Yacht Wake Foam tests

[waaazoo]

Hi guys,

Here is a new test with a 62 meter yacht at 13 knots. Still work on that to do, but it's a good start I think.
I used IR and LC but there is still some flickering.

https://vimeo.com/260926059

I will update as soon as possible.

cheers

[Paul Oblomov]

Patterns feels off to me

[waaazoo]

Patterns feels off to me

Hi Paul,

Too big, too small ? what do you think?

[Svetlin.Nikolov]

Hmmm, there are some bucket artifacts. Was the scene rendered with DR on machines with different number of threads?

[waaazoo]

Hmmm, there are some bucket artifacts. Was the scene rendered with DR on machines with different number of threads?

yes, DR with very (VERY) different machines

[waaazoo]

Hi guys,

Just to confirm, rendering with DR creates bucket artifacts as seen in the first video. When rendering without DR these bucket artifacts disappear.

https://vimeo.com/261448773

password: phoenix_artifacts

second problem: I have now artifacts at the end of the Grid. Also end of grid is clearly noticeable. How can I resolve this?

[Svetlin.Nikolov]

Hey, could this be caused by too low Outside Life?

I'll try to fix the buckets issue as soon as possible.

[waaazoo]

Hey, could this be caused by too low Outside Life?

I'll try to fix the buckets issue as soon as possible.

Outside life is at 25 Svetlin. Is this too low? I think it's already quite big, no?

[Svetlin.Nikolov]

You can check this easily - enable the foam particles in the viewport preview and zoom in on the border area with detail reduction = 0. If foam particles die immediately when exiting the simulator, then you need more outside life. Remember that the outside life means the total time since birth of the particle above which it would die outside the simulator, not the time since it went out.

Cheers!

[waaazoo]

You can check this easily - enable the foam particles in the viewport preview and zoom in on the border area with detail reduction = 0. If foam particles die immediately when exiting the simulator, then you need more outside life. Remember that the outside life means the total time since birth of the particle above which it would die outside the simulator, not the time since it went out.

Cheers!

it doesn't look like the outside life is too short

https://vimeo.com/261608562

password: phoenix_artifacts

[Svetlin.Nikolov]

Hey,

From such big distance, the preview does not really provide any useful information since in the particle shader the points usually have alpha of about 0.1-0.15, but they will appear much denser in the preview where they are always opaque. Let's approach this in a different way.

Here are a few scenarios I have encountered while dealing with such scenes so far. I hope they can guide you on what to look for and how to test it. It's very important to be able to use the preview and rendering to catch such problems yourself so you can work quickly and effectively:
- The particles may die when they exit the simulator. If all particles die, then the Age channel is missing. If only some of them die, the only possible reason would be too low Outside Life. You can figure out if this is a credible explanation if there's at least 25 seconds between the moment when a particle is born from the front of the vessel to the moment it exits the back end of the grid - if the time is enough, you can prove it by zooming in the preview with reduction disabled and tracing individual particles at the border. If particles disappear, then you need more Outside Life.
- The particles may not be dying at the border, but might be stacking at the walls. How to verify this - again, use the particle preview and zoom in well enough so you can see it. If this is the case, then you have to find what stops the particles from exiting the simulator. Maybe the ocean level is too low or high, it's good to check the velocity preview as well.
- The particles may simply render differently. If the ocean level outside and inside the sim don't match, then its possible that some foam particles which are on the water surface inside the sim suddenly appear underwater when they cross the border. Then they will be rendered tinted by the water's fog color and it would look like there are more particles inside the simulator than outside it, but in fact some particles will just be under the surface. The easiest way to test this would be again the preview, or otherwise you can just make the simulator not renderable, render just the particles and check their alpha. If there is something clearly going on at the border, then it's one of the two scenarios above.

Just my 5 cents - if I wanted to have absolutely no issues with the trail, I would just make the simulator long enough to fit it. Outside the container there is no fluid simulation. Only a few of the processes that happen inside can happen outside, so you are depending on those that are missing, you'll have issues with the trail.
Cheers

[waaazoo]

Svetlin,

Thank you very much for this exhaustive explanation. I will check again what happens and report here.

[Svetlin.Nikolov]

Hey, so the flicker should be fixed in today's nightly ID 28170

Cheers!

[waaazoo]

Hey, so the flicker should be fixed in today's nightly ID 28170

Cheers!

Thanks Svetlin for the note. do you speak about the DR flickering or something else ?
Concerning the lasts posts, I discovered that when I render the foam alone (without the sea mesh), everything is pretty smooth. I will post something later.

thanks again for your support

[Svetlin.Nikolov]

Hey - I mean the bucket flicker.

If everything is okay when rendering just the foam, then it's something about the interaction with the liquid mesh. Could be that in the particle shader you've chosen to render only the subgroup above the liquid, or you need to enable 'disable liquid shadows', or the fog color of the liquid material is too strong, or the liquid volume is not a closed geometry and the V-Ray fog color can't work this way so all foam under the surface is affected heavily by the fog color...