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Particle System Rendering Differently in Play Mode, But Not Always

Discussion in 'General Graphics' started by milanvanzanten, Sep 14, 2021.

  1. milanvanzanten

    milanvanzanten

    Joined:
    Oct 30, 2019
    Posts:
    6
    I'm fighting a seriously peculiar bug and I've run out of approaches trying to fix it.

    A particle system I have is being rendered & updated differently in play mode (see attached image). The particles seem to move slower in general.



    The weird part is, that whenever i tweak something in the particle system editor during play mode or - and here comes the weird part - do a print screen (what does this have to do with particle speed in unity??), for a short time (a few frames) the full system is visible again at it's usual speed.

    Things I already checked:
    • Particle count seems stable in both play and edit mode
    • Performance isn't an issue
    • Particles have a speed (apparently important)
    • Same thing happens with trails disabled
    • Same thing happens with external forces disabled
    • I'm not 100% sure, but it seems that if i disable both trails and external forces, they seem to render the same way in play and edit mode (though difficult to tell since that only leaves particles shooting out without trails)
    I'm really out of ideas here and would very much appreciate any hint as to how i might fix this.
     
  2. mgear

    mgear

    Joined:
    Aug 3, 2010
    Posts:
    9,350
    which unity version? if can you share unitypackage, could test it.

    but i'd report as a bug if nothing else comes up..
     
    richardkettlewell likes this.
  3. milanvanzanten

    milanvanzanten

    Joined:
    Oct 30, 2019
    Posts:
    6
    I'm running 2020.3.18 and on the built-in renderer.
    Sadly cannot share the project due to copyright constraints but I will gladly share any details about the particle system and anything that might influence it if anyone has a new approach how this could be tested.
     
  4. mgear

    mgear

    Joined:
    Aug 3, 2010
    Posts:
    9,350
    could test that does it happen in a empty project also?
     
  5. milanvanzanten

    milanvanzanten

    Joined:
    Oct 30, 2019
    Posts:
    6
    Okay, I have narrowed down the problem to the force field behaving differently in play mode. I'm attaching a package with a very simple scene where this should be apparent. With either the external forces module on the particle system disabled or the force field itself disabled, they seem to behave correctly in both play and edit mode.

    I'm confused though as to whether this is a bug with this specific configuration or if force fields always behave differently in play mode, since this is such a basic setup.

    Unitypackage:
    https://www.mediafire.com/file/f5mdmndn3j4e0t4/ParticleTest.unitypackage/file
     
  6. mgear

    mgear

    Joined:
    Aug 3, 2010
    Posts:
    9,350
    yeah definitely looks different in play vs edit modes,
    and in playmode if you move mouse it gets faster..

    * happens in newer version too, tested on 2021.2.0b10 also

    ** in 2019.4.19f1 it works as expected, same speed in play vs edit
     
    milanvanzanten likes this.
  7. milanvanzanten

    milanvanzanten

    Joined:
    Oct 30, 2019
    Posts:
    6
  8. richardkettlewell

    richardkettlewell

    Unity Technologies

    Joined:
    Sep 9, 2015
    Posts:
    2,281
    I was just looking at the versions that bug report landed in, too, before i saw your latest post!
    Yes I agree this bugfix may well have affected this. But in theory it should have made the behaviour more consistent, not less!

    Can you file a bug report with that unitypackage, and we'll take another look! Thanks!
     
  9. milanvanzanten

    milanvanzanten

    Joined:
    Oct 30, 2019
    Posts:
    6
    will do!
     
    richardkettlewell likes this.
  10. poopkinel

    poopkinel

    Joined:
    Dec 11, 2017
    Posts:
    4
    I am on Unity 2022.3.16f and still having this happening. Anyone with suggestions?
     
  11. OhmMu

    OhmMu

    Joined:
    May 8, 2016
    Posts:
    9
    bump