Has anyone had trouble with the UE4 fogsheet (BP_FogSheet) in 4.23?

I recently upgraded to UE 4.23 and have found that the Unreal Engine BP_FogSheet asset (Found in the particle cave and blueprint learning projects) seems to have died for 4.23. It’s in an issue I’ve encountered in multiple ongoing projects, and when trying to upgrade a project to 4.23 or migrate the asset to new 4.23 projects.

The BP_FogSheet asset works in the Particle Cave project and Blueprints project for 4.23. You can make new levels etc and the asset works as expected. However, if you create a new 4.23 project or have an existing 4.23 project (including other UE supplied learning projects, e.g. content examples) and you migrate the asset over, it will always be completely blank when you try and add it to a level.

We’ve tried a bunch of ideas and have been troubleshooting on and off for weeks to get around it. There have been some ok-ish results by tweaking the fog sheet material, but nothing matches up to the effect of the layered fog sheets in our projects.

From what we’ve found, project render settings, config settings, level world settings or post-process settings are not the cause for the fogsheet blueprint to be blank. We’re stumped!

Any advice from anyone experiencing the same issue would be greatly appreciated.

After hours of debugging this, I got it work.

I have no idea why, but it’s the static mesh (SM_FogSheet_Plane.uasset). If you move it inside of UE4, duplicated, rename it, or whatever, it scrambles something to do with the FBX source path. So go ahead and migrate the whole group of files to where ever you want in your own project. Then manually copy this one file from the original Blueprint project to your new directory location (overwriting the migrated one). Re-link it to the BP if necessary.