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Mesh particle system flickering (URP)

Discussion in 'General Graphics' started by Radagasd, Dec 24, 2021.

  1. Radagasd

    Radagasd

    Joined:
    Mar 1, 2015
    Posts:
    6
    Hey,

    When I have a lot of particle systems using meshes, my the rendering of the particles starts flickering in and out (see the video). I'm not sure what's going wrong or if this is just a limitation of Unity. I'm using Unity's URP lit particle shader, the default sphere mesh and mostly default particle system settings.



    If you want to recreate this problem you can do as follows:

    Create a new URP project (Unity 2020.3). Add a new particle system (PS) to the sample scene. Change the PS Render Mode to mesh and set the mesh to the default sphere. Create a new material using the shader: Universal Render Pipeline/ Particles/Lit and set the PS material to this new material (the material will ask you to fix the Custom Vertex Streams by clicking the button). Make a lot of copies of the PS (~20 in my case) and run the scene. The PS rendering starts flickering.
     
    Radagasd, Dec 24, 2021
    #1

  2. richardkettlewell

    richardkettlewell

    Unity Technologies

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    Sep 9, 2015
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    2,285
    Please submit a bug report
     
    richardkettlewell, Dec 28, 2021
    #2

  3. Radagasd

    Radagasd

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    Mar 1, 2015
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    I did, but it hasn't been reviewed yet and thought perhaps someone here has experienced it as well.
     
    Radagasd, Dec 28, 2021
    #3
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  4. smeas

    smeas

    Joined:
    Sep 30, 2019
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    3
    This looks quite similar to an issue I am having. I'm using particle systems with multiple meshes, selected at random per particle. While they're flickering, it looks as if the meshes of the particles are getting swapped (and maybe their size as well?). The flickering only happens in play mode, and only on some computers. I found that if I disable 'GPU Instancing' under the 'Renderer' module, the flickering goes away.
     
    smeas, Jan 11, 2022
    #4

  5. Radagasd

    Radagasd

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    Radagasd, Jan 11, 2022
    #5
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  6. Stormwalker

    Stormwalker

    Joined:
    Apr 18, 2013
    Posts:
    1
    Can confirm turning off GPU instancing solved it.
    That is most unfortunate.
     
    Stormwalker, Feb 19, 2022
    #6
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  7. _geo__

    _geo__

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    Feb 26, 2014
    Posts:
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    Still got this on 2021.3.4f1. Can also confirm that disabling mesh gpu instancing works to fix it (URP, Android, linear colors space).
     
    _geo__, Jun 9, 2022
    #7

  8. richardkettlewell

    richardkettlewell

    Unity Technologies

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    We still have a backport in progress for 2022.1 and 2021.3 for another issue that causes this flickering. So I am hopeful that will fix this. The bad news is that the issue i'm talking about isn't public in our database, so there is no issue tracker link for it. i've no idea why that is :(

    It looks like it's on track for 2021.3.5f1 though, due for release sometime on or after the 22nd June. Sorry for the inconvenience. If it still happens in that version, I'd say we'll need another bug report, unfortunately.
     
    richardkettlewell, Jun 9, 2022
    #8
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  9. _geo__

    _geo__

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    Thank you very much or the info on that. At least it's a known issue and being worked on. That's good news :)
     
    _geo__, Jun 9, 2022
    #9
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  10. reza-kamousi-magna

    reza-kamousi-magna

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    Nov 10, 2022
    Posts:
    1
    any news regarding the solution in 2023? :)
     
    reza-kamousi-magna, Jan 20, 2023
    #10