Lumen seems to work perfectly fine for everyone, except for when I try to play with it 
I just keep getting weird results no matter what I try…
This time I keep getting these weird poppings of the light and reflections (gif below).
Looks like it is based on the camera/view rotation but I am not sure how to fix it. Any help would be appreciated. Thanks!
Check the lumen scene view under lit. Make sure you have distance fields enabled on all your static mesh, separate walls/floors/ceilings into separate and simple meshes. Make sure walls are at least 10 cm thick.
Thanks for the help, I checked the models and they are not 10 cm thick. These are modular pieces combined together with no thickness. That’s a bummer, I hope there is a workaround for this problem.
There are, fortunately.
Without getting to complex, what you’re seeing are the screen-space reflections and global illumination component of lumen, which is creating view-dependant lighting because the backup global illumination features are either not working or disabled.
If using software lumen, models need a minimum thickness because the static meshes themselves aren’t actually being used in the lighting: rather, a signed distance field, a sort of blobby representation of them stored in a volume texture, is. They need to be 10cm or thicker because if features are too thin, the volume texture won’t store them. The workaround for this is to go into the mesh’s settings and adjust the ‘distance field resolution scale’ higher. Get in the mesh distance fields viewmode, start with 1.1 and keep going higher until you see the features start to become visible.
If you have an RTX card that supports hardware ray-tracing, then you have a much easier solution: enable HWRT, and meshes of arbitrary dimension can be represented because lumen is tracing against the triangles themselves (sort of, technically a proxy mesh but that’s splitting hairs). Make sure your target platform is Dx12, enable hardware ray-tracing, and tell lumen to use hardware ray-tracing when available, and that should solve your problem.
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Thanks alot for the informative explanation, helped me understand more about Lumen!
From my frustration I decided to block out the outside of the house using the basic cube, not sure if that was a smart fix but it worked haha. I will definitely try the stuff you wrote, thanks again!
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That’s actually a pretty good strategy for dealing with SWRT problems, I did the same thing in early access before hardware ray-tracing was more mature than it is now. Basic cubes with the albedo tinted a single color roughly matching the real wall have yielded better results than you think.
And I was happy to, thank you for the gratitude though. Lumen is a complicated, hairy beast of a program, and even the documentation Epic currently has isn’t that deep compared to all of the features and complexities buried under CVars. I wish the best of luck with your project!
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