Removing a ISMC instance makes the last added mesh instance invisible

I have be able to recreate this issue in a test project which can be downloaded here | Control Panel , when removing a instance static mesh from a instance static mesh component using the blueprint node, the last added mesh instance seems to disappear its collision seems to remain but can’t be seen in run-time using F1.

Steps to reproduce

  1. Start the Project use key ‘1’ to spawn a ISM block, place 4 down
  2. then view the 1st placed block and use key ‘2’ to remove it ( ISSUE ONE )
  3. now remove block 3 and block 4 will reappear ( ISSUE TWO )

There is also a 3rd issue which comes up, where the removing mesh instance will be removed but only its collision the mesh is left behind.

Any Epic staff please review this bug.

This was fixed in 4.17.2 or 4.18 Preview 3

Thanks, Michel!

Hey, OverRated_AU; I can verify that this is working as expected in 4.18 Preview 3.

Thanks for the update Michel.

Hi Michel, This issue was fixed but seem its been brought back as I’m getting the issue now in 4.18.2?

Hey OverRated_AU,

I just tested this using the project you provided in your original post, but I’m not seeing the same results. Could you post repro steps from opening that project?

Hi TJ, I think its because the behavior is a bit different but the bug is the same, heres a easy way to test this issue, place down 5 blocks remove 2 you will see 5 disappear, then try to remove 3 it won’t be removed instead only the collision gets removed, thanks for the reply.

Here is what I’m seeing in 4.18.2-3794801 with those steps. I’m not seeing any other blocks disappear when the intended block is removed. Is there something I’m missing?


Ah sorry, i forgot to change the debug project to 4.18, so here’s the issue with 4.18. place down 5 blocks remove 2 then place down another block 5 will disappear, sorry for the confusion.

Hey, I just realized this one was close to my bug error too. OverRated_AU, maybe my project also shows the same behavior that you’re referring to? I do something similar to you, where I add a bunch of instances at once, then I subtract an instance but add an instance below it.

It sounds like the problem is generated by the order:
Add some instanced meshes
Subtract some instanced meshes
Add some instanced meshes
Subtract some instanced meshes but not the first one of that series and they’ll disappear.

I used ISMC for a lot of things in my project, mainly my building system so this is a game breaker bug for me, I hope its reported soon so i can be fixed, the 4.17 issue was fixed quite fast seeing this is a large bug being on one of the core mesh components.

Make sure to up vote it :).

Same. It’s actually what’s forcing my development to stay on 4.16 because 4.17 broke the feature and 4.18 kind of fixed things but kind of not.

I believe you are seeing a bug that I logged a few weeks back. JIRA UE-53053

It’s still being investigated by our devs but it is something we would like to get fixed soon. We are targeting 4.19 but that could change depending on how complex the fix is.

Thanks TJ for the info, ill await the fix.

im in 4.17.2 and i still have this bug

This bug was fixed, the one we are discussing after hasn’t you can view it here Unreal Engine Issues and Bug Tracker (UE-53053)

For me, the bug is not exactly the same.
I do not add anything in the array but I have an element that disappears when I destroy another one
(I do not spawn any element in game, I just have an instanced static mesh component in an actor that is spawn in game)

Did you try 4.19 Preview 2 since this fixed my issue? (I’d assume OverRated_AU’s issue too but I don’t want to overstep here.)

Unreal Engine Issues and Bug Tracker (UE-53053) <—The bug fix.