Bug Particle System Flash With Wrong Size And Position

We have some Particle Systems with Shape and Mesh Renderer module enabled.
They flash on the screen sometimes, problem happend randomly and only last single frame.
It seems like some of the mesh vertices are moved to infinite far away.


I made a small demo scene to reproduce the issue.
[What's In The Scene]
1. Two particle systems with Renderer module enabled.
Render mode set to Mesh.
2. Two particle systems with Shape and Renderer modules enabled.
Shape set to Mesh.
Render mode set to billboard.
3. World space canvas with some Text.
4. All particle renderer use URP unlit shader. No custom shader involved.
5. GPU instancing is disabled in materials and particle renderers.

See attachment for scene package.

[Full Video]
Note 00:05. Sorry for the ugly looking

[Captured Error Frame]


[Unity Version]
- 2021.3.6f1c1
- 2021.3.7f1c1
- 2020.3.37f1c1
Not tested with other Unity versions

[Devices]
- Nox simulator latest version. https://www.yeshen.com/
- Mumu simulator latest version. https://mumu.163.com/
- HUAWEI Mate30E Pro
- HUAWEI Mate20 HMA-AL00

We have been working on this issue for weeks.
Any help would be much appreciated!

 

OK.
Ticket ID is IN-13833.

 

Hi @richardkettlewell,

I find another bug has similar appearance (Reported in IN-13969), maybe it's caused by same reason.
It's much easier to reproduce in Editor.

For the origin issue, I tested replacing some Particle System with simple MeshFilter+MeshRenderer, and didn't reproduce the problem.
But there are too much VFX made with Particle System's Mesh Renderer, we can't recreate all of them.

If there is any workaround, please inform us.
Thank you!

 

Finally I find a way to workaround.

For each ParticleSystem
1. Change cull mode to Always Simulate
2. Disable ParticleSystemRenderer module
3. For each frame, call ParticleSystemRenderer.BakeMesh() (and BakeTrailsMesh if trail module enabled) to make a mesh snapshot, and assign the mesh snapshot to a MeshRenderer.

Rendering ParticleSystem this way may be inefficient, but after playing with all the options I didn't find other solutions.
Hope Unity may fix this issue in comming update.

 

Hi @richardkettlewell,

is there any update regarding the issue with particles? I have encountered it after upgrading from Unity 2020.3.30f1 to the Unity 2021.3 LTS version. The bug exists in standard (build-in) rendering pipeline as well.

We have 100% repro, but only on one device: Samsung Galaxy S10 (Mali-G76 MP12) with OpenGL ES 3.0 Graphics API. I have tested multiple Unity versions: 2021.3.9f1, 2021.3.11f1, 2021.3.12f1

 

@richardkettlewell, We have the same problem with particles on built-in render system. But it's not only particles problem, I think it's cameras blending problem, because when we disable other camera without particles - particles camera work correctly.

Didn't reproduced on builds with Unity: 2020.3.28f1
Reproduced on builds with Unity: 2020.3.38f1, 2020.3.39f1, 2020.3.41f1, 2021.3.12f1

Devices where we can reproduce this issue:
- Samsung A51
- Huawei P40 Lite
- Huawei P30 Pro
- Emulator "LDPlayer 9"

Our issue example:
- camera 1 render background particles(solid color)
- camera 2 render shop item(depth only)
- camera 3 render ui
- sometimes we can see glitches(Link: see screenshots and video here(google disk))

We can fix problem any of the ways:
- downgrade Unity to 2020.3.28f1
- disable all particles on camera 1
- disable particles systems renderers
- stop all particle systems
- disable camera 1
- disable camera 2
- disable shop item on camera 2
- simulate particle system with time 0 - all particles freeze and no problems

We can lower the frequency of the issue:
- use render textures for cameras 1 and 2
- disable cameras and manual rendering to render texture from script on EndOfFrame

We can increase the frequency of the issue:
- simulate particles systems with speed x10

These steps don't help at all:
- change shaders for item or particles
- change materials for item or particles
- change some particle system settings
- change some cameras settings
- simulate particle systems manually on update, fixed update, late update, EndOfFrame
- disable cameras and manual rendering cameras from script on update, fixed update, late update
- change quality settings
- disable post processing on cameras
- disable support "open gles 2.0"
- change depth on cameras

The funny thing is that we can't use Unity 2020.3.28f1 due to crashes with Android SDK 31. Also we can't downgrade Android SDK to 30. From November 1, for apps with SDK <= 30, Google will stop showing the app in the store for devices with a system API >= 31(https://developer.android.com/google/play/requirements/target-sdk).
The only thing we can do to lower the level of crashes is to update Unity, but then there are glitches.

 

Hi, @llFlexford
Acoording to our test, Particle System works good in 2021.2.19f1. But it's not LTS version, so I don't know if it's an option to you.

But we can't down grade to 2021.2, because some 3rd party component we use are highly coupled with 2021.3.
And we use `ParticleSystem.BakeMesh()` each frame to work around the particle glitches bug.

 

We had the same problem.
It's a big headache.

 

@caogtaa We have particles without meshes

 

We've been similar weirdness with particles recently also, which I think are the same issue. Some observations about our case in case it is helpful tracking this down:

- the only device we know it happens on is a Galaxy S9. There are probably others, we haven't tested widely.
- we are using 2021.3.9f1 and OpenGLES3 graphics API.
- we recently upgraded from 2020.3.34f1, where the problem was not seen.
- we have a single orthographic camera.
- we've noticed the issue on at least 4 different particles systems, but it only seems to manifest for a frame before returning to normal.
- so far I only have noticed this on device (Android), and not in Editor.
- I have not been able to figure out a way of making it happen reliably. If I sit on a screen where one of the particles systems is showing continuously, it never seems to go wrong. Only when actually playing the game (when things are much more dynamic) it does wrong. This has hindered making a repro; I tried with one of the particles we've seen it happen on, but it doesn't seem to go wrong in the repro project.
- when it *does* go wrong, it seems like multiple particle systems (based on different prefabs and using different textures) are affected in the same frame. I have a couple of examples where the glitches show here: https://drive.google.com/drive/folders/1b53VTsAB8Gq6a2_LrmtO3QACfTULgT6D?usp=sharing. Note that on one of them the healing plusses and the sparking effects both glitch in the same frame. And in fact the particles being rendered don't seem to be rendered *wrong*; rather, there is something extra rendered that uses their (stretched) textures. This all makes me think the problem is not really tied to a specific particle, but perhaps to the rendering system as a whole.

 

Hi @AndyBlock, thank you for your informations.

Exactly what I see in my project, more than one particle glitch at the same frame.

In my case they are not extra things.
As my video shows, the yellow squres at right side "disappears". They are not rendered at right place but stretched.

Totally agree! I think it's related to initialization or reusage logic of internal vertex buffer.

 

Hi all!

We had the same bug in our project. And we waste a lot of time (about 2.5 months) trying to fix it.

It is easy to reproduce on many Huawei, Honor and Xiaomi devices with GPU Mali-G76, for example: Redmi Note 8 Pro, Huawei Nova 5t, Honor 20.

We have tested dozens of versions of Unity and found out that the bug first appeared in version 2020.3.34. In the Release Notes we found this entry in the 'Fixes':

• Particles: Fixed a particle flickering. (1415307)

But this ticket does not exist in the Issuetracker. Looks like a possible cause of this problem.

Please, @richardkettlewell , you're only our hope.

 

Hello, is it convenient to fix this problem, or is there any other solution

 

Hi @richardkettlewell , we also found this bug in our project. The particle system we use glitch in random cycles. Our bug is exactly the same as the description.

• unity version: 2020.3.39
• device: mumu 163 or ldmnq emulator

We finally catch one frame by renderdoc (check the image). The small particles connect with each other. It seems the faces or vertexs get wrong. Sometime the particle system use wrong texture from different particle system.
We cannot reproduce the flash case in a scene with single particle system, and editor is always right. We also doubt if the emulator performance might effect the frequency. It seems the render data sent from game engine is wrong in one frame. Root cause cannot be found.

Do you have any suggestion? What can we modify in unity to avoid this bug?

 

any updates on this?

 

No here.

 

I was experiencing a similar issue with particles in android. I found out that the problem occurs when Unity uses OpenGLES 3.0 as Graphics API. I deleted OpenGLES 3.0 and put Vulkan and OpenGLES 2.0 instead and my issue is gone.

 

its not activated
In addition, for me this error only occurs on certain devices, e.g. the samsung s9+ (android 10)

 

We have also submitted yesterday a bug report (IN-25911) for an issue that seems very close to that discussed in this thread.

This issue appeared when we upgraded to Unity 2021.3.9f1 from 2020.3.17f1.
We were using the Auto graphics API, but as you know the default graphics API for 2020 was OpenGLES3 and for 2021 Vulkan. The problem is that on many low end devices, the performance of Vulkan in 2021 is much much worse. In some cases up to 7ms worse performance. So we tried to disable the Auto Graphics API and use OpenGL ES3 first. OpenGLES3 is indeed as fast as it was in 2020 version but, to our dismay, we found that on devices like Huawei P30 Lite and Samsung Galaxy S9 that use a Mali GPU (and possibly many others we have not been able to test) this glitch appears. This issue happens very often on many screens of the app and we cannot ship it like that. And if we go back to 2020 version, we will lose our target market in HTML5/WebGL as unity 2020 does not support the ETC2 texture format that we need for mobile, and also our developers that use M1 based macs will have very bad performance in the editor.

So an urgent fix is very much needed here

----------------

As an additional info, when this glitch occurs most if not all of the particles visible on the screen are distorted/stretched and some times we see in the distorted area parts of a sprite atlas.
Also, if it helps, the Graphics Jobs are disabled.

We have been able to reproduce it in: 2021.3.9f1, 2021.3.15f1, 2022.1.23f1
We have not been able to reproduce it in: 2020.3.17f1

Reproduced with:
Huawei P30 Lite (MAR-LX1A) (Chip: Kirin 710, Gpu: Mali-G51, Android 10)
Samsung Galaxy S9 (Gpu: Mali-G72, Android 10)
Bluestacks App Player 5.9.610.1005 N32 (OpenGL graphics renderer) on Windows 11 with NVIDIA Geforce RTX3060 Mobile

This is how it looks on one frame that the glitch appears:

And here is how it looks on the next frame of the animation that no glitch occurs:

 

@richardkettlewell Happy New Year! Do you have any news about this bug?

We have the same problem. It reproduces only on Mali-G72-78 devices. We fixed it to turn off Multithreaded Rendering, but we have low performance on such devices now.

 

Our team repoduce this bug in 2021.3.9 in both editor environment(window) and android enumerator. Our project setting disable graphic job and enable multi threads rendering. By capturing frame in renderdoc we are sure we encounter the same problem as then mesh produced from particle system get wired position. I wonder for 2021.3, which version should we use to avoid this problem

 

If you have any proposed workarounds in the meantime let us know. We are on a bit of a tight timeline at the moment. Cheers .

Edit: We're in 2020.3.30f1. Disabling GPU instancing on our mesh based particle rendering seems to have resolved the issue as a workaround.

 

we are in exactly the same situation, we are running 2020.3.40f and can't downgrade due to crashes, the particles are a big part in our game so turning them off is not an option (lots of cosmetics the users can buy)
The only thing we can do it's wait for a patch :/

Are you guys working on this? @richardkettlewell

 

Looking forward for it. We have the same issue over multiple projects now.

 

Glad to hear that. BTW just want to remind you that this bug appear not just in build for android and vulkan. We encounter that in editor environment too.

 

Can I know how this bug occurred? I think this problem occurs spreadly before, but seems not so many?
BTW, our team use 2020.3.

 

Great news! May I ask for an estimated release date for the 2021.3 LTS that will include the fix?

 

This is very concerning, we recently migrated from 2019 to 2020 just to avoid crashes with the API level 31, but this brought dozens of new errors and things to fix (our game started with Unity 5.6..) each migration gets harder and always more ANRs

 

We have just upgraded our project from 2019.4 to 2020 LTS. We can not upgrade it once more due to our deadlines. Please provide a fix for 2020.3 also. Some people here have indicated that this bug appeared from a certain version of 2020.3 , wouldn't it be possible to undo the changes that is causing this problem ?

 

Our project just updated to 2020.3. This update also required a lot of schedule and cost. Update to 2021 soon after this is not realistic at all. Support for 2020.3 is also required. And quickly! Please respond.

 

so if won't fix in 2020, what can we do to avoid this? Our game will test next month, it's no time to update.
btw, when will 2021.3's patch be release?

 

I hope this fix can be patched to 2021.3 soon, it's really important to us.
Our game will test in next month.

 

Thank you for your reply. I understand that support is about to expire. However, at the same time, it is also true that problems are occurring in the game that is running and that it takes a lot of time to upgrade Unity. The best condition is to be able to fix bugs in 2020.3. I think that there are various difficult things, but please consider and respond.

 

Hello, glad to hear that bug is fixed in specific Unity version. We are using 2021.3.x , will the next 2021 LTS release contain the fix?

 

Please let me confirm one thing.

I don't think you've seen any reports other than Android in your conversations so far.

Is Android the only platform where this problem occurs?

 

Modify the Unity version to 2020.3.33 available