The bug UE-172069 highlights that in Movie Render Queue, physics seem to generate a new seed for every temporal AA (goes crazy on every frame). A clue for the devs as to what might be causing this… If you set your Motion Blur to 1.0, the physics become normal again. Anything below 1.0 and the physics will be different every frame. So something with motion blur is causing issues with temporal AA and cloth and hair physics. I wasn’t sure where to mention this but I’m hoping it helps as this bug has been around for awhile now.
Hello!
is normal because is temporal just deactivate it
set a proper anti aliasing!
It’s a bug that has been fixed in 5.2.
Did you try my solution? because I’m sure even so, the quality is better
Temporal samples is what we want, not video game AA. Temporal will sample the frames around the rendered frame and give you a much more accurate motion blur and anti-aliasing. This is a bug. I’ve talked with a developer who says it has been fixed in 5.2 (although I have not tested it yet).
I keep hearing this has been fixed in 5.2, but that remains to be seen for me. I even saw the bug report online, but I think it was primarily aimed at cloth. They said it was fixed, but its not. Cloth still doesn’t seem to behave correctly when I use Temporal AA on MRQ. Not only that, ANYTHING with physics behaves unexpectedly. Hair, Cloth, Niagara Particles, you name it.
For a shot, I have a subtle Niagara cloud being emitted that floats, but needs to inherit velocity from character movement. Looks fine in engine and when simulating. But once you turn on Temporal AA in MRQ, its like the inherited velocity is being being insanely beefed up at like 10x. And the particle is literally flying out of the scene.
The developers on the bug report mentioned its because time dilation is bugged when using Temporal AA in MRQ? But they mainly tried to address it with Cloth. But why only cloth when many other physics related features suffer as well? In general, why is this not being addressed or taken seriously? You guys are developing feature after feature but are breaking essential systems that render these features useless. There is a much deeper issue going on here. Its not just Cloth. Anything with physics gets messed up by Temporal AA. So much so its just not useable.
I think OP is correct, and that it is also a motion blur issue. There are some work-arounds but with some pretty bad consequences. So if you have anything with physics in your scene, you either…
1: Turn motion blur all the way up to 1. But you get a very milky look in the render that isn’t desirable for cinematic production. Motion blur looks much more desirable for me at 0.2.
OR
2: You keep your Temporal AA sample at 1, and sacrifice higher quality edges, detail, dof and motion blur.
Both are difficult decisions to make with very unfortunate compromises.
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I’m on the latest UE5.2.1, hair is all over the place when rendered with anti-aliasing, temporal samples. Motion blur 1.0 works but its not really ideal.
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Sadly, no.
Is there a way to keep the subsamples but limit the seeds count?
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It is not fixed in 5.2. I’m having the same issue.
Hello,
To render it correctly you have to change the Hair Physics in your groom
In the solver choose “custom” the re-choose the correct solver exemple:spring.
I think there is just a pb in the niagara solver not linked correctly
Obviously you need the engine plugin content visible, the solver is Groom Content/Emitters/Niagara Systems
The issue was tested in 5.2 and was not fixed
Yeah, this is still broken (UE5.3). You can set motion blur to 1 and that will fix things (have no idea why). I’m not crazy about that much motion blur. You can always do your physics elsewhere and import in an alembic.
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Hey Tommy,
Have you tested in the latest 5.4 version ?
I have the same problem in 5.3.2 
I’m playing with it now. I’m seeing better cloth physics… I need to test hair. I still see some dynamic stuff moving around unaturally… but it looks like they are working on this issue.
Edit** After rendering a few things, I can see it’s still not working. Here’s my last test render at 32 TAA samples…
The best option I have found is to cache anything you can until they fix it. Its already known (from what I have heard) that they are working on hair simulation caching somehow. There is also a very janky way of caching cloth with chaos caching. If you have physics objects you should cache those. Niagara particles I ended up solving those completely by using their new cache system for NIagara.
This fixed it for me!
Select the groom component and set Simulation > Simulation Settings > Simulation Setup > Local Simulation to false
Same thing. Testing it with 5.4 - nothing changed
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