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Particle systems and gravity

Discussion in 'Physics' started by unity_2e_7kz8DqNKDjA, Feb 12, 2018.

  1. unity_2e_7kz8DqNKDjA

    unity_2e_7kz8DqNKDjA

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    I'm writing a game that takes place on a spherical planet. Therefore, the gravity vector should be directed to the centre of the planet. I have 2 particle systems at different points on the planet. So whatever direction I might set Physics.gravity to, it will be wrong for one of them. Is it possible to give each particle system its own gravity direction?
     
    unity_2e_7kz8DqNKDjA, Feb 12, 2018
    #1

  2. richardkettlewell

    richardkettlewell

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    It’s not possible using the physics gravity directly, but you could do it using the Force over Lifetime module.

    If you can write a script, you could set the force direction and strength for each system.

    https://docs.unity3d.com/ScriptReference/ParticleSystem.ForceOverLifetimeModule.html

    And a link to how to set the X axis only, with an example: https://docs.unity3d.com/ScriptReference/ParticleSystem.ForceOverLifetimeModule-xMultiplier.html

    Just set up the x, y and z axes, with the vector you want, by modifying that example script.
     
    richardkettlewell, Feb 12, 2018
    #2
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  3. richardkettlewell

    richardkettlewell

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    Update: In 2018.3, you can add a spherical Particle System Force Field Component to achieve spherical gravity! (CC @AcademyOfFetishes )
     
    richardkettlewell, Jan 31, 2019
    #3
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  4. ReadyPlayGames

    ReadyPlayGames

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    I played around with the Force Field Component for far longer than I should have. It's really cool.
     
    ReadyPlayGames, Jan 31, 2019
    #4
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  5. Gillissie

    Gillissie

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    What if I just want to change the direction of gravity overall? I can't seem to figure out how to do that with the Force Field Component. It always wants to pull towards the transform point.
     
    Gillissie, Apr 3, 2021
    #5
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  6. amitDklein

    amitDklein

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    Unity 5.0: there's a Gravity Modifier input that lets you determine the effect of world gravity on the particles
    Just change it to 1 and you will have gravity

     
    amitDklein, Aug 24, 2021
    #6
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  7. richardkettlewell

    richardkettlewell

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    richardkettlewell, Aug 24, 2021
    #7

  8. OldAntelopes

    OldAntelopes

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    Anyone know if the gravity in the ParticleSystemForceField is calculated 'properly' (as in its inversely proportional to the distance squared) or if its the same force applied irrespective of distance?
    (I think it seems to be the latter which is .. a pain (if you're using particles to represent large-scale gravitational bodies :] ) ). Assuming that conclusion is correct, can anyone recommend an approach for changing particle force behaviour directly? e.g. Have a specific update function per particle?)
     
    Last edited: May 20, 2022
    OldAntelopes, May 20, 2022
    #8

  9. richardkettlewell

    richardkettlewell

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    This sounds like a great use for our C# job system support. You can write a particle job, and compile it with Burst for great performance ;-)
     
    richardkettlewell, May 21, 2022
    #9

  10. OldAntelopes

    OldAntelopes

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    Thanks for the pointer, Richard.. I'm relatively new to the engine and haven't got to the job system yet.. Will have a dig, thx :)
     
    OldAntelopes, May 22, 2022
    #10

  11. richardkettlewell

    richardkettlewell

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    richardkettlewell, May 23, 2022
    #11
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