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Unreal Crash: Assertion failed: InstancingRandomSeed != 0

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TiRi2501
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Hi all!

For a few days I have been getting errors when trying to instantiate some Static Meshes inside Unreal.

Assertion failed: InstancingRandomSeed != 0

This error happens on Digital Assets that 100% worked before.
I tried to isolate the defective instance points, but which instance causes the crash is inconsistent. Some instances that triggered the crash reliably before work fine in the next session...
I also tried explicitly setting @unreal_InstancingRandomSeed = 0 but the error persists.

Any idea what causes this and how to fix this?
Any help is greatly appreciated

Houdini: 20.5.278.0
Houdini Engine: 7.0.0
Unreal: Version: 5.4.3-34507850+++UE5+Release-5.4

The last lines of the Unreal Crash Log:
[2024.08.15-10.56.36:548][321]LogHoudiniEngine: Warning: Creating Static Meshes: Object [0 bgeo_parser1], Geo [3], Part [4 file1_4], unable to retrieve LOD screensizes
[2024.08.15-10.56.36:554][321]LogStaticMesh: Display: Building static mesh object_bgeo_parser_1_0_0_3_4_main_geo (Required Memory Estimate: 0.010968 MB)...
[2024.08.15-10.56.36:555][321]LogStaticMesh: Built static mesh [0.00s] /Game/HoudiniEngine/Temp/object_bgeo_parser_1_0/8505F0F9/object_bgeo_parser_1_0_0_3_4_main_geo.object_bgeo_parser_1_0_0_3_4_main_geo
[2024.08.15-10.56.36:558][321]LogHoudiniEngine: CreateStaticMesh_MeshDescription() executed in 0.020179 seconds.
[2024.08.15-10.56.36:759][321]LogOutputDevice: Warning: 

Script Stack (0 frames) :

[2024.08.15-10.56.36:773][321]LogWindows: Error: appError called: Assertion failed: InstancingRandomSeed != 0 [File:D:\build\++UE5\Sync\Engine\Source\Runtime\Engine\Private\InstancedStaticMesh.cpp] [Line: 2250] 


[2024.08.15-10.56.36:773][321]LogWindows: Windows GetLastError: The operation completed successfully. (0)
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Cody Spahr
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It seems like this might be an Unreal issue. If you think it is a Houdini Engine bug, please submit a bug report. Attaching any files helps us a lot too with fixing these things. A bug report will prioritize this issue for our devs and get you assistance faster.
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TiRi2501
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After a day of debugging I found that this error occurs when the HDA is instantiating a mesh that is not loaded in memory.
If I manually instantiate the meshes before cooking my HDA, it works fine.

Does Houdini Engine not load assets not in memory before trying to instantiate them? Is this really an error on the Unreal side?
Or is there a setting that forces/ prevents this?

A hotfix would be to create a small asset zoo with all assets that are referenced by the HDA, which is not a sustainable solution though.
Edited by TiRi2501 - Aug. 16, 2024 05:26:24
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andy_sidefx
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The log looks like its trying to create mesh, not instance one. But when instancing meshes, the plugin should load the meshes automatically.

The best thing to do would be to submit a Houdini Engine bug report.
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Eetu_Mainframe
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Joined: Dec. 2019
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I just upgraded from 5.3 to 5.4 and immediately ran into this same issue.
It doesn't happen with every staticmesh, but I haven't been able to pinpoint what exactly is the trigger. Very simple meshes seem to work, more complex meshes seem to crash. Instantiating the mesh into the level before running the HDA makes everything work, as @TiRi2051 found out, but that is not feasible for me either.

I have a vague recollection this used to be a problem before, with blueprints, maybe in the 4.27 era or something... (EDIT: found it, bug ID# 118587 in 5.0 was a bit similar)

I'll try and figure out an easily submittable repro

Win10
Houdini & Plugin 20.5.422
Unreal 5.4.4

----------
EDIT: Bug submitted as ID# 142696
Edited by Eetu_Mainframe - Nov. 25, 2024 13:35:49
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Eetu_Mainframe
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Epic came up with a small fix to UE that seems to fix this. It is available in their github as CL38475840, for those that compile their own engine. Maybe the fix will be included in a future 5.4.x release, I don't know...

This issue is also 5.4 only, 5.3 or 5.5 work.
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