Volumetric artefacts with arealights/foglights

[rcm_andy]

Hello,

in severel recent jobs i wasn´t able to render artefact free volumetrics with meshlights/arealights (see attachment). It seems at the boundaries between the arelight/meshlight those splootches are happening. Only spotlights are "splootches" free so far.

If i attach a "V-ray fluid shading quality" properties to the fluid node and set the VolumeShader to "VrayEnvirnomentFog" it works at the cost of heavy rendertimes. I tweaked every parameter for PhoenixFD Mode like Stepsize, Maxsteps, Subdivs whatever or the probalistic settings in the rendering overrides without success. Also increasing the maya fluid resolution to insane values didnt help. This relates to maya fluid containers as well as for vrayVolumeGrids with vdb.

Please find attached two videos, one PhoenixFD Shader and for comparison VrayEnvironmentFog and a maya file.

Thanks,
Andy

[georgi.zhekov]

Hey,

When using the PhoenixFD attributes can you try disabling the Volume Light Cache option. It generally speeds up rendering but sometimes it might produce artifacts.
You can find more about it here - https://docs.chaosgroup.com/display/VMAYA/Smoke+Color

Cheers!

[rcm_andy]

Hi Georgi,

i did without sucess, plaese have a look

[georgi.zhekov]

Hmm, then we'll need a bit more info.

Which version of V-Ray and Maya are you using? Are you on Win or Linux?

[rcm_andy]

Windows
Maya 2019.3

V-Ray: V-Ray Next for Maya, update 2.2 version 4.30.02
V-Ray: V-Ray core version is 4.30.03

[georgi.zhekov]

Hey,

Unfortunately we can't seem to reproduce it in here.

What we do is to open your scene, add the Phoenix attributes to the fluid containter and disable the Volume Light Cache.

Since we tested using the same software versions and it works on our side, it could be the hardware that it is causing the difference.

What hardware are using?

Thanks!

[rcm_andy]

Hi Georgi,

could you please post a screenshot of your phoenixfd attributes ?

We have only Intel Xeon Nodes so far

[georgi.zhekov]

This is how it looks. Everythying is at default, just the Volume Light cache is turned off.

Do you have any idea what kind of Xeons?

Thanks!

[rcm_andy]

E5 2670 V1
E5 2697 V4

Could you provide me your testrender for comparisson ?

Thanks!

[waaazoo]

I'm testing it here with Maya 2019.3.1, Vray Next (V4.30.02) and PhoenixFD 4.30.01 on threadrippers.
I'll post the mp4 when I have the result.

[rcm_andy]

Wow, thanks very much!

[waaazoo]

here is the result over 50 frames. I don't see artifacts, except in the middle maybe.

fog_test01.zip

[georgi.zhekov]

Here is how it looks on our side.

https://drive.google.com/file/d/1Jp-...eHhuO6J_p/view

[rcm_andy]

Many thanks for your efforts! Do you have any idea what could be the problem ?

[tashko.zashev]

Since the issue can't be reproduced in our tests, we can try to troubleshoot it further in remote session, Is that possible ? If yes, please use the contact form from our web site to create a support ticket and add a link to this forum thread. Then we will use the ticket to organize the meeting.