UE5.8: Lumen Hardware Ray Tracing shows abnormal lighting and reflection results when running in the Editor on AMD 6000+ series GPUs (images attached). Is there a way to fix this issue?

Development Rendering
,
1

I tested the same project with identical project settings on two different computers.

On the AMD GPU system, when running the project in the Editor with Hardware Ray Tracing enabled, the corners of the scene become significantly darker, and the reflections also appear incorrect. However, the packaged build renders normally. The GPU used is an AMD RX 6750 XT.

On the NVIDIA GPU system, this issue does not occur.

Although this does not affect the final packaged output, I would still like to find a way to keep the lighting and reflections displaying correctly when developing on computers with different GPUs.

I could really use some help figuring this out

QQ20261006-205948
QQ20261006-2059481548×1745 288 KB

2

I recently had something related. Reflections on smooth objects were NUTS, it took me about 3 months before I stumbled across the cause.

Take a look at the Lumen scene view. Your level should look roughly the same but fuzzier.

If anything just isn’t there, or is the wrong shape, you have to find out what’s wrong with it’s distance field.

Mostly, it’s just missing, but sometimes collision needs adding to the mesh, or the DF resolution needs increasing a bit.

3

A bad distance field is unlikely here. That would be wrong on both GPUs and in the packaged game, and you already said the packaged build is fine. The Lumen scene view is still worth a look (if a mesh is missing there, fix that mesh), but it will not explain an editor-only difference on an RX 6750 XT.

The editor viewport and a cooked game do not run the same ray-tracing path. The editor view family compiles extra debug and hit-lighting permutations the packaged build often never uses. Darkened corners plus broken reflections, only in the editor, only on AMD 6000, is that class of problem rather than a content bug.

On the AMD machine, compare these in the editor console, not just the project settings:

  • r.Lumen.HardwareRayTracing
  • r.Lumen.Reflections.HardwareRayTracing
  • r.Lumen.HardwareRayTracing.LightingMode — 0 is surface cache, 1 is hit lighting. Hit lighting is the mode that goes wrong on some AMD drivers. Set it to 0 and see if the corners come back.

Then switch the editor RHI. Hardware ray tracing exists only on DX12, so if DX11 with software Lumen looks correct, you have isolated it to the HWRT shader and not the level. Note the Adrenalin version too. Those drivers have both fixed and re-broken inline ray tracing in the editor viewport, and a packaged build uses the cooked shaders plus a different denoise path, which is why shipping can look right while the viewport does not.

If you need this machine’s editor to match the NVIDIA one while you work, put r.Lumen.HardwareRayTracing=0 in a WindowsEditor override (DefaultEditor.ini or a device profile for that GPU) and leave it enabled for the game. You do not have to turn Lumen off in the project to hide an editor-only AMD viewport bug.