Collision inverts when negatively scaling assets (Custom Static Mesh)

General Issues and Bug Reporting
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1

Please select what you are reporting on:

Unreal Editor for Fortnite

What Type of Bug are you experiencing?

Assets

Summary

When importing a custom .fbx Static Mesh into UEFN from Blender and then scaling it negatively (to flip the object), the collision becomes inverted

Steps to Reproduce

  1. Import a custom .fbx file with custom collision set up, using the naming convention UBX for collision volumes. Do not generate missing collision upon import.
  2. Drag asset into level.
  3. Type -1.0 into either the X, Y, or Z Scale.
  4. Collision is now inverted (can be viewed in Lighting Mode: Player Collision)

Expected Result

The collision should not be inverted based on how the mesh is scaled.

Observed Result

Imgur

Platform(s)

UEFN PC

2

Turns out this is likely just visual bug with the Player Collision visibility mode

2 Likes
3

Sorry to necro post this. But I want to share that in all my years of doing Unreal Engine and I had been doing it since before 2019 this is the first time I found this issue.

I was developing a low poly pack for UE4 with custom collisions. Everything worked well there. Same with UE5.0.

But in one of the reviews I was told something about the collisions while in approvals, still in approvals as of writing this. The thing is that for some reason from UE5.1 all the way to today 5.7 as of writing this 11/27/2025 all my meshes that were not custom collided from blender. I made custom collisions there… returning, are inverted. So the default imported meshes from UE with automatic generated collisions seems to be for some reason inverted. The custom colllision ones from blender work fine.

I have no idea what causes this, first time I ever find it. I went to google to research more information about this but I only found your post regarding this specific situation. Thank you so much for creating this post. I wanted to share this in-case anybody is in the same boat.

As of right now most of my meshes are either transform 0,0,0 from blender or with rotation of -90. Both which do not have custom collisions are again or appear inverted. But if you play the level or map, etc. the collisions work fine.

It may be a bug with viewer. The only solution I found right now is to re-export the mesh from engine via the Reimport option from the right click drop-down menu. That seems to fix the collision in-view for me.

What a weird bug, I hope it is just a glitch or bug but just wanted to share that. A very bizarre one for sure.

Thanks again itsanate for creating this post. Wish you all a great day and hopefully nobody experiences this bug in the future. Really odd bug.

Have a nice day!

J