Max Depth setting

[MoonDoggie]

Vlado,
I've found some strangeness with regards to the max depth setting in a vraymtl. If you clamp this value globally (V-Ray Globals) at 5, and have materials with it set to the default 10 it will render slower than if you go through all the materials and change the max depth to 5 in each...

Can you verify this on your end?

-Colin

[Neilg]

It doesnt clamp it to 5, it sets everything to 5. I assume you also have some materials lower than 5 which it's lifting up, making for longer render times.

[MoonDoggie]

That's what it should do yes. All of my materials are set to 10 max depth in my scene.

Now: With all scene materials set to 10 in their max depth, now set the global max depth to 5 and render, record the time.

Now, go through all materials in the scene (with VMC or whatever you like), and clamp them each to 5 max depth, render, record time (in my tests, it's taking 20m less for a 1.5hr render...)

[Neilg]

I just did a test with some glossy reflective objects inside a mirrored sphere and it works as expected.

Max depth 10 - 4:41
max depth 5 in global - 1:18
max depth 5 in material - 1:19

[MoonDoggie]

Not quite. did you test the max depth (in material) at 10, but changing the max depth to 5 in global? That's what I'm saying...

[svetlozar.draganov]

I couldn't produce it either. In my tests the result from Global Switches set to 10 is slower than the result with 10 set from Material with 0.1 second.


1. Material_Max_100_RenderTime_3m6.9s
2. Material_Max_100_Global_10_RenderTime_1m14.5s
3. Material_Max_10_RenderTime_1m14.4s

1.2.3. reflection_limit01.zip

If it is possible please attach example scene.

[joconnell]

It doesnt clamp it to 5, it sets everything to 5. I assume you also have some materials lower than 5 which it's lifting up, making for longer render times.

Wow, that I did not know. I assumed it was max depth i.e. a clamp - that's what the naming implies. Good to know now though, free render speed increases for me!

Ah - it's not on by default anyway. Boo, no render speed increases for me :/

[Neilg]

Not quite. did you test the max depth (in material) at 10, but changing the max depth to 5 in global? That's what I'm saying...

Thats exactly what I tested - the max depth 5 in global test had 10 on the materials.

Wow, that I did not know. I assumed it was max depth i.e. a clamp

I don't know anyone who didn't assume this - myself included. bad memories of trying to speed up renders by clamping it to 3/4, and having renders take longer because all the leaves just got a few more bounces

[joconnell]

Interesting one though, I rarely go over 5 on anything for starters and now I'm using a script to set bounces based on glossiness - this could be a handy one to see what the benefit of the extra bounces is before / after, especially if you're not using glass or refractions in a scene.

[MoonDoggie]

Svetlozar/Cubicle, thanks a ton for testing this. Let me test it again on a substantial scene and get back with you. Also, thanks for the info about the global max depth. What are you saying about renders taking longer because you clamped it at 3/4?

[joconnell]

I presume he means he had leaf reflection bounces at 1 or 2 and had other materials at 5, but setting the global limit to 3 or 4 to try clamping reflection bounces on all the other materials mean that his leaves were also set to 3 or 4 bounces instead of just 1 - nasty!

Actually Svetlozar on matters of bounces and samples - I wanted to clarify something on the DMC methods also, when you're setting subdivs on a material or light, does the number of subdivs get automatically divided by your DMC max aa number full stop? 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?

Sorry for derailing your question Colin!

[MoonDoggie]

Ah-ha! I wish this setting were implemented as a clamp instead of how it is.

[joconnell]

Yeah it's a slight bit of mislabelling isn't it?

Actually on this note does this set the same number for both reflections and refractions? As in if you turn on a max depth of 4 does that mean that reflections and refractions both get 4 bounces? Or does it mean 4 is shared between reflection and refraction?

[Neilg]

Yeah it's a slight bit of mislabelling isn't it?

Actually on this note does this set the same number for both reflections and refractions? As in if you turn on a max depth of 4 does that mean that reflections and refractions both get 4 bounces? Or does it mean 4 is shared between reflection and refraction?

Both get set to 4.

Maybe we need another option under it - 'max, max depth'

[MoonDoggie]

haha. love it. Yes. 'max, max depth'