Smoke popping when there is more sphere lights

[zjie]

Hi,

We were doing some renderings and we found out that the smoke appears to be splotchy when more sphere lights were added.

I did some test of which the smoke appears fine when there is only one row of sphere lights : https://drive.google.com/open?id=1oQ...Kkhff4rJTgY9Ic

However, when rendered with 3 rows of sphere lights, it became splotchy and pop every few frames : https://drive.google.com/open?id=1_Q...gRE6sVKjRsQM9D

We couldn't figure out why is it happening, we are using maya 2018.2, phoenixfd 3.05.00, vray 3.60.03

The scene and cache file is here: https://drive.google.com/open?id=1tO...7jdWRpfoO4TODy

[Svetlin.Nikolov]

Yup, if you are getting grid artifacts, this is the Phoenix Light Cache. Try reducing the light cache speedup or if this doesn't help, turn it off completely.

Cheers!

[zjie]

Hi Svetlin, I have set the light cache to 0 but still doesn't help, turning it off will result in render time increase. But do you know what is causing the artifacts? Could it be there is too much lights, intensity too strong?

[Svetlin.Nikolov]

Yup, too many lights. The Phoenix light cache is a big time saver and this is why it's on by default, but if you are getting such artifacts, then you have to fallback to the default render speed.

[zjie]

Hi Svetlin, I found out that one scene could only hold a maximum of 5 sphere lights, any number greater than that, artifacts will appear, even if the other lights are disable, intensity 0, and affecting nothing.

[Svetlin.Nikolov]

This is more of a V-Ray question I'm afraid. I don't think there is an exact formula for it as it would depend on the intensity and size of the lights and the opacity, resolution and shape of the smoke...

[zjie]

Hi Svetlin,

It doesn't make sense, the other lights were all 0 intensity and not affecting anything, but they would still cause the artifacts, but once I have deleted those 0 intensity lights, the artifacts are gone. Hiding the lights from the scene also doesn't work.

[Svetlin.Nikolov]

Hey,

How lights are managed is up to V-Ray - Phoenix doesn't have anything to do with whether a light is on or off and how it affects illumination.

Cheers!

[Svetlin.Nikolov]

if possible, please send a scene over which helps reproduce this exact issue and I'll take care for it to reach the guys.

[zjie]

Hi Sveltin,

Please find the file here: https://drive.google.com/open?id=1aq...wXQ-vIi8DFuf1t

I have also attached an explanation image, hope that it is straight forward.

Really appreciate for your help, thanks again!

[Svetlin.Nikolov]

Hey, thanks!

Meanwhile you can turn the Phoenix Light Cache off for rendering.

Cheers!