Lumen HWRT Crash at Startup on Radeon

Development Pipeline & Plugins
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1

AMD Ryzen 9 9950X3D (latest chipset driver)

Radeon RX 7900 XTX (any 2025 driver)

When we enable hardware ray tracing in the Editor, everything works fine. However, after restarting the Editor it crashes, and the project won’t launch unless you disable HWRT in DefaultEngine.ini.

You can reproduce this in an empty UE5.6 project from the Launcher. A Shipping build runs correctly if you switch on HWRT during gameplay via the console variable:

r.Lumen.HardwareRayTracing 1

NVIDIA GPUs do not exhibit this crash.

We tried following cvars from similar questions:

r.PathTracing=False

r.RayTracing.UseReferenceBasedResidency=False

r.Lumen.HardwareRayTracing.LightingMode=2

r.Lumen.Reflections.HardwareRayTracing.Translucent.Refraction.EnableForProject=False

r.RayTracing.Shadows=False

r.RayTracing.Geometry.NiagaraMeshes=0

r.RayTracing.Geometry.NiagaraRibbons=0

r.RayTracing.Geometry.NiagaraRibbons.GPU=0

r.RayTracing.Geometry.NiagaraSprites=0

r.RayTracing.Geometry.SplineMeshes=0

r.RayTracing.Geometry.Text=0

r.RayTracing.Geometry.Cable=0

r.RayTracing.Geometry.StaticMeshes.WPO=0

r.RayTracing.Geometry.NaniteProxies=0

Nothing helped

2

Hello there,

I’ve reproduced the issue, and I will report the issue as a bug.

Best regards,

Chris

3

As a note, given this is potentially limited to a subset of drivers, you may wish to investigate using the driver deny list to warn on problematic drivers.

This can be achieved by either modifying BaseHardware.ini or creating DefaultHardware.ini in your project’s Config directory.

Base Hardware contains working examples and is worth referencing.

`[GPU_AMD Windows]
SuggestedDriverVersion=“”

+DriverDenyList=(DriverDate=“<1-1-2025”, Reason=“Potentially problematic driver versions”, RHI=“D3D12”)`Please note that this is only provided as an example: I have not verified that all 2025 drivers are affects, nor have I validated that all 2024 drivers are functional. I only tested the latest 25.6.1 driver, which does exhibit the issue.

For completeness, these deny lists are also available for other vendors and platforms.

Best regards,

Chris
4

Radeon: 24.3.1 driver version didn’t have a crash. But it is 1 year downgrade, maybe we need engine modification or so? We tested almost every 2025 drivers, including Optional and they didn’t work

5

On 24.3.1 driver version, the issue is still here, but instead of crash we see the same errors in the log

[Image Removed]

6

Please find the bug report at Unreal Engine Issues and Bug Tracker (UE\-307674\).

This may be marked as a duplicate since there is already an internal ticket for the issue, but updates should be tracked on there too.

Best regards,

Chris

7

Would you mind testing 24.9.1 or 24.12.1?

No guarantee they will fix the issue here, but these should be the currently recommended drivers for Fortnite.

Best regards,

Chris

8

24.12.1 works as 24.3.1 with same errors in log

9

That’s good to know. I’ll pass that along and get back to you.

Best regards,

Chris