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Black DFAO/Shadow artifacts

I love the soft shadowing effect of DF shadows for my dynamic lights, but I'm having a ton of trouble getting rid of artifacts.

In my lighting test map, I have a small house that I've imported several ways - as a single mesh, as several meshes (broken down by room), as modular pieces. I've been playing with the lighting to see how I can get the best result, mostly dealing with light leaks through walls and DF artifacts.

Importing the entire house as a single mesh, the DF meshes are a mess, even with increased resolution, missing entire pieces of geometry. This is improved by splitting the mesh up into smaller pieces, but then I get nasty black artifacts at certain points where two or more meshes are close together.

For example, in this corner the interior wall and exterior wall are separate static meshes. The wall is 20cm thick. The point light is using DF shadowing. Mesh DF resolutions are increased until there's no visible result from increasing them further.

alt text

Here's the same view with DF meshes visualized:

alt text

And again with DFAO visualized:

alt text

And here's the exterior mesh (directly on the other side of the wall). The point light is casting DF shadows.

alt text

I'm also seeing similar black artifacts elsewhere where separate meshes are near each other (like where the roof meets the exterior sides.

How can I get rid of these artifacts? Is it an issue with the meshes, the way they're aligned/spaced, or is it a fundamental issue with DF shadows that I can't avoid (and should therefore just go with regular shadow maps)? Increasing DF offset helps slightly (but still doesn't produce an acceptable result), but creates leaks.

Thanks in advance for the help!

Product Version: UE 4.16
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asked Jun 10 '17 at 06:41 PM in Rendering

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avatar image Haoris Jul 22 '17 at 04:30 AM

I have the same problem. I've read a lot of post about this problem but never seen an answer from Epic

The artifact: alt text

Same image with DFAO occlusion tint changed to red (note that the artifact is still black): alt text

But the artifact clearly comes from DFAO. Same image without DFAO: alt text

sans titre.jpg (63.5 kB)
sans titre2.jpg (76.9 kB)
sans titre3.jpg (61.9 kB)
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Try using "Two-Sided Distance Field Generation" inside of the meshs settings. That appears to fix the issue for me in most cases when I am using a one-sided model.

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answered Sep 02 '17 at 10:28 PM

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avatar image Meowstopher Sep 08 '17 at 07:20 AM

This works! Doesn't seem like it should be the correct solution, but I'm not going to argue with a functional solution.

Thanks for the tip!

EDIT: Upon further investigation, this caused other issues. It seems that making the DF texture double sided significantly decreased the texture space available to visible parts, so there are many other artifacts now. It fixed up the one shown above, but caused other problems.

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