"Devide shading subidvs" leaves Vray working linearly? Is this correct?

[Dariusz Makowski (Dadal)]

Ok, so with contrasty HDRI map, i got same results with MentalRay... means with increased sampling, i observed improvement in quality and growth of rendertime.

Now, i tried Vray with same high contrast HDRI, and i observe the same as before. With increased sampling, i observe improvement in quality and decline in rendertime, up to some point, where rendertime starts to grow again due to the wasting of samples.

I am quite confident when you did your tests with Mental Ray, you mixed up your results somehow. Otherwise i can not explain it. I am attaching the Vray version of scene with high contrast HDRI, and HDRI map used in this scene can be found in the Mental Ray version of the scene in the post above

Its not only with IBL. Its the same way with Materials and normal lights.

Basically the way I see vray with samples is

1 - not enought samples >noisy light/material> AA takes over cleaning of images > Long render times
2 - Just enought samples > smooth light/material > AA dont take over cleaning of images > faster render and cleaner
3 - Too much samples > smooth light/material > AA dont take over cleaning of images > Longer render times due to oversampling.

Then again I'm probably totally wrong :- )

Best way is to look at sample rate pass. If you have red in other areas than complex contrasty textures and edge of geometry then you are wasting render time using AA to do the job of materials/lights due to lack of samples.

[Lupaz]

Vlado, "min shading rate" is AWESOME!!!!

As RockinAkin said before:

I do think Vlado is right that simply using the Min Shading Rate is the best way to quickly balance your scene's Image and Shading samples.

[Lupaz]

As you know, we always want more.
So I'm thinking that it would be nice that the global subdivs multiplier came after the samples division. That way we can control the balance between AA and samples with min shading rate AND, if we need more samples (less noise in shading) we can add them with the global multiplier.

I'm just throwing it out there...

[LudvikKoutny]

As you know, we always want more.
So I'm thinking that it would be nice that the global subdivs multiplier came after the samples division. That way we can control the balance between AA and samples with min shading rate AND, if we need more samples (less noise in shading) we can add them with the global multiplier.

I'm just throwing it out there...

Sure, let's also add "supersample subsampling sampling checkbox" it would first subsample the image, and supersample the subsampled image to get back to the original resolution. It wouldn't really make much difference, but it would make you feel like you are doing some tech wizardy stuff.

No, seriously, if Vray needs something, it's actual removal of sampling setting, and automatic handling of them, instead of adding new ones. If another set was added, i would probably ditch Vray for good.

Now, back to the topic. I am not complaining that i can get higher quality out of Vray, while making rendertime even shorter. That's an awesome thing. But the problem is, that you can get very noisy and ugly images, with high rendertimes. That should not happen. The quality of image (technical one, like amount of noise) should IMO always be reflected in the rendertime. Even now, after the tests done above, i still have feeling that i do not have full control over what Vray does with sampling and i still can not optimize the **** out of my renders, which i was usually able to do with Mental Ray. Divide shading subdivs option feels like a partial placebo. While it makes something behave differently, it still does not seem to leave full control over sampling up to me

[Dariusz Makowski (Dadal)]

Sure, let's also add "supersample subsampling sampling checkbox" it would first subsample the image, and supersample the subsampled image to get back to the original resolution. It wouldn't really make much difference, but it would make you feel like you are doing some tech wizardy stuff.

No, seriously, if Vray needs something, it's actual removal of sampling setting, and automatic handling of them, instead of adding new ones. If another set was added, i would probably ditch Vray for good.

Now, back to the topic. I am not complaining that i can get higher quality out of Vray, while making rendertime even shorter. That's an awesome thing. But the problem is, that you can get very noisy and ugly images, with high rendertimes. That should not happen. The quality of image (technical one, like amount of noise) should IMO always be reflected in the rendertime. Even now, after the tests done above, i still have feeling that i do not have full control over what Vray does with sampling and i still can not optimize the **** out of my renders, which i was usually able to do with Mental Ray. Divide shading subdivs option feels like a partial placebo. While it makes something behave differently, it still does not seem to leave full control over sampling up to me

Just set adaptive amount in dmc settings to something like 0.0 or 0.5 and you will get ur control back.

[LudvikKoutny]

Just set adaptive amount in dmc settings to something like 0.0 or 0.5 and you will get ur control back.

Tried. Nothing changed. Pattern remained pretty much the same.

[Dariusz Makowski (Dadal)]

In what pass do you get the noise? Raw - refl/refr/light/gi/?

[LudvikKoutny]

In what pass do you get the noise? Raw - refl/refr/light/gi/?

Come on

I am not trying to optimize my render. I know how to do that. I am trying to prove that divide shading subdivs checkbox does not completely do what it should. It's irrelevant if noise is in direct lighting, gi, refl, etc... What's relevant is that disabling of shading subdiv division should prevent AA sampler from trying to compensate for that noise

[Dariusz Makowski (Dadal)]

Humhhh so disabling subdiv and setting adaptive amount to 0 is not doing this for you? :/

[LudvikKoutny]

Humhhh so disabling subdiv and setting adaptive amount to 0 is not doing this for you? :/

Nope, but you can try yourself. I attached several example scenes in my posts above

[joconnell]

Come on

I am not trying to optimize my render. I know how to do that. I am trying to prove that divide shading subdivs checkbox does not completely do what it should. It's irrelevant if noise is in direct lighting, gi, refl, etc... What's relevant is that disabling of shading subdiv division should prevent AA sampler from trying to compensate for that noise

Hmm, I don't know if that's really the case. The AA sampler will always try and clean up whatever noise there is between the 2d pixels, it's in a way not aware of what the dmc sampler is doing and only operating on the combined results of light, material and gi sampling. Rendering goes initial ray > dmc sampling (mat / light / gi) > combine dmc results > Back to the aa sampler to judge based on colour thresh. There's no way to kind of decouple AA sampling from judging the noise of materials for example and "compensating for noise" as you say it, the aa sampler is almost kind of working on a 2d image so the noise and colour threshold between each pixel is pretty much the only thing is has as information to work on.

What Dadal is suggesting will remove vray from making adaptive decisions (and of course lose a lot of speed benefits) but you're right, I don't think it's possible to do what you're asking and I'm not sure why you'd really like to do it either

[LudvikKoutny]

Hmm, I don't know if that's really the case. The AA sampler will always try and clean up whatever noise there is between the 2d pixels, it's in a way not aware of what the dmc sampler is doing and only operating on the combined results of light, material and gi sampling. Rendering goes initial ray > dmc sampling (mat / light / gi) > combine dmc results > Back to the aa sampler to judge based on colour thresh. There's no way to kind of decouple AA sampling from judging the noise of materials for example and "compensating for noise" as you say it, the aa sampler is almost kind of working on a 2d image so the noise and colour threshold between each pixel is pretty much the only thing is has as information to work on.

What Dadal is suggesting will remove vray from making adaptive decisions (and of course lose a lot of speed benefits) but you're right, I don't think it's possible to do what you're asking and I'm not sure why you'd really like to do it either

Simply because i want to have control over sampling. The entire point of divide shading subdivs checkbox is to prevent what you described from happening. If the checkbox is enabled, the compensation should happen. But if disabling the checkbox does not completely disable compensation, then the presence of that checkbox is completely pointless. In some of other renderers, i have control over sampling without any significant compensation going under the hood.

Usually, when i do an animation, i set up my scene according to my experience, then i render ahead, and i get a good quality for a good time. Say fullHD frame of non-trivial scene in 30 minutes. Now, when i was using Mental Ray, and i told myself, that i will try to squeeze some better time out of it by breaking sampling of my scene down to it's elements, and tweaking them, i could do so. It was not even a complicated process. Usually took me 15-30 minutes on average, and paid of by saving say 12 hours of render farm time. I was able to cut of let's say 30% of rendertime, while retaining same quality.

Now in Vray, i generally get better rendertimes for same quality. Vray is just overall better renderer. But any attempt on optimizing Vray scene is equal to stepping on a rake. I initially get let's say 30 minute render with a good quality. Then i decide to optimize it. I start to break it down, hunt down noise. Increase AA noise threshold higher, and compensate with local shading subdivs of lights and materials. I tweak everything as best as i can. Sometimes spending hours just on that. Then, being proud of how i broke everything down, and analyzed it, i render whole frame again, and i get same rendertime, with same quality. Vray always finds it's way to prevent me from optimizing anything.

It may be a good thing, as while i am never able to get exceptionally good rendertimes, i am also unable to get exceptionally bad times. That's what could be called reliability. And i am sure many people who just want to make nice images without need to becom tech guru will appreciate that and love vray for that. But since i spent years learning and understanding mechanics of rendering and how to put it to good use, i would like if i could apply that gained experience when using Vray without being prevented from doing so by some internal compensating mechanism.

Of course, i am not implying rendering should be something technical. I would like to see many sampling settings from Vray's rendersettings UI gone. But at the same time, i know there's a lot of things going under the hood of Vray which are not optimal. I would love if only sampling setting in Vray was noise threshold, and all the rest was gone, including subdivs from lights, materials, etc. Something like what Corona does. But if i actually have to tweak sampling of every single scene component, like i have to do now, then i would at least like if it worked predictably.

[Lupaz]

I'd be very interested in an uncoupled AA too. (If at all possible)
I think we all went through what Recon describes. In some cases it would be good to turn V-ray's "automaticallity" off for a while.


And I think this is key:

I would at least like if it worked predictably

.

[joconnell]

Simply because i want to have control over sampling. The entire point of divide shading subdivs checkbox is to prevent what you described from happening. If the checkbox is enabled, the compensation should happen. But if disabling the checkbox does not completely disable compensation, then the presence of that checkbox is completely pointless.

Ah okay, it might be that you're thinking that "divide shading subdivs" does more than it really does. All divide is doing is preventing vray from dividing subdiv settings by your max aa number, so it's kind of hiding a ui thing in an attempt to stop you having enormous ray counts, it doesn't however change the way vray will work towards final quality in terms of the colour threshold and how your aa samples deal with the results of your DMC samples.

If you got what I think you're asking for which is having your AA quality totally decoupled from your dmc sampling, you'd first have to figure out how the aa sampling is going to base it's quality decisions on. Will it be the normals of an object? Will it be colour values that comes back from it's sampling? If the two didn't talk to each other at all and left all the control up to you I could see vray trying to make decisions on very little information and giving you some pretty bad results and nasty render times.

[LudvikKoutny]

Ah okay, it might be that you're thinking that "divide shading subdivs" does more than it really does. All divide is doing is preventing vray from dividing subdiv settings by your max aa number, so it's kind of hiding a ui thing in an attempt to stop you having enormous ray counts, it doesn't however change the way vray will work towards final quality in terms of the colour threshold and how your aa samples deal with the results of your DMC samples.

If you got what I think you're asking for which is having your AA quality totally decoupled from your dmc sampling, you'd first have to figure out how the aa sampling is going to base it's quality decisions on. Will it be the normals of an object? Will it be colour values that comes back from it's sampling? If the two didn't talk to each other at all and left all the control up to you I could see vray trying to make decisions on very little information and giving you some pretty bad results and nasty render times.

I understand,

but I do not know specifics about this. I do believe it's not as easy as just "decoupling AA from subdivs". There's probably something a lot more complex going on in Vray core. So it may even be impossible to do so. I do not have any specific solution how to do it. I just posted both Mental Ray and Vray scenes to illustrate the difference, being apparent that Mental Ray can do it - somehow.

My point is:

If image A is very clean, and takes 10 seconds, then why image B, which is very noisy, takes 10 seconds as well. You need a lot less rays shot to get such a noisy results. It's as if Vray told you: "Hey, i want you to render it in 10 seconds, not more, not less. If you decrease sampling, you will get noisier image, but i will still make sure it takes those 10 seconds!"

I was very disappointed when Vlado say that we "whined" about it, and then the checkbox he gave us did not help at all. Of course it did not, because it does not do what we wanted it to do. If it's not possible to really decouple AA from subdivs in Vray, then we should have been told it's simply a core limitation and that it's not possible, instead of being called whiners responsible for that redundant checkbox.