Raising samples on the light with the new sampling system? (noise in alpha matte)

[PIXELBOX_SRO]

Hi guys,

i am fighting with a noisy scene, especially with noise in alpha matte....its quite terrible.
Alhtough i had quite nice initial settings AA 1/100 and noise threshold 0.005, i had to to something quite ridiculous like AA 1/400 and noise threshold 0.001 to get clean shadows.
I tried to turn the light subdivs up but theyre all greyed out..
Am i missing something?

What woudl be the right procedure?

Also , i am gettgin shadows from HDR on the matted surafe all over the place.
I tried to use vray sphere fade but i am not too keen on that rapid fading it allows...either i have to make tha sphere large diameter or make it fade within its whole radius which affects the rendered object too making it see through (unless i render it twice with render selected).
I ve also tried knocking down the GI amount spinner in matte properties to 0 which kind of reduces the massive shadows to more acceptable size but the shadows are very very dark and unusable.

I am happy to post some images or send stripped scene of course if there is a need
Thank you very much for help

Cheers
Martin

[super gnu]

sounds like you have a similar issue to me. noise in alpha matte shadows. to me its a bug in the progressive sampler. nothing i did would clean the noise. switching to adaptive sampler and the noise is gone.

wrt the shadows all over the matte.. once the noise is gone, its less of an ugly issue, and you can render a mask for the non-matte objects then use that to separate the object from the matte, and play with opacity and masking of the matte in post.

[PIXELBOX_SRO]

yah i read your post.
In my case though, even swithching to adaptive doesnt get rig of the noise and all other artifacts i am gettgin there (even stuff like missign parts of buckets)
only turnign it waaaay up cleans it but then in PS you can still see bits of noise.

[vlado]

You can send a scene to me at vlado@chaosgroup.com and I will take a look.

Best regards,
Vlado

[PIXELBOX_SRO]

Hi Vlado yes i will.
anway, here is what i talking about.


scene is on the way
Thanks a lot!
M

[joconnell]

Hi guys,
Although i had quite nice initial settings AA 1/100 and noise threshold 0.005, i had to to something quite ridiculous like AA 1/400 and noise threshold 0.001 to get clean shadows.

Shadows are all to do with shading samples for your light - the aa won't help as directly.

I tried to turn the light subdivs up but theyre all greyed out..
Am i missing something?

Yep - so you're using the new defaults where "use local subdivs" is turned off by default and you rely on your minimum shade rate control for all those sampling bits - go back to your 1/100 and noise 0.005 and up your minimum shading rate to clean up the shadow.

[PIXELBOX_SRO]

Hi John, i raised MSR to somethign like 80 and it did not change at all.

[joconnell]

Yikes! Must have a go of something similar then and see what happens!

[PIXELBOX_SRO]

is there a way how to raise the light samples solely without affecting anythign else? - oh sorry its the use local subdivs...will check that

[PIXELBOX_SRO]

So:
Raising MSR actually makes the problém even worse, lowergin MSR to 1 makes it better.
settgin the AA to 16/100 and noise threshold to 0.002 while having MSR at 1 produces better results.

i am rendering it now so will post how the alpha and the final comp look.

However i am very surprised how complicated this is and i still downt understand why the alpha is loads grainier than the beauty pass.

Perhaps it woudl be good to have a multiplier in vray that woudl také care of alpha quality solely???
when you comp your alpha matte on plain color its very important to have mega clean alpha, especially in animation.

[PIXELBOX_SRO]

rendertimes are through the roof though....and its just shadow from HDRI, alpha and plain colored surface

[Morne]

rendertimes are through the roof though....and its just shadow from HDRI, alpha and plain colored surface

16/100 will do that

Havent yet had an instance where I need to go higher than 3 for minimum

[PIXELBOX_SRO]

here are some interesting comparisons..

difference between comp in PD and PS


difference between alpha PD vs PS


diffrence between alpha in PD vs VFB


from my tests, the alpha is coming way lighter in PS and is also full of noise and artifacts.
PD interpretation of alpha is a lot darker, such as if it had lower gamma, nicer and withtou artifacts.

anyway here is the result with the clean alpha



30 minutes rendere at full HD only for the ground plane :-/

[PIXELBOX_SRO]

16/100 will do that

Havent yet had an instance where I need to go higher than 3 for minimum

now i have the quality benchmark , i will try to tighten the AA some more

[Guest]

This has been an issue for us for some time, we end up just removing the noise as best we can in post and adding a blur to the shadow. It usually works fine for stills but for animation its a pain. We end up rendering the ground plane separately with higher settings as the rest of the scene is fine as is. It would be good to hear the correct workflow for a nice clean alpha that also doesn't take ages to render. We find disabling GI on the ground plane allows it to render much faster, so its just shadow from the HDRI. But the noise is still there :/