and go. ..."it just takes that long".

Any insight into tweaking per light/per shader/ Mblur/ DoF / displacement etc etc to get best render times with new UI appreciated.

Forgive my inquiries. I was quite used to, and relied upon to, using Vray with exacting render time optimization understanding and now its starting to feel less hands on.

Thanks for everyone's help.

[t.petrov]

One way to see why it is taking longer is to compare the numbers of rays V-Ray has fired.
The info is printed in the log at the end of each render.

Generally people have been complaining about the opposite problem - it is too hard to tweak renders in V-Ray, because there were too many parameters to tweak.
By using "use local subdivs"=off we've removed most of the parameters and as benefit most of the times the performance is the same or better.

In newer V-Rays you're supposed to tweak min/max subdivs; min_shading_rate and the noise threshold and nothing more.

[joconnell]

I did have the use local subdivs turned on because that is how I am used to tuning Vray.

I turned it off and the renders went quite fast. I went from 2:32 to 24 secs. Then I raised the min max to 1- 12 and it was quite clean in the motion blur as well.

So there's one answer or way of looking at it. If you're happy with the new render times and the images are clean enough with the simpler way of setting quality then great! Vlado's ideas for the new setup are very much spend less time tweaking and move on to the next shot.

What I am not understanding is how when I have "use local subDivs" on that it takes so long for Vray to draw even simple diffuse surfaces. Seems like it is taking a longer time than before with similar settings.

Yeah I think that's the big issue here - as I mentioned in my last reply I think the logic has changed a tiny bit - whereas before with your 1/4 and 12 dof samples vray was dividing all of your shading settings by your aa 4 but rendering the image with your dof aa of 12, now since that control is gone vray's now dividing all your shading settings by the full 12 - it just means with the same settings but with vray's new way of calculating things, you're getting less shading samples per aa round than you were before. I'm going to do a bit of a fish into it, it's only one change so I reckon we can figure out a method of working out what you used to get and how you'd get the same in vray 3.

Forgive my inquiries. I was quite used to, and relied upon to, using Vray with exacting render time optimization understanding and now its starting to feel less hands on.

Yep I getcha. If you want to keep working like you did in 2.4 there's only one change - we'll get it figured out and you can have it as another option while the vray devs keep making the sampling smarter and smarter.