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Lighting Artifacts with Caves and Movable Lights

I have a cave mesh that is being lit by a movable light from outside but inside the cave, the light creates weird artifacts.
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The light creates these weird highlights throughout the mesh as well as anytime geometry clips through it (as seen with the stalactites and rock)
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A workaround I’ve found has been to change the SkyLight Source Light intensity down to 0, which fixes the issues but unfortunately makes everything else dark. The cave is a single-sided static mesh that’s being lit and shadowed as two-sided. Any help on either how the mesh or light should be set up to accomodate this would be great.

There’s a Shadow Bias setting which will make shadows stick closer to the objects casting them (which is causing your bleeding issue) but it can also introduce some line artifacts in the shadows. It would be best to place something outside of the cave to block the light from going inside.

Unreal engine has had a bug for over a year in which the normals of a mesh will be lit from the opposite side if using a directional light. I have posted about this bug numerous times, but despite reported it doesn’t seem to have ever gotten a fix. People just seem to always suggest adding extra mesh around the outside to block the light

EDIT: The bug report can be originally found reported HERE

and here is the link to the bug tracker page, which lists it as unresolved. Happens with any surface that does not have additional polygons blocking the light, seemingly making the “two sided” attribute useless.

Please upvote this bug so it gets addressed

As you can see hereit is still present in 4.12