URGENT - Help regarding Assertion failed: ScratchBufferRequiredSize + ScratchBufferOffset crash when pathtracing

Hello!
I am sorry for posting like this but I have a deadline in 9 hours and of course this is the time when stuff decides to go all wrong again.
I’ve been having this specific engine crash when using the pathtracer for on-and-off 3 days now.
Originally I found out that empty “null groups” (group left behind after merging actors that originally were part of said groups) was causing it. Crash stopped after I noticed and deleted said groups.

Here is the crash:
Assertion failed: ScratchBufferRequiredSize + ScratchBufferOffset <= ScratchBufferSize [File:D:\build++UE5\Sync\Engine\Source\Runtime\D3D12RHI\Private\D3D12RayTracing.cpp] [Line: 4431] BLAS scratch buffer size is 337380352 bytes with offset 11223082399744 (11059545312256 bytes available), but the build requires 4551680 bytes. UnrealEditor_D3D12RHI UnrealEditor_RHI UnrealEditor_Renderer UnrealEditor_RHI UnrealEditor_RHI UnrealEditor_RHI UnrealEditor_Core UnrealEditor_Core UnrealEditor_RenderCore UnrealEditor_Core UnrealEditor_Core kernel32 ntdll

The render ran fine this afternoon (around 2PM). Now it’s 10PM and the only changes I have done are that I added many Planes with 36 different materials that are all referenced in sequencer as they have animated parameter values.

My specs are:
i9 13900K
128GB RAM (4800)
RTX3090 24GB

The engine crashes right after engine warm-up frames are finished.
Also running with 512 path-tracer samples per pixel (Trying to render a lookdev preview to get an idea about something in the scene). It ran fine with 2048 samples previously, and even 4096 before then.

Please, any help would be greatly appreciated.
Thank you.

1 Like

FOR ANYONE ELSE WHO HAS THE SAME ISSUE:

The BLAS buffer handles geometry! This is a result of too much too complex NON-NANITE geometry! If you have complex static meshes in your scene that you do not need to be non-nanite, switch them over to Nanite!
Your issue should be fixed!

Hope this helps.

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