Foam point mode issue

[waaazoo]

Hi,

I have an issue I don't seem to have experienced before.
When I render the foam particles in point mode, I have some strange dark/black areas coming up. It seems to happen in areas where there is a high density of particles, and it doesn't occur when I render the foam in bubbles or cellular.

Foam points

Foam bubbles

Foam cellular

Foam points zoomed


And when you zoom in, the issue seems to disappear. I don't think I ever experienced such a problem with previous versions of Vray/Phoenix

Maya 2019.3.1, Vray V6.00.02, PhoenixFD 5.01.00

I tried, in the phoenix shader, to play with Motion Blur, Scattering, Volume Light cache, size addend, vertical offset. Nothing helps. The only thing is that when I reduce the count multiplier, it seems to damp the issue.
I'm still testing.

[waaazoo]

oh, and it's not that the particles are killed or dissapear. As you can see in the alpha, there are particles, but they are dark.

[waaazoo]

ok, something is broken or definitely different with shadow strength.

Without shadow strength, the problem is gone, but it looks like S[censored]t

[Svetlin.Nikolov]

Oh, huh, could you send this file along with one cache so we can see what's up? This doesn't look right at all.

[waaazoo]

Oh, huh, could you send this file along with one cache so we can see what's up? This doesn't look right at all.

Thanks, I will try to put something together and send it to support.

[waaazoo]

Hi Svetlin,

I sent a stripped down project to the support (Your ticket number is: 65065)
There is an AUR on frame 500 which is the one I tested.

I'm curious to see what you can find.

cheers

[Svetlin.Nikolov]

Sweet, got it! Thank you! We will ping you when we know more...

[waaazoo]

great !
If it can help: I was also trying out to export particle RGB on this simulation. In the Phoenix particle shader, it is not used, because I couldn't find any good way to use it. But maybe it has something to do with it.

[Svetlin.Nikolov]

Ah, okay, we'll see! We managed to reproduce the problem here and now Slavina is simplifying it...

[waaazoo]

Ah, okay, we'll see! We managed to reproduce the problem here and now Slavina is simplifying it...

great, thanks a lot!

[slavina.nikolova]

Hey,

While we're checking the scene, you can try the following steps as a workaround:

- set the Scattering to Approximate+Shadows;
- keep the Volume Light Cache enabled;
- decrease the Point Radius (I tried with 1.5);
- decrease the Shadow Strength (I tried with 0.6).


Hope this helps!

[waaazoo]

Hey,

While we're checking the scene, you can try the following steps as a workaround:

- set the Scattering to Approximate+Shadows;
- keep the Volume Light Cache enabled;
- decrease the Point Radius (I tried with 1.5);
- decrease the Shadow Strength (I tried with 0.6).


Hope this helps!

Thank you Slavina. That seems to do the job for now!

[waaazoo]

Thank you Slavina. That seems to do the job for now!

Except that with Scattering the foam becomes very bright. That's why I don't use it anymore. We could need a scattering multiplicator

[waaazoo]

Hi,

Any news on this issue ?

best,

Olivier

[Svetlin.Nikolov]

No, will try to have a look at it next week...

Cheers!