need help on buckburner and flickering, again

[Place]

Hi all,
I really need urgent help on this problem (it happens form time to time):
two machine collaborate with backburner to an animation; randomly it happen that some images
have slightly different light that becomes flicker once joined in video.

- All maps are saved in a Nas, the UHD Cache aswell
- Pc1 has BB manager and works as a server too
- Pc2 works like server
- The cache parameters are: "Try to load + append" and "save to file" (to nas)

so... my thoughts are that sometime  while a pc is trying to write the cache maybe is blocked by the other one that is writing it too
and this creates some  differences... is it possible?
And if it is possible, so what can be the workaround?
Or there is a better way to make it work flawlessly?

PROBLEM 2:
I added PC3 in the middle of the backburner job; same Max version (2016), same other stuff...
But each render of PC3 has more light in it.

Any idea?

Man

[TomG]

Load + Append with save from two different machines could be problematic as you mention (not really sure though). I would say the safest is to use the process to generate the UHD Cache in advance (just 1 pass, and have it do the load + append + save from one machine), then simply use Load and no save when rendering. You could also try just Calculate From Scratch and generate it each time (and you could try the 4K Cache if using a daily build).

Other thoughts, are you rendering to time, passes, or noise? Can you show an example of the flickering? Which version of Corona, which version of Max? Does the flickering go away if rendering using only one machine?

[Place]

Hi Tom,
thank you for your answer.

- We've got this problem randomly, with Max16 but with Max18 also.
- Corona version either was different, it happened with 5 and now with the latest daily build.
- Using noise limit with time cap.

Using the same machine doesn't show the problem.

Don't know if flickering is the right word, it is the overall light wich changes randomly.

Now the UHD Cache is loaded and written by all the pc partecipating to the rendering through backburner.

So can this be the problem? Better use a single cache, maybe generated by the fastest machine and the others just read it?

I attach an example of what I mean with flickering (sorry for escluding the rendered object)

[TomG]

TY for the extra info, and for the example! Yes, I'd call that flickering too, definitely the right description. I would definitely try one UHD Cache pregenerated then just read by all the machines. Generating it shouldn't take long as it doesn't need anything other than 1 pass (really it only needs to do the precalculation phase).

I'd also not use a noise limit AND time cap, just because some slower machines may hit the time cap and stop, while faster ones may do more passes and reach the noise limit, so some frames will end up different. I don't think that would cause this flickering, just that it could cause differences in noise, so is generally not a good idea on a network with mixed machines (even if all machines are identical, time is probably bad, as a host machine may need different time to load the scene than a remote machine), so I'd avoid time on network rendering and go with passes or noise as a limit.

Any sign that this is always the same machine that generates the brighter frames? Usual check there - same version of Max, same version of Corona, etc? If denoising is used, I'd say best to use Corona High Quality or Intel, not NVIDIA.

[Place]

The brighter frames are generated by different machines. There is the same version of Max and corona in all of them.
We always use Corona High Qeality for denoise.
Thank for the tips about noise/time cap.

When you talk about "pregenerated cache" do you mean to create it by putting a machine to render all the sequence with pass limit 1 only to generate it? I'm I getting it right?

[TomG]

Yes, though you don't need to render every frame, usually it's every "x number of frames" (every 3, 5, 10, depending on how fast the movement in the scene is). See https://coronarenderer.freshdesk.com/support/solutions/articles/5000515648-how-to-use-uhd-cache-for-animations-and-stills- for that.

And yes, would let one machine do that to generate the cache for the whole animation, and then use that cache on all machines with just a straight Load. If you can do a quick test first, that would be best, because I am not 100% convinced that the cache is the issue unfortunately - I definitely think it is the right thing to do, but, can't say it would solve this particular problem, so testing quickly first (smaller resolution, less frames so just a section of the animation, less passes so that the image is noisier but just clean enough to see if the flickering is still there, etc) might save the headache of waiting for everything to render out and still having the flickering.

[Place]

Wow, now I start to see the light!
I bet this is what will solve al my headache

I've read that page so many times, never really understending what I was reading...
It was there, trying to say me "Hey, stupid, I'm here! Why can't you see me?"

Tom, I really thank you!
I'll let you know if this will work.

[Place]

Hi Tom,
I can confirm you, everything now works smoothly.
Thank you!

Man

[TomG]

Great to hear, and you are welcome!

[momo85]

I have a flicker problem, I did this animation and as you can see on the horizon the water generates a strange effect how can I solve it ???

[TomG]

I'd start a new thread :) For one thing this is not the UHD Cache, but a totally different issue, which is why it would need to be under its own report. Thanks!

[momo85]

I'd start a new thread :) For one thing this is not the UHD Cache, but a totally different issue, which is why it would need to be under its own report. Thanks!

I ve open new thread thx TOM