Hello,
We’ve encountered an issue related to Global Illumination that seems to occur primarily on machines with mid-range GPUs (e.g., RTX 3060, 3070). The problem is reproducible in packed game when first entering Play mode or when remaining idle in the level. In these cases, the scene becomes darker.
Interestingly, adjusting the Global Illumination quality to any different value during runtime immediately corrects the lighting, restoring it to the expected appearance.
We would like to understand what might be causing this behavior, and whether there are specific settings or configurations we can adjust to avoid it.
We’ve attached screenshots showing both the correct and broken lighting states for your reference.
Best regards,
Harut
Update:
We’ve observed that the issue occurs on all types of devices when the Global Illumination quality is set to Low.
Hello [mention removed]
Thank you for your response!
I’d like to reiterate our latest observation: the issue is reproducible on all types of devices, including high-end GPUs such as the RTX 4090, when using Low or Medium Global Illumination settings.
It’s also important to note that we do not override any default engine scalability settings. We’re using the defaults defined in BaseScalability.ini, where for [GlobalIlluminationQuality[Content removed] as expected.
The scalability settings themselves seem to be working correctly. However, the issue arises in the following scenario:
- Using Global illumination settings as Low or Medium.
- Entering the Play mode multiple times (mostly issue occurred at the very first time), the Global Illumination can randomly become corrupted (i.e., the scene appears much darker).
- If we change the Global Illumination quality during runtime—for example, switch from Low to Epic, and then back to Low—the lighting returns to its expected state.
Please let us know if there are additional diagnostics or settings we should investigate to help figure this out.
Please find attached the video of described scenario.
Best regards,
Harut
Hello [mention removed] ,
Thank you for your response — based on your insights, we’ve made a step forward in narrowing down the issue.
Following your suggestion, we tested the scenario by manually setting the SkyLight intensity to 0, and the result perfectly matches the visual outcome seen in the original issue. (Please refer to the attached short video for reference).
This leads us to believe that, during level startup under Low or Medium Global Illumination settings, the SkyLight intensity is somehow being reset or initialized to 0.
Is this a known issue, or could there be a configuration detail we’re missing that would explain this behavior?
As a temporary workaround, we’re considering restoring the SkyLight’s intensity value manually in BeginPlay, after a short delay (need to test). However, we would greatly appreciate any guidance on a more robust or engine-recommended solution to prevent this from occurring in the first place.
Thank you again for your support!
Best regards,
Harut
Hello there,
If this also occurs on Medium, it’s potentially the cvar r.Lumen.DiffuseIndirect.Allow. Scalability 0 and 1 set this to 0.
It’s possible the 3060 and 3070 are getting assigned a lower scalability.
I haven’t managed to get a repro case that’s quite as severe as the one you show, so it may be a different issue.
Best regards,
Chris
Interesting. I’m not managing to replicate this, but without DiffuseIndirect, most of the indirect lighting contribution is likely from the SkyLight. Setting intensity to zero seems to create similar visuals to the screenshots you attached. More so than disabling DiffuseIndirect would have.
I would have imagined that the issue would be visible on all settings to an extent as SkyLight contribution isn’t replaced, but does manually disabling the skylight in editor seem to replicate the issue on Low and Medium?
Best regards,
Chris
I’ve noticed that you are using UltraDynamicSky. Would you mind testing if this issue can be reproduced with a standard SkyLight?
That may at least narrow the problem down somewhat, as I’m not encountering this issue with standard SkyLight actors changing intensity.
Best regards,
Chris