Why Rect lights turn into Point lights after reducing attenuation radius? And what causes ghosting?

[ZsLaboratories (Zainab Al-Ansari)]

We’re having weird problems working on an interiors project on one of our machines.

If you can see from the screenshots, when reducing attenuation radius of a Rect light its icon turns into a Point light, but also we get flickering issue in the editor for only Rect lights. And there’s this weird “ghosting” effect happening.

This started happening relatively recently, and it’s even happening on older 5.2 projects that never had this issue which we worked on last year.

We’ve tested the same projects on 3 other machines than the problematic one, none is showing this erratic behavior.

The problematic machine is windows 11 and has rtx 4090, the non-problematic ones:
a Window 10 with a 3090, a Windows 10 with 4090, and a Windows 11 with a 3090

We suspected that maybe the graphics card driver for 4090 on Windows 11 is causing the problem so we reverted to an older version from May but it’s still happening.

Any pointers what might be causing this would be much appreciated.

Note*: this machine was originally Windows 10 but it got automatically updated to Windows 11 around 5 months ago in Feb 2024

Edit 20th August: Now issue happening on other machines also

[Arkiras]

@ZsLaboratories

If you can see from the screenshots, when reducing attenuation radius of a Rect light its icon turns into a Point light

Lights will only cast light within their attenuation radius and you have set that radius smaller than the area of the light, so the light only extends to the attenuation radius, making it basically behave similar to a point light.

@ZsLaboratories

This is an nvidia display driver bug, there are many threads about it here but most people resolve it by rolling back to an earlier version.

[ZsLaboratories (Zainab Al-Ansari)]

Thank you so much Arkiras, didn’t know that about the light!

I did roll back the driver and didn’t fix, I’ll try again with even older and see if it’ll be ok