foam flickering - beer animation

[jgreen3895]

Been running some tests with the suggestions of disabling light cache, turning off highlights, and plugging the HDRI texture into the environment slot. Were any other changes made to the scene settings? Did you adjust the mode from bubbles to cellular, change the reflection cut off, etc.?

Also, any suggestions for lowering the rendering times because as you said, disabling light cache and using the HDRI as a texture really slows things down to the point that it just takes too long to render. Were talking about an exponential increase in render time. You mentioned changing the lighting. By that did you mean not using a dome light on the foam or just not using the particular HDRI texture that's currently being used? I assume the former is what you meant because why would one HDRI work differently from another in this scenario?

[georgi.zhekov]

Just set the highlight strength to 0 - this should be enough.

Unfortunately without the Light Cache - there is nothing much we can do in order to speed up the renders.

My guess is that there are a few bright spots in the HDRI texture (the lights) that are causing the issue. I tried with a texture that has only one bright spot (an outdoor scene with a sun) and it seems to render fine even with the Light Cache turned on, just using the HDRI in the Environment slot of the Particle shader and the highlights disabled.

The other thing you can do is switch the Dome light and use V-Ray Rect Light - this seems to render without flicker as well.

[jgreen3895]

I'll give those suggestions a try. Thanks again!

[jgreen3895]

Hello Georgi,

Would it be possible for you to send over the scene file with the settings that seem to be working for you along with the HDRI texture you said you tried? I've tried several HDRI textures and I've tried just using vray rectangular lights, but regardless of what I do the foam still seems to flicker. This would be extremely appreciated. Please let me know.

Thanks!

[georgi.zhekov]

Hey,
In order to test your scene I had the Count multiplier set to a really low value so I could render only a few particles fast and check what is going on. Rendering the scene in this way - there is no flicker with the suggestions I made.
Unfortunately when I rendered it with all of the particles I can't get rid of the flicker as well - looks like a bug and it's something that we need to fix on our side. For now - rendering without light cache seems to be the only way.
I will update the thread when we have something regarding this.

[jgreen3895]

Hey,

I've had the same results on my end. The flickering seems to occur when there are really dense areas of particles. Lowering the count reduces the flickering, but obviously that isn't an option. Rendering without Light Cache doesn't appear to be a practical option either. If this problem is a bug with Phoenix FD 3.0 like you say, I guess there is nothing I can do now except wait for a fix. If you or anyone else here has any other suggestions please don't hesitate to let me know. Otherwise, please keep me posted on any potential fixes for this bug.

By the way, the reason I choose to test/learn phoenix fd with this type of an animation is because of the following youtube video. There aren't that many tutorials out there for phoenix fd that go into as much detail and this one seemed the most practical in terms of the type of work I do (product renderings). For whatever reason though, the video doesn't seem to have any issues with foam flickering.

https://www.youtube.com/watch?v=4GpSWx-DX_U&t=41s


Thanks.

[Svetlin.Nikolov]

Hey,

It uses simpler lights, most likely that is the reason.

I still haven't had a chance to look at the scene myself as I'm working on several other outstanding tasks, but this is very important and I hope I can be on it by the end of the week.

Cheers!

[jgreen3895]

Hey Svetin,

Appreciate your continued input. Thank you.

[Svetlin.Nikolov]

Hey, just an update - the last few days I've been working on these issues and they are rather nasty, but hopefully tomorrow or the day after you'll be able to try a new nightly with fixes for both the dome light bubble flicker and for the distributed rendering flicker. I will ping you when there's progress.

Cheers!

[jgreen3895]

Hello Svetlin,

Thank you for the update. I really appreciate all the time and effort you've put in to help solve this issue. I look forward to seeing if these fixes will work.

Thanks!

[Svetlin.Nikolov]

Hey,

We're half way there - just coming out are builds with ID 28170 where there shouldn't be any bucket differences and flicker in frames with bubbles or splashes rendered on different number of threads or different machines.

As a side effect, bubble and splash mode rendering with the Phoenix Light Cache enabled is now about twice faster.

Hopefully this won't break everything and I'm on to checking how to achieve more stable highlights with a dome light over the bubbles in animation...

Cheers!

[jgreen3895]

Hey,

Thank you for the update. Please continue to keep me posted and let me know when new builds are ready to download and test out.

Thanks.

[jgreen3895]

Hey Guys,

Just wanted to check in to see if any new developments that could perhaps solve these issues has been made. Last comments had to do with new builds. What's the status on those? No rush.

Thanks!

[Svetlin.Nikolov]

Hey,

Sounds like you probably don't know about nightly builds? Please check here - https://forums.chaosgroup.com/forum/...nightly-builds

I just ran some more tests with small number of bubbles rendered up close in order to be able to see how the highlights from the dome light change over them and a lower light cache speedup helps get a smooth animation without flickering, while speedup of 0.99 would cause much less rays to contribute to the specular highlights on bubbles and this causes them to flicker in animation.

One final problem I am looking at right now is that there is still difference when rendering on a different number of threads when Glass Geometry is enabled.

Please check a latest nightly and see how it does.

Cheers!

[jgreen3895]

Hello Svetlin,

Thanks for telling me how to get the nightly builds. I did not realize how that worked. I updated to version 3.10.01 Nightly, Build ID: 2018041628196. I definitely notice some performance improvements. Unfortunately, I still can't seem to get rid of the flickering. I've tried rendering frames 435-450 using multiple settings on light cache speed up and flickering was still occurring. I also played with bounces and reflection cut off, but still couldn't seem to get a flicker-free result. You said you've had some good results on your end. Could you share the settings you've used on the foam? Both the general settings and the Cellular/Bubbles/Splash rollout settings please.