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Adaptive Domain causing 'twitches' in gas position when noise applied
Open, Confirmed, MediumPublic

Description

System Information
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.36

Blender Version
Broken: version: 2.81 (sub 3), branch: fluid-mantaflow (modified), commit date: 2019-08-27 23:26, hash: rB552149d8f537
Worked: (optional)

Short description of error
When I use adaptive domain, I have been noticing odd 'twitches' in the smoke's position once I've baked a noise pass.

Exact steps for others to reproduce the error
Bake the attached .blend and watch the sim playback, then bake the noise and watch the sim playback, you should see the 'twitches' I'm on about.
Here's my result- https://www.youtube.com/watch?v=-DPv9mUfQiI&feature=youtu.be

If you bake the sim without adaptive domain, it looks completely different, but there are no 'twitches' when the noise is added.
Here's my result of that- https://www.youtube.com/watch?v=Qda23EtCR2w&feature=youtu.be

I don't notice the problem every time I use adaptive domain, but I'd guess it happens to all sims, but maybe it's just not noticed if it's small enough.

Cheers!
Mark

Details

Type
Bug

Related Objects

Event Timeline

This task is not a duplicate of T70678

@Sebastián Barschkis (sebbas), wanna have a look if this issue is relevant as it is mentioning only the mantafluid branch.

Sebastián Barschkis (sebbas) lowered the priority of this task from Needs Triage by Developer to Confirmed, Medium.

Yes, this looks some data is missing during the noise bake. I.e. the noise bake job is not loading some data from the previous low res job. "Twitches" are usually missing velocities.

I am currently rewriting parts of the caching. That might resolve this issue. I'll come back to this once the refactored caching is finished.

As requested-

Typically: when I re-baked the old scene I couldn't see anything much wrong- until I removed the 2 Turbulence fields I was using to make the smoke look interesting, after which I was rewarded with an absolute corker of an example of the issue (TC 06:21 to 06:22)-

https://www.youtube.com/watch?v=OWt1Yp9IrRc&feature=youtu.be

You can also see something suspicious happening at TC 00:17 to 00:18 from the overhead camera.

Here's the scene file-

Something I have noticed, don't know if it's related but- adaptive domain doesn't seem to give a toss about the domain size & position once baked: i.e. in the attached scene the bottom of the domain goes way below where the domain was originally defined, and had it's scale applied, before baking.
Like so-
pre-bake

post-bake

Also I've noticed when baking the noise, there seem to be instances of 2-3 frames baking way faster than the rest (observed while watching the timeline play head whilst baking), I couldn't swear to it, but I think it's around when the twitches occur.
Additionally the twitch coincides with the time the wee box in the bottom corner of the domain moves in x,y,or z, which doesn't happen without adaptive domain being enabled.

Here's my current system info-
System Information
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 436.48

Blender Version
Broken: version: 2.81 (sub 12), branch: fluid-mantaflow, commit date: 2019-09-27 09:45, hash: rB114783000d0b

IMHO my issue is totally to do with adaptive domain, not with the domain being moved. I've never used a non-static domain so far (nice idea though, shall do in future!).

Cheers!
Mark