Motion blur subdivs ( physical camera)

[igordesign]

Very nice Komposer,thanks!, whats the process you use to get this settings?
You set the image sampler min. and max. using samplerate pass? After it you set the shaders and lights subdivs?
when i set the min. shading rate?

[Komposer]

Hi Igor,
please take a look in these youtube tut from Grant Worwick.
https://www.youtube.com/watch?v=pak8wx7KNEA
For me the best one, for understanding these prozess - and only 30min!
The center of all is the RenderElement "Sample_Rate"
Beleave me, after some tests it become to make fun!!!!

Here a totaly short overview (in the tut much better), from someone who try to understand that things sinse 3Years - but hopefully now!
1. in renderglobals switch off lights (only default keeps on), shadows, Ref and glossy...
... switch off GI for the moment
... switch off MB for the moment
(in Your scene defaults lights will not work, no idea why)
2. add for Your scene renderElements lighting, shadows, GI, reflection, specular
3. start with AA 1,8, 0.01 (min shading rate at 1)
4. Render it at 960 - not HD, its too slow for tuneing
5. Take a look onto "SampleRate"
You´ll see many red, yellow, orange, green and blue regions
What SampleRate says "everything which is not blue becomes more and more AA samples", and all in red becomes max samples!
But AA Samples we need only at/for object boarders, textures, DOF and motionBlur - AA Samples = primary Rays
As example - The Fan needs for a nice highQuality result at the boarders of the wings high AA (more red) but on the big planar faces with no tex, no AA!
So when your wings are full of red, orange, green, etc. there happens many CPU-time for nothing!
Because of...
What on the wing faces happens are "secondaryRays", like light, shadow, reflections, glossy reflection, GI, etc.
And all these things are only tuned inside the lights and shaders.

6. now increase max samples onto 12 and look onto the sammpleRate
The result become more blue and less red and green - and a faster rendertime!?
7. try with higher max, perhaps 16 and the most red ist gone.
I think that means: red with AA 1/8 means, 8 samples are used - orange with AA 1/16 could mean, that 8 samples are used too. So the AA HQ result could be the same
Try it with max 32 and You´ll see that sampleRate becomes nearly complete blue and the AA edges becomes more noisy and not so good!

Now, with max 16, switch on motionblur and check if it´s nice enough too.
Try 14 or 18 and decide what is the best for You.
Later You can increase quality by decrease adaptive treshold from 0.01 to 0.009, .008, .007, and so on.
But for now, we say 16 with 0.01!
And dont touch max samples fom here on.
Primary Samples/Rays are fit!

8. In the glabal renders switch on lights and shadows
Solo all your 3 lights one by one (use the nice new light editor from vrayTab-it´s cool and very handy)
All subdivs starts at default 8.
Render with light 1.
Check sampleRate - red, orange, green comes back.
Check light and shadow pass - very noisy.
(and this is the reason, vray activates primRays/AA, because of too much contrast from one noisy pixel to the next. Vray think´s its a boarder, or a bright highlight, etc.)
8. increase subdiv in bigger steps (I mean, thats a good idea to use, when max is 16 - 32 or 64, or 80, 120, 160, 240, 320 - a multiple of 16, but im not shure)
The noise become less and less and the render speed becomes faster and faster!
...because of vray now don´t think, that here we need AA!
But if Your settings are too high, the speed don´t get faster and the noise becomes not so good again.
(You´ve to play a bit arround for the first)
9. Swtich off light 1, switch on light 2 and repeate the steps - for light 3 the same.
Now lights subs are finished.
10. in renderglobals switch on reflection and glossyEffects
The shaders have default subs at 8
Render and take a look on sampleRate: red, orange, green comes back - the same reason like the shadows and lights
Increase ref subdivs to 64, or 96, 160, etc...
When You´re happy with ref and specular and grain of glossy.....
11. Switch on GI, render and check the renderElement GI for noise.
Startpoint is 8 (in Your scene, I ment 8 was enough, but it´s Your choise

I hope, I didn´t forgot too much, or didn´t discribe it too far away from reality
What I said, for years, I didnt understand that theme and was vey said about that.
Perhaps weeks of rendertime gone in past

If there are any comments of my intepretation - great

btw.
a. the "Min Shading Rate" isn´t a thing what I understand in this moment.
I ment to see a bit finer rendering in noise, when I set it fom 1 to 25, but for the frist I would beleave it at 1!
(to set it to 6 - nothing happens!!!)
b. the use the "vray object subdivisions" instead of smoothing the lowPolys isn´t a good idea here.
I tried all, with max divs of 16, 8, 4, 2, ...
...the rendertime becomes much longer!
c. to use the carpaint shader makes 20-30% of rendertime, I think - don´t know why - I use it nearly zero
...but it looks on the propeller so much better than the normal vrayMtl
d. never before I needet motion blur in such a format filling case.
...but in Your case, I would try to render motionVector RE and do the MB inside post...
In my tests, the MB needs minimum 70% of render time!
e. I would try to use a HDRI instead of Your, lights, stage and GI.
...made in HDRI studio, as example, Your visible result could be the same...
...or try one of the endless free images....
...and You can save many many render time - but I didn´t try that...

Would be fine if this could help a bit.
Cheers, Jörg

[igordesign]

I thank you very much for your explanation, I use this same method to get a good result in the shortest time possible in my scenes. But I also could not understand min. shading rate. I agree with you that the motion blur in the case of this scene, is the evil of history.
when i finish this job, im upload a final result here

[igordesign]

Hi friends, sorry for delay, this is the final job, my task on this job is the fan scene
Thanks for your help

https://vimeo.com/152457409