# Very bad regression with AddInstance for HISMC in 4.19, wind gets reset for all existing instances

**URL:** <https://forums.unrealengine.com/t/very-bad-regression-with-addinstance-for-hismc-in-4-19-wind-gets-reset-for-all-existing-instances/428575>\
**Category:** Asset Creation\
**Tags:** unreal-engine, Instanced-Mesh, question\
**Created:** [July 3, 2018, 12:42am UTC](https://forums.unrealengine.com/t/very-bad-regression-with-addinstance-for-hismc-in-4-19-wind-gets-reset-for-all-existing-instances/428575 "2018-07-03T00:42:26Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![John\_Alcatraz](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@John\_Alcatraz](https://forums.unrealengine.com/u/John_Alcatraz)\
**Post date:** [July 3, 2018, 12:42am UTC](https://forums.unrealengine.com/t/very-bad-regression-with-addinstance-for-hismc-in-4-19-wind-gets-reset-for-all-existing-instances/428575/1 "2018-07-03T00:42:26Z")

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Theres a very bad bug in 4.19 and 4.20 with HISMCs.

This is 4.18:

![](https://d3kjluh73b9h9o.cloudfront.net/original/4X/b/6/0/b60d623804cea626997d9cc5659915a8839b4edd.gif)

This is 4.19:

![](https://d3kjluh73b9h9o.cloudfront.net/original/4X/6/7/3/67360774c5be6545c4523336d21d529ebc0d00f5.gif)

The wind for all existing instances seems to get reset when a new instance is added in 4.19. I’ve also tested 4.20, and that has the same bug like 4.19.

Here’s the 4.19 project where I recorded the GIF with: [HISMCTest419\_.7z - Google Drive](https://drive.google.com/file/d/18MoQ280TLuOcS69rzgjOu_8DHYON1mX8/view?usp=sharing)

To see the same, hit simulate in the TestMap level.

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<div class="post-metadata">

**Author:** ![John\_Alcatraz](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@John\_Alcatraz](https://forums.unrealengine.com/u/John_Alcatraz)\
**Post date:** [July 4, 2018, 8:53pm UTC](https://forums.unrealengine.com/t/very-bad-regression-with-addinstance-for-hismc-in-4-19-wind-gets-reset-for-all-existing-instances/428575/2 "2018-07-04T20:53:42Z")

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Actually, that HISMC bug is even worse. It does not just happen when you add a new instance, it also happens when you update any existing instance. So if you have a tree thats growing or something similar, all existing trees in that HISMC will get their wind reset.

![](https://d3kjluh73b9h9o.cloudfront.net/original/4X/f/5/4/f543f102a55c666eb9b55c8074210ef63f43ea4a.gif)

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<div class="post-metadata">

**Author:** ![John\_Alcatraz](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@John\_Alcatraz](https://forums.unrealengine.com/u/John_Alcatraz)\
**Post date:** [July 5, 2018, 9:02am UTC](https://forums.unrealengine.com/t/very-bad-regression-with-addinstance-for-hismc-in-4-19-wind-gets-reset-for-all-existing-instances/428575/3 "2018-07-05T09:02:05Z")

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There is a “fix” for this that “works”:

If there’s any static mesh existing and visible in the level with the same mesh like the HISMC, the issue does not appear.

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**Author:** ![anonymous\_user\_942e8e52](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_942e8e52](https://forums.unrealengine.com/u/anonymous_user_942e8e52)\
**Post date:** [July 11, 2018, 5:27pm UTC](https://forums.unrealengine.com/t/very-bad-regression-with-addinstance-for-hismc-in-4-19-wind-gets-reset-for-all-existing-instances/428575/4 "2018-07-11T17:27:49Z")

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Hello ,

Thank you for the report, this has been entered as [Unreal Engine Issues and Bug Tracker (UE-61621)](https://issues.unrealengine.com/issue/UE-61621)