# Unstable particles at big delta time

**URL:** <https://forums.unrealengine.com/t/unstable-particles-at-big-delta-time/306571>\
**Category:** FX\
**Tags:** unreal-engine, UE4, question\
**Created:** [February 10, 2015, 6:45pm UTC](https://forums.unrealengine.com/t/unstable-particles-at-big-delta-time/306571 "2015-02-10T18:45:56Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Pierdek](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Pierdek](https://forums.unrealengine.com/u/Pierdek)\
**Post date:** [February 10, 2015, 6:45pm UTC](https://forums.unrealengine.com/t/unstable-particles-at-big-delta-time/306571/1 "2015-02-10T18:45:56Z")

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Hi

I found an issue in the particle system when the engine delta time comes to big values for example from 0.03 to 0.4.

Observe movie what happening with particles:

I also created a sample project where this issue can be easy reproduced:

> **[Dropbox - Error](https://www.dropbox.com/s/6xz0pawpmm5dhdd/particledeltatest.zip?dl=0)**
>
> Dropbox is a free service that lets you bring your photos, docs, and videos anywhere and share them easily. Never email yourself a file again!

1. start the gameplay
2. press and hold “Z” key to emit particles
3. press “E” to destabilise delta
4. observe the issue, some particles are teleported in the far distance from the character and some particles are reverted back.

This issue is really annoying when You want to create a particle effect which returns events from collisions.

I checked **4.6** , **4.7** and **promoted branch(4.8)** and I was able to reproduce this issue with my test project.

If you can’t make repro because you have “NASA computer”🙂 just edit MyCharacter blueprint and increase iteration counter in the for loop connected to “E” key.

Anyone has an idea how to fix this? Or where should I start.

Regards

Pierdek

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**Author:** ![Lovecraft\_K](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Lovecraft\_K](https://forums.unrealengine.com/u/Lovecraft_K)\
**Post date:** [February 11, 2015, 4:47pm UTC](https://forums.unrealengine.com/t/unstable-particles-at-big-delta-time/306571/2 "2015-02-11T16:47:41Z")

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Hey Pierdek -

Thank you for your report. I have entered a bug report for this issue. As we continue to investigate the issue, I will keep you informed, for reference UE-9630.

Thank You

Eric Ketchum

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**Author:** ![Pierdek](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Pierdek](https://forums.unrealengine.com/u/Pierdek)\
**Post date:** [March 24, 2015, 1:40pm UTC](https://forums.unrealengine.com/t/unstable-particles-at-big-delta-time/306571/3 "2015-03-24T13:40:11Z")

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Hi Eric,

any news about this issue?

Regards

Pierdek

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**Author:** ![Lovecraft\_K](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Lovecraft\_K](https://forums.unrealengine.com/u/Lovecraft_K)\
**Post date:** [March 24, 2015, 3:24pm UTC](https://forums.unrealengine.com/t/unstable-particles-at-big-delta-time/306571/4 "2015-03-24T15:24:38Z")

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Hi Pierdek -

This issue is currently backlogged but assigned.

Thank You

Eric Ketchum

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**Author:** ![Pierdek](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Pierdek](https://forums.unrealengine.com/u/Pierdek)\
**Post date:** [December 16, 2015, 11:27am UTC](https://forums.unrealengine.com/t/unstable-particles-at-big-delta-time/306571/5 "2015-12-16T11:27:56Z")

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Hi again, any news about this issue?

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<div class="post-metadata">

**Author:** ![Lovecraft\_K](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Lovecraft\_K](https://forums.unrealengine.com/u/Lovecraft_K)\
**Post date:** [December 16, 2015, 2:52pm UTC](https://forums.unrealengine.com/t/unstable-particles-at-big-delta-time/306571/6 "2015-12-16T14:52:06Z")

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Hi Pierdek -

It looks like this issue is still backlogged.

Thank You -

Eric Ketchum