Calm/Slow Ocean Sim producing strange flickering between frames (looks different)

[ice_creative]

We are trying to do an in-house animation of a calm or slow moving ocean with a 3d logo half submerged in it - I have noticed that using Phoenix FD 3.12.00 (Oct 29 2018 ) for 3ds max with the attached scene seems to produce strange flickering and differences between frames on a backburner render on our machines here.

I must stress that this setup renders totally fine if we set the ocean simulation to default by creating a new one, simulating it then rendering it- but we wanted to make the ocean more calm so I changed the 'Rate of change' value on the PhoenixFDOceanTex from the default 0.1 to 0.03 or 0.02 then doing a fresh simulation and rendering seems to make some of the frames look slightly different from each other (enough to really spoil the animation)

Has anyone else noticed this or are any of your team able to have a quick look into this?

The only thing we are doing is changing the PhoenixFDOceanTex from the default 0.1 to 0.03 or 0.02. I feel like we may have found some odd bug that nobody else has since I've trawled through the forums for similar cases.

[ice_creative]

Have attached a video example - https://vimeo.com/299188722

[Svetlin.Nikolov]

Hey,

Are you rendering the entire sequence on one machine or on many? Does it happen if you render locally as well, or only when you render on remote machines?

Cheers!

[ice_creative]

Hey,

Are you rendering the entire sequence on one machine or on many? Does it happen if you render locally as well, or only when you render on remote machines?

Cheers!

I will attempt a render on one machine today to see, do take a look at the video above (the vimeo link definitely works)

Thanks for responding so soon

[ice_creative]

Hey,

Are you rendering the entire sequence on one machine or on many? Does it happen if you render locally as well, or only when you render on remote machines?

Cheers!

Rendered on one machine here over backburner, the entire cache folder was wiped before I resimulated to ensure no frames weren't being saved over, all settings for the ocean are at default except for the OceanTex Rate of change being at 0.02 instead of the default 0.1

I can also provide a 3ds max 2019 scene which recreates this issue

https://vimeo.com/299209144

[georgi.zhekov]

Hello,

Can you pack a few of the problematic caches along with the scene so we can check it out? I can't seem to reproduce the issue in here.

Thank you,

[ice_creative]

Hello,

Can you pack a few of the problematic caches along with the scene so we can check it out? I can't seem to reproduce the issue in here.

Thank you,

Hi Georgi

Find the files attached here, the cache storage quality is set to 15 (1 above default) as for this test I wanted to see if the quality had any effect but it didn't resolve the issue - the only thing I can think is that I am storing the frames on our local office windows server and they are being saved there during the simulation - this is so that all the backburner rendering machines can all see the phoenix frames.

I will try calculating locally on one machine to see if there is any difference but it looks like the frames are saving just fine individually but the simulation is behaving oddly, I will have to report back on that after testing it out, hopefully the cache files with this zip from our server stored phoenix cache reveal something

https://www.dropbox.com/s/jzz06dij8f...cenes.zip?dl=0

Files here in a zip, included 80 or so of the simulation frames

[ice_creative]

I have just finished testing out simulating the same scene locally on a machine here, then rendering on that same machine - the ocean waves are still behaving similarly with weird flickering as if a smaller wave is occasionally shooting underneath the simulation and jolting it. The simulation is fine if I set the PhoenixFDOceanTex back to the default 0.1.

Am happy to provide any more reference material for your investigation, I'm a little stumped for what to do with the animation now as I just wanted a calm sea simulation. Hopefully your team can find something in my provided cache? I wouldn't mind being sent the perfectly fine cache that you guys produced when checking this out earlier as you couldn't reproduce the behaviour!

[georgi.zhekov]

Hey,

So I have checked the scene and the flickering happens because of the simulation itself.
You're using quite low grid resolution and there are some waves that are hitting the logo and then reflecting back and this looks like flickering because the water is moving faster than the displacement. The good thing is that you have a few options to solve that.

The easiest option is to turn on the Pure Ocean mode from the Simulator's Rendering rollout. It does not need loaded caches and if there are any, it ignores their content, so no simulation details will show. Using this option though won't create waves (foam,splashes, mist won't be created as well) from the movement of the logo, but if you don't need it to interact with the liquid - this is the best solution.

The second option is to add a bit more resolution to your sim and add a few more steps per frame.This should make the water behave a bit more stable.
Still if the Ocean Texture used for the displacement moves so slowly you might need to slowdown the liquid as well in order to avoid the issue you're having. You can do this by lowering the Play Speed in the Input rollout of the Simulator. You can find more about it here - https://docs.chaosgroup.com/display/...meBendControls Note that lowering the Play Speed might not produce great results if you set it too low. So you will need to balance this out along with the animation of the objects in the scene.

Cheers,

[ice_creative]

Hey,

So I have checked the scene and the flickering happens because of the simulation itself.
You're using quite low grid resolution and there are some waves that are hitting the logo and then reflecting back and this looks like flickering because the water is moving faster than the displacement. The good thing is that you have a few options to solve that.

The easiest option is to turn on the Pure Ocean mode from the Simulator's Rendering rollout. It does not need loaded caches and if there are any, it ignores their content, so no simulation details will show. Using this option though won't create waves (foam,splashes, mist won't be created as well) from the movement of the logo, but if you don't need it to interact with the liquid - this is the best solution.

The second option is to add a bit more resolution to your sim and add a few more steps per frame.This should make the water behave a bit more stable.
Still if the Ocean Texture used for the displacement moves so slowly you might need to slowdown the liquid as well in order to avoid the issue you're having. You can do this by lowering the Play Speed in the Input rollout of the Simulator. You can find more about it here - https://docs.chaosgroup.com/display/...meBendControls Note that lowering the Play Speed might not produce great results if you set it too low. So you will need to balance this out along with the animation of the objects in the scene.

Cheers,

Great suggestions - since the logo is static, Pure Ocean is the best fit (wish I thought of that in the first place - so many options on the simulator rollout that I easily missed it!)

As for the steps per frame, that makes sense now that what we were observing was the reflected waves, as the PhoenixFDOceanTex Rate of Change would only affect the velocity of the default waves and not any simulation-caused waves. This is probably a very specific case anyway but I hope this thread being here will help anyone else who tried to do the same thing and finds the same result.

** It would be really helpful to have a note on the PhoenixFDOceanTex Rate of Change description in the PhoenixFD docs that it only affects the velocity of the default waves and any simulated waves will behave independently of it/could cause undesired behaviour, but like I said this is probably a specific case

We are rendering with Pure Ocean on now and it looks perfect for our needs. Will try messing about with the Play Speed at some point but I've spent a fair bit of time re simulating when I actually just needed to use Pure Ocean!

Thanks so much for the help,
Rob