Why do I have this gap in my smoke?

[hunter_williams]

The emitter is a disc (circled in red) and is parented to the missile.

[StufishIT]

Personally I would simply make the 'nozzle' 'invisible to Phoenix and just move the emitter up a bit into the rocket body, and also try playing with the scale of the simulation - by factors of 10 at least! (Perhaps at the moment your grid is so very low res, that the smoke is simply moving too fast through it that close to the emitter.)

[hunter_williams]

Why would I increase the Grid scale past 1? I'm not trying to simulate something in slow motion.

[hunter_williams]

Another thing I noticed is that the disc that has an nParticle emitting downward seems to shoot upward as well:


It's set to surface:

And the fire/smoke is set to surface force:

[hunter_williams]

One more thing, I don't think motion blur is on the smoke, I have a velocity channel but it's at 0.00:

Only thing I can think of is that my missile isn't moving fast enough to generate velocity.

Any ideas?

[Svetlin.Nikolov]

Hey, have you tried caching the nParticles before simulation? Does it make any difference in the gap between the emitter and the fluid? Or another thing to try - the Forward Simulation option in the Simulation rollout - please try it with cached nParticles and without caching the nParticles too.

As for the velocity - what you see is the range - it says the velocity goes from 0 to 2253, which looks quite alright. How does your velocity viewport preview look?


You could also turn off the GPU Shade Preview a couple of rollouts further down, and also turn off the Temperature, Smoke and Fuel checkboxes above to get a clearer view.

Cheers!

[hunter_williams]

Hey Svetlin,

So I cached the particles and then ran the simulation. The result was no simulation (I seem to remember in a previous thread you mentioned to turn off caching for nParticles, otherwise they won't simulate).

Here is the result of caching the nParticles, then turning off caching and doing the simulation (there is still a little gap):



Next, I tried caching then turning off caching and running the simulation with Forward Simulation turned on. The result was not desirable:




As for the velocity, I checked the preview and it's on and a few test renders seem to confirm that it's working.


Here is a stripped out version of the scene for you guys to check out:

https://drive.google.com/file/d/1isG...usp=sharing

[georgi.zhekov]

Thanks a lot for the scene - will check what is going on and will get back to you when we know more.

[Svetlin.Nikolov]

Hm, I already forgot the exact situation, but I think it was the timeline caching that broke nParticles, not the nCache I was referring to.

Thank you for the scene, will check it and hope we will be able to get back to you in a couple of days.

Cheers!

[georgi.zhekov]

Hey,

Just checked the scene but seems fine over here, using the latest Phoenix 5.10 build from the chaos website and Maya 2023.

Does the gap show from the start? I simmed the first 80 frames or so and looked good.

Looks like the simulator you have gets fairly large, could it be that the gap shows only in later frames? If this is the case, maybe you run out of RAM and the grid can't expand more. You can check the Phoenix log (usually located at C:\ChaosPhoenix) - if you run out of RAM there should be an error about it.

Here is how it looks on my side.

[hunter_williams]

I just tried the test scene that I sent you and now I'm getting similar results. I wonder if it's because I stripped out all the other geometry and sims out of the scene?

[georgi.zhekov]

Could be, if you can send over the scene where the problem is reproducible we can try to debug it and check what is going on there.

If sending the scene is not an option, you can try to start removing things one by one and check when it starts working correctly.

[hunter_williams]

Here is the updated scene:

https://drive.google.com/file/d/1isG...usp=share_link

I'm also noticing some flickering here:


Here is a video that shows it, please don't say I need to sim again with a higher grid resolution

https://drive.google.com/file/d/1sjf...usp=share_link

I'm using Maya 2022.2, Phoenix 5.10.00, Vray 6.00.03

[slavina.nikolova]

Hey,

Thanks for the scene! It looks like the nParticle emission is animated and after frame 120 no particles are generated - therefore there is no emitter in the scene to generate the fluids and that's why you have the gap.
As for the flickering, you might try increasing the Grid Resolution a bit and simulate again. You might also try increasing the number of nParticles.

Hope this helps!

[Svetlin.Nikolov]

Yup, might also help the flickering if there are more nParticles, but they emit less fluid, so the edges of the fluid will be less solid.