Smoke - Light Link Flickering

[pipe_mm]

Hello,
I am testing this scene. Cup blasting through snow.
The sim works fine, but there seems to be a problem with the light linking between the main light (rect, directional) and the smoke.
For some frames the light is linked, others appear dark.

https://my.green-cloud.at/index.php/s/LNkG9C87mWTYCtJ

The GI mode is already set to Brute Force / Brute Force

The problem happens inside maya VFB, as well when rendered over deadline (3 machines)
Would be glad to know if this is a known issue and hopefully a quick fix.
Thanks
Martin

[kostadin.petkov]

Hello,

Recently we found and fixed a couple of issues regarding Light Linking in Volumetric render mode.
You will need to upgrade Phoenix FD (to the latest nightly) and V-Ray for Maya with the latest Release.
If after upgrading V-Ray and Phoenix the issue still persists,
you can try rendering in "Volumetric Geometry" render mode, while sending us your scene for debugging so we can find what the issue is.

Hope that helps,

Best,
Kostadin

[pipe_mm]

Hello Kostadin
how do I get the latest Phoenix nightly.
through the download area I can just see Phoenix 4.00.00 for Maya 2018 Next
Very much curious if this solves our problem
Thanks
Martin

[Svetlin.Nikolov]

Hey, make sure to check the sticky topic in this forum about nightlies

[pipe_mm]

Hello Niklov
I downloaded and installed the latest Vray & Phoenix
Still the problem occurs.
Switching to Volumentric Geometry does solve the problem, but it renders slower and the look is more solid.
So I packed the scene for you here.
Data and the HDRI image included
https://my.green-cloud.at/index.php/s/PgbNJF652yxRegM

It would be great if you could take a look at the scene
Martin

btw: totaly other question. I cannot find the Vray Next Edu in the download section. Thnx

[kostadin.petkov]

Thank you for sharing your scene!

I feel like we are talking for different Phoenix and V-Ray builds
Just to be sure here are the builds that I'm taking about:

V-Ray - https://nightlies.chaosgroup.com/mai...e_4.3/20200204
Phoenix FD - https://nightlies.chaosgroup.com/mai...ghtly/20200204

Could you confirm that these are your builds, and if not could you give them a try?

[pipe_mm]

I installed the latest builds now.
still some frames lose the light link in "Volumetric"
it works fine with "Volumetric Geometry"

"Volumetric Geometry" take much longer rendertimes compared to "Volumetric".
thnx
Martin

[kostadin.petkov]

Thank you for verifying the builds!

it is expected to have "Volumetric Geometry" render slower, as it is a bit more flexible (enabling us to achieve more advanced effects at the cost of speed).
Meanwhile we will take a look at your scene!

[pipe_mm]

pretty happy with Volumetric Geo right now
thnx for your support

[pipe_mm]

Hello

just as I was feeling save with the "Volumetric Geometry" solution another porblem popped up.
As you can see there seems to be a problem on tranparent backgrounds.
Acutally he ground plane is getting some heavy alpha mask artifats in "Volumetric Geometry" mode.
I couldn´t find a setting/button within the rendering settings of the Phoenix Sim Node to solve this issue.
Going back to "Volumetric" does come up with a solid alpha.

Still I cant use "Volumetric", cause here I get a light link flickering.

Please let me know, did I do something wrong?
Should I rebuild the scene from scratch?
Is this a known issue or am I messinig?
Will I be able to meet my deadline in two days?

Thanks
Martin

[pipe_mm]

in "Volumetric Geometry" changing the Smoke Opacity from "Simple Smoke" to "Smoke" gives me a stable alpha in those floor connection areas.
hmm - tricky pony

[Svetlin.Nikolov]

Hey,

Can you double check in your Maya log after rendering if you are getting a warning that sounds like:

// Warning: V-Ray : [PhoenixSimPlugin] To get better results with Volumetric Geometry mode rendering, you may need to increase the Max transparency levels of V-Ray to about 134. //

If you indeed have this, follow the advice and it should resolve the issues you are getting

Cheers!

[pipe_mm]

thank you Svetlin - now it all works perfectly fine

[pipe_mm]

Hello, I have one question that is not concerning the smoke but the liquid I am using in the same scene.
There are a view drops outside my glas. The sim is perfect, so I dont want to resimulate it. Is there techique how to delete those stray away voxels/mesh?
thanks
Martin

[Svetlin.Nikolov]

Sure, use the Render Cutter to remove geometry at render time - https://docs.chaosgroup.com/display/PHX4MAYA/Rendering