Author Topic: Water flickering with network rendering.  (Read 3185 times)

2019-09-03, 09:47:30

wilbertvandenbroek

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Hey guys,

I've been working on a short animation at work and I'm having a lot of trouble with fixing this flicker that happpens on a water sequence.
Attached is a short render. The setup is simple;

-sun and sky system for lighting with the sun only used for lighting (no reflection or refraction)
-one water plane
-visibility override with hdr clouds
-a few objects are visible in the render, I also tested without them (only water plane) and the problem still occurs
- see attached image for material properties of the water
-3ds max 2020.2 with corona 3 hf 2

We have got a render farm consisting of many different systems, i7, dell poweredge servers and older and new ryzen cpu's.
So far I can't see a pattern in which frame is flickering on which system.

Our render setup uses UHD cache with flickr free animation. We have moving objects so caching once won't work.
The material has an animated offset and phase in both noise and cellular maps.

Anybody got an idea? We are running into a deadline here :-(

Any help would be greatly appreciated.

2019-09-03, 09:58:57
Reply #1

snakebox

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The first thing that comes to mind is switch to PT / PT if you think the UHD has anything to do with it, and since you are doing a water sequence I suspect it's an out-door style shot anyway? in which case your get less benefit from UHD anyway, it should be quick to test at least, another thing I would try would be to turn off the bump map on your water, again just to confirm whether it comes from that or not.

I have personally had cases where a too fine bump would cause individual pixels to blow up and become really bright, then in an animation that would look like flickering. I'm not saying it's a solution, if you need the bump you need it, but if it works with it off, at least you know where you can tweak maybe.

2019-09-03, 10:10:37
Reply #2

dj_buckley

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i have a feeling it might be the HDR in the visibility override.  try without

2019-09-03, 10:36:06
Reply #3

wilbertvandenbroek

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Thanks guys I will try it immediatly.

2019-09-03, 10:44:39
Reply #4

rowmanns

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Hi,

Are you using DR or some other render manager?
If you are using DR, you can save the images which are sent from the DR slave so you will be able to see which machine(s) are causing the flickering.
You will just need to select the "[Debug] Save sent images" checkbox on the slave machines

Let me know if this helps.

Thanks,

Rowan
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2019-09-03, 11:34:57
Reply #5

wilbertvandenbroek

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Ok so far the results are the same:

- I've tested with uhd and pt/pt, no difference
- Turned of the visibility override. No difference

We are not rendering with DR

One odd thing I noticed is that the lighter patch of water that causes the flickering is happening only on the AMD ryzen systems. And to top it off the material of the yellow objects are also flickering now.

Attached a latest render, PT/UHD flickr free. Water bump in the displacement. Still problems.

So far no solution. Can different CPU's be a problem here?



2019-09-03, 12:31:10
Reply #6

rowmanns

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Hi,

It's a possibility that the different CPU architechtures could cause an issue like this. There has been a similar issue in the past with Corona Scatter and DR.

What software are you using to manage the rendering across the farm?

Thanks,

Rowan
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2019-09-03, 12:34:21
Reply #7

wilbertvandenbroek

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Just standard backburner 2019.

2019-09-03, 12:43:19
Reply #8

Place

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Hi,
do you use Backburner? And did you maybe set some post processing parameters like Filmic shadows?
Maybe you have to set those settings per camera instead of using VFB.
See here something similar that happened to me: https://forum.corona-renderer.com/index.php?topic=25637.msg153436#msg153436

2019-09-03, 12:51:10
Reply #9

wilbertvandenbroek

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Thanks for the tip, unfortunately we don't use any post processing options.

So far testing the following didn't resolve it:

- different water plane
- no sun and sky, only one directional
- rendering from perspective without camera animation

2019-09-03, 14:14:00
Reply #10

TomG

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Is it really Backburner causing the issue - if just one machine renders all the frames, does the flickering stop?

2019-09-03, 14:25:53
Reply #11

wilbertvandenbroek

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Well if I render it locally on my own workstation no problems occur. Every frame is the same.
However this is not a fix because my workstation alone can't render the entire sequence. It would take to long before the deadline.

2019-09-03, 14:36:53
Reply #12

TomG

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Yes, not suggested as a solution, just as a diagnostic, to make sure that it is in fact the network rendering that introduces this problem. That makes sure everyone is looking in the right place :) Could you render with just machines that have the same CPU architecture using backburner, to see if it is varying CPUs that are causing it? (I know these are slow tests to do, but they do narrow down the cause). Not sure if you have a group of machines that are all the same architecture or if each machine in the farm is very different.

2019-09-03, 14:41:19
Reply #13

TomG

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Also, with it pinned down to network renders, the usual first suggestions - is the same version of Corona and Max on every machine (including hotfixes and patches), are there are third party apps or shaders used (e.g. Bercon noise in the bump) and if so are those installed on every machine (and the same versions)?

2019-09-03, 15:00:09
Reply #14

wilbertvandenbroek

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So after a day of testing here are the results:

Rendering on a servergroup of Ryzens solved the water flickering. However the yellow objects still flicker and are caused by two workstations, one Ryzen 3900x and one 1700. See Waterbug_Ryzen in the attachement.

Rendering on all servers with a reflection glossiness of .85 instead of 1 sort of solved the flickering on the water shader. (see attached Waterbug_V02) The water looks slightly less appealing but at this point I'm happy with this result.

Still no solution for the flickering in the yellow objects.

All our systems run the same versions etc. no difference there.