Max Depth setting

[Svetlozar Draganov]

As in if you've a light with 8 samples and dmc aa 1 / 4, when vray fires it's first set of rays at aa level 1, does vray always use the light subdivs divided by the max aa? As in regardless of what level of aa sampling from 1 to 4 it's at it'll always be using 2 light samples per eye ray?

When we are talking about samples in Vray we always mean Maximum Samples - not actual samples.
If you have 8 light samples , and AA DMC 1/4 - Vray will fire Maximum 8/4=2 samples per camera ray, but since the absolute minimum samples in DMC SAMPLER (not DMC image sampler) is 2 - as a result Vray will shoot exactly 2 light samples per camera ray - because minimum and maximum samples per ray in this situation is 2.
If in the same example we have default minimum samples value - which is 8 , Vray will always fire 8 samples per camera ray regardless "calculated" maximum samples = 2.
Please have in mind that I mention only "samples" here not subdivisions. The parameter in Light options is called "subdivisions" - this is important to know because if you enter 8 in this field you actually set 64samples = 8x8.

[joconnell]

Yep I getcha - I wasn't sure whether vray was changing the amount of division it was doing to your samples / subdivisions as it walked up from min to max aa sampling or whether it made one decision right at the start - thanks for clearing that up!

So with the minimum dmc samples that also accounts for why reducing some samples makes no difference - the minimum samples is acting as a lower clamp value? I take it that 8 samples was chosen as a minimum for a similar reason to vlado not liking using 1.0 as the adaptive amount value - anything less than 8 samples isn't enough information for vray to make a good decision on for further sampling?

[Svetlozar Draganov]

anything less than 8 samples isn't enough information for vray to make a good decision on for further sampling?

Yes that's correct - of course for test renderings you can decrease this value in order to get more speed - but in production rendering it is not recommended to use less than 8 samples.
The same thing apply to Adaptive Amount =1 , it is good for test renderings - but you don't want to clamp all subdivisions to a very low value for your final render.

[joconnell]

Interesting!

So in that case the 8 samples that materials and lights have by default are almost irrelevant? If pretty much any aa over 1 is going to divide the samples below 8 and the minimum samples will bring it back up to 8 samples anyway then the default 1/4 aa means that you really have to start bringing your material or light samples over 32 (at aa 1/4) before you'll start seeing any meaningful difference?

[Svetlozar Draganov]

The Default Samples in Material and Lights are 64 - not 8.
This is very confusing some times - in almost everywhere you have SUBDIVISIONS , the only place you have samples is "minimum samples"
In all places where you have Subdivisions - this is the square of the samples value:
subdivision*subdivision = samples

[joconnell]

Ah, duh on my part once again, I should really read your posts once, then another time, then a third time just to make sure I properly understand it

Thanks again for the knowledge!

[Svetlozar Draganov]

Don't worry - we are here to help you
Fell free to ask any questions that you need to clear for yourself.

[joconnell]

Much appreciated Svetlozar, you're a brilliant addition to the forum!

[maxedesa]

I'm having a similar/related problem...

Max depth in the material settings reacts totally differently than the Global Switch. See the following images with notes.
(For the simplification I've turned off reflection for the glass material.)

[MoonDoggie]

Caleb, you found my thread! I am still a bit fuzzy on this too.

I believe what we found out is that the "Max Depth" setting on the globals sets all materials to whatever you have set there (regardless if they actually need none at all). It is not a clamp in the sense that "you can go lower, but don't exceed this value", but it's a "use this many bounces for all materials". I believe is what we found out.

-Colin

[maxedesa]

Pretty sure I understand what you are saying, but does that explain the images? Why should the global 25 make any difference in the image if the material is already set to 25?

[MoonDoggie]

That is a good question. I'm still not 100% on the answer I got to this question honestly.

[Neilg]

What dont you understand about it? There is a global max depth setting which overrides all of your materials.

Pretty sure I understand what you are saying, but does that explain the images? Why should the global 25 make any difference in the image if the material is already set to 25?

Are you looking at those through a piece of glass which doesnt have the refraction depth set to 25? If you've got something with a value of 25 behind something with a value of 2, it will only use the 2.

[Svetlozar Draganov]

I'm having a similar/related problem...

Max depth in the material settings reacts totally differently than the Global Switch. See the following images with notes.
(For the simplification I've turned off reflection for the glass material.)

[ATTACH=CONFIG]13289[/ATTACH][ATTACH=CONFIG]13290[/ATTACH]

Cubiclegangster is right , something is wrong with the image with Global Max Depth OFF , if all materials refraction depth is 25 I would expect to see image similar to the second one.
Is it possible to attach this scene ?

[maxedesa]

maxDepthProblem.zip

Being a new day with a somewhat refreshed brain I've found what is likely to be the problem - the mirror behind it - had a reflection depth of 5. So I guess the glasses were turning black because they were reflecting back and forth with the mirror. I'll attach the scene anyway, in case you want to see.

In attached scene I'm leaving mirror depth at 5 (which causes problems) and global depth unchecked (which, when checked, fixes it).

Caleb