Flickering foam!

[wsp]

Hi!

I have this foam flicker problem that I dont know how to get rid of?

Look at this animation.

http://www.kennetjohansson.se/temp/pipes.html

Look especially at the second half of the animation when the water has come flushing out of the pipes and
start to flood the scene. There is some crazy flickering in the foam there.
First i simulated the water mesh and rendered that out. it looked fine. Then whent on and resimulated with foam and splash.
Rendered again and the flickering started to appear. Everything is rendered in one go, water, foam and splash. No composition.
I used a domelight with a hdri, no global illumination. Vray 3.008, phoenix fd 2.2.
I used a physical camera with motionblur enabled. Adaptive image sampling min 2 max 6 color threshold 0,01. Global dmc at default values.
Tried to mess with some of the settings directly on foam and splash. Bounce, reflection cut of etc. I set reflection cutoff to 0,01. Could that be the problem?
Im a newbie on phoenix fd and any advise would be helpful.

[Ivaylo Katev]

hi,
the flickering foam is very common issue. in the most cases the cause is the shadows cast by the liquid, the bubbles are shadowed in one frame and lighted in the next frame, try to disable the "cast shadows" option of the simulator.
if the problem persist, try to render only the foam, and to add it in post (3d max has included simple compositing tool). even if the flickering is gone, the compositing is very useful, the foam render time and the liquid render time are significantly lower than the render time when rendering them both.

[wsp]

Ok thanks. You mean the checkbox disable liquid shadows right? I will try that.

[Ivaylo Katev]

actually no, the option disable liquid shadows can help only with implicit liquids, if you use mesh, that is the default case, you have to disable the option "cast shadows" of the object properties.

[wsp]

I use implicit surface mode in the rendering options so i did the right thing to use the checkbox disable liquid shadows?

[Ivaylo Katev]

if you use implicit, yes, the disable option should help

[wsp]

Ok after looking on the new frames rendered over night with the checkbox disable liquid shadows enabled I can see that the flickering is gone.
Great, thanks for the tip Ivaylo.