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4.14: Light Bleed and Light Flashes/Flicker Render Issue

I've been having an issue with light bleed and a strange light flashing in my game. Even on production quality light builds I still get this issue.

The assets I am using are from a paid pack called "Modular Sewer Set" and cost £9 (I definitely recommend this set). But the point is, I don't have experience in lightmaps and texturing so I cannot change anything to do with the assets myself unfortunately.

Here's a video I recorded of both of my problems: https://www.youtube.com/watch?v=IoVjwTTZkKg

Thanks, Tom.

So the light bleed is self-explanatory as it is a common issue, but here is what the light flash looks like: Light Flash Issue

It's almost as if it's showing me the sky through the walls.

EDIT: Images.

Product Version: UE 4.14
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asked Jan 25 '17 at 07:35 PM in Rendering

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avatar image Krilium Jan 25 '17 at 11:21 PM

Fixed the Bleeding issue by deleting the skylight, but keeping the directional (sun) light. The world is a lot darker but I can get away with it because the game is set indoors with occasional small openings on the roof. But I still have the flickering/flashing issue.

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This one actually comes up often and is reported as a bug but it's all working as intended. I made a video a long time ago that covers some things you can do on your end: https://youtu.be/6MhsdwTW3SQ

Ultimately, what you're seeing here is caused by Dynamic Occlusion Queries. This means that anything that is occluded by another actor in the world is not rendered behind it. The GPU has to do a check to see when something should be rendered vs not rendered. This check has to be sent to the GPU and then read back one frame later, which causes the "pop/flash" that you see. The video above details some steps you can take to alleviate this. It comes down to design for your project and using alternative methods for culling. The culling methods in UE4 should all be used in conjunction with one another instead of relying only on GPU queries. This removes some of the overhead of having to check the actors visibility state on the GPU every frame.

I hope this helps you.


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answered Jan 26 '17 at 05:43 PM

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Tim Hobson ♦♦ STAFF
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avatar image Beregron Jan 30 '18 at 08:55 AM

Hi Tim,

i postet 10 minutes ago. And i have the same Problem with my Project. I came across your answer. Is this bug fixed? I can't get the Pop/Flash go away. But i can't record it, because in my fraps Videos the light Flash is not seen.

avatar image Beregron Jan 30 '18 at 08:57 AM

I will try your answer in the Video again. I hope this works.

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