Graphics corruption / performance drop with GPUSim Niagara ribbon on AMD GPUs introduced with UE5.6

Development Rendering
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1

Hello,

UE5.6 introduced graphics corruption/perf drop with certain GPUSim Niagara ribbons on AMD GPUs compared to normal behavior in UE5.5.

Sample project that demonstrates the issue is attached with description above.

When captured in PIX/RenderDoc one can see that the parameters that drive indirect draw indexed of the ribbon emitter are corrupted ie very large number of indices(giga order) is requested to be drawn likely leading to indexing outside out the valid range of the geometry buffers.

Thank you.

JiriS

2

Steps to Reproduce
Use PC with AMD GPU (issue reproduces on variety of models and drivers on our side - series RX6000, RX9000, on latest drivers or 1 year old as well)

Open sample project in vanilla UE 5.5.4 - everything looks and performs normal

Open sample project in vanilla UE 5.6.1 - performance tanks to single digit FPS and visual corruptions with the ribbon emitters can be observed on screen

3

It seems that this is the same issue discussed here: [Content removed]

I merged the CL 44042760 from //UE5/main and locally it fixed the issues, will wait for QA to confirm.

JiriS

4

Hi Jiri,

That’s the only recent fix I’m aware of, hopefully it fixes the issue.

Thanks,

Stu

5

Thanks for letting me know!

6

The fix seems to be holding well.

Thanks

JiriS