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Won't Fix
Votes
0
Found in
2021.3.38f1
2022.3.26f1
2023.2.20f1
6000.0.0f1
Issue ID
UUM-72120
Regression
No
Particle System Force Field behaves differently when in Play Mode than it does in Edit Mode
How to reproduce:
1. Open the “My project.zip“ project
2. Open the “SampleScene“
3. Select the Particle System GameObject in the Hierarchy
4. Expand the “External Forces“ section in the Inspector
5. Increase the Multiplier property to 2
6. Run the Particle System in the Edit Mode and observe the Scene view
7. Enter the Play Mode and observe the Game view
Expected results: Particles behave the same in Play Mode as they do in Edit Mode
Actual results: Particles in Play Mode collapse in the middle, in Edit Mode they do not
Reproducible in: 2021.3.38f1, 2022.3.26f1, 2023.2.20f1, 6000.0.0f1
Reproduced on: Windows 11 Pro (23H2)
Not reproduced on: No other environment tested
Note: Reproducible in the Player as well
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Resolution Note:
When combining Gravity or Direction force fields with Rotation forces, the applied force will depend on the framerate.
We acknowledge that this is problematic, especially due to the fact that particles in edit mode are force to be updated using a fixed time step of 0.02ms (~50FPS), while they can update faster in play mode.
This could potentially be solved by changing the order in which these forces are applied.
Unfortunately, this change this would mean that the values used for Gravity would differ greatly from the current ones (for example, from 20 to 8 in the provided case).
We can't risk causing regressions to other users, so the safest option is not to change it.
Under normal circumstances, the difference should not be too big (editor ~50FPS, play mode ~60FPS), but it could get worse if the performance is not good in editor, which could make it fall to 25FPS or less.
There is no easy workaround either, other than making sure to test the particle system configuration under real framerate conditions.