Scene crashes on opening after deletion of Metahuman hair LOD

Development Rendering
, ,
1

A simple scene with backdrop and a metahuman in UE 5.0.3 using the Film/Video & Live events blank template. We used hair that was in development as it was the closest match for our reference, though it would disappear when the camera got too far away. I deleted all LODs from this other than 0-1 which fixed this issue and had pressed play without the scene crashing on at least one occasion.
I was attempting to get the toggles of the characters jumper to accept gravity in editor as it does at runtime and pressed play, which is when the scene crashed.

Following advice online I have tried cutting first the cachedassetregistry.bin out of the “C:\Users\Sam\AppData\Local\UnrealEngine” folder and then the whole 5.0 engine version from the same folder but to no avail. Its a fairly simple scene to recreate but I’d rather understand the issue and how to troubleshoot. If anyone is able to repsond please give it to me in laymans terms as I am still fairly new to Unreal!

Error message is as follows:

Assertion failed: StrandsLODCount <= LODScreenSizes.Num() [File:D:\build++UE5\Sync\Engine\Plugins\Runtime\HairStrands\Source\HairStrandsCore\Private\GroomComponent.cpp] [Line: 2700]

Thanks

3

Thanks for posting this. I am also experiencing the same problem. Tried 3 different online solutions (link below) to fix the hair from disappearing, but no luck with any of them. Maybe it might work for you. Otherwise, hopefully someone has a fix soon. Cheers

1 - delete LOD

2 - LODsync

2 - Check “Onclude Components into Bounds”

4

So I couldn’t figure out why it crashes, but I finally found a solution to the disappearing hair problem and it has to do with the LODsync as mentioned in the above link. Instead of just creating a new LODsync component in the Metahuman’s BP, I copied and pasted the LODsync from the original BP, which contains the info for “Components to Sync” and “Custom LODMapping”. Then changed the value of the “Forced LOD” to 1 (because my Metahuman only had 0 and 1 LODs). And it worked! No more crashes and hair doesn’t pop in and out any more =')

I am also a newbie, but hope this helps. Good luck

5

Hello! I have the solution to this problem

Create a brand new project and import the MetaHuman in question that you deleted the LODs from the groom from (mine is Vivian)

Then delete the asset from the broken project and copy over the asset from the new project (mine was Hair_L_StraightBangs.uasset) mine had a difference of 1 KB (just the deleted LODs from 3 to 8)

I also deleted the intermediate folder but that probably isn’t necessary and would just force you to recompile

Until the bug is fixed don’t try to delete LODs from the groom asset… just use Forced LOD to 0 or 1 and don’t try to spawn too many MetaHuman on one map with this type of hair

Hope this helps someone!

1 Like