Hi,
We have a modified version of /Engine/EngineSky/M_AdvancedSkyDome applied to our sky sphere, and the SkyAtmosphereLightDiskLuminance behaves incorrectly with EffectsScalibility in Low, triggered by r.SkyAtmosphere.TransmittanceLUT.UseSmallFormat=1.
The issue is at least present on PC DX12, with on steamdeck (proton + win64), the darkened disk flickering a lot.
I suspect this is due to PF_FloatRGB vs PF_R8G8B8A8 formats, you can visualize the result with r.SkyAtmosphere.TransmittanceLUT.UseSmallFormat set to 0 or 1 in the attached images. Setting r.PostProcessing.PropagateAlpha to true doesn’t trigger the issue when UseSmallFormat is 1 so the issue might come from PF_R8G8B8A8, not entirely sure.
Thanks in advance,
Hugo
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Hello,
Thank you for reaching out.
I’ve been assigned this issue, and we will be looking into this visual difference for you.
We have not been able to reproduce the sun disk visibly changing based on r.SkyAtmosphere.TransmittanceLUT.UseSmallFormat.
Can you please send us a minimal test project that demonstrates this, and include screenshots of the issue from that test project?
The guide for test projects:
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Hi Stephen,
Please find attached an image of how to repro (showing only modified properties), this is in a simple separate project we have, the issue appears with the directional light with that specific rotation, and sky atmosphere Rayleigh / Mie settings. You should be able to see that tweaking rayleigh scattering changes how “cut” the disk appears. As you can see I managed to repro on the sky sphere when it uses M_SimpleSkyDome engine material.
Best,
Hugo
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Hello,
Thank you for reporting this. I can confirm this issue can be reproduced as described in the latest CL, and have opened a bug report:
https://issues.unrealengine.com/issue/UE\-372110
The tracker will be visible after it is approved internally at Epic Games and is publicly accessible.
If you have any further questions, please let us know.
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