Crash after using 2 GPUS + Megascan asset + PathTracing (Assertion failed: !Geometry->IsDirty)

Development Getting Started & Setup
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1

Hi,

I recently configured my Unreal engine to use 2GPUs using the shortcut line + the r.PathTracing CMD code.

I’m using 2 Nvidia Geforce RTX 3090.

It works perfectly in Lumen, but in PathTracing, as soon as I drag a Megascan asset, UE crashes and get this error.

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Assertion failed: !Geometry->IsDirty(CommandContext.GetGPUIndex()) [File:D:\build++UE5\Sync\Engine\Source\Runtime\D3D12RHI\Private\D3D12RayTracing.cpp] [Line: 4134] Acceleration structures for all geometries must be built before building the top level acceleration structure for the scene.

UnrealEditor_D3D12RHI
UnrealEditor_D3D12RHI
UnrealEditor_Renderer
UnrealEditor_RHI
UnrealEditor_RHI
UnrealEditor_RHI
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_RenderCore
UnrealEditor_Core
UnrealEditor_Core
kernel32
ntdll

I already reported it but just sharing in case someone faced anything similar
Thanks!

2

Greetings @vvelasco

Welcome to the Unreal Engine Forums! Do you have any plugins currently running with this? If so, try disabling those and seeing if it’s perhaps one of the plugins causing the problem. I’d also try running it in DirectX 11 rather than 12 and see if that helps. I’ll monitor the thread for responses. I hope this helps!

3

Thanks for the quick response.

I’ll give it a try. But I have to use Directx12 because pathtracing only works this way, right?

4

Correct. If you’re using path tracing, I do believe it has to be with DirectX 12 or Vulkan. Let me know how it turns out.

5

Hi. Did you ever get this working? I have a similar setup - 2 x A6000 GPUs set up with SLI and following Alex Pearce’s video tutorial ( (64) Multi-GPU Tutorial in Unreal Engine! - YouTube) - but all I get is this crash every time I start the pathtracer. Runs fine on just one GPU with Pathtracing. Unreal 5.3.2