Unexpected Light Reflections with Materials (Lumen/UE5)

I encountered an issue where the material’s tiles had unexpected light bounces.

It was due to a Pixel Depth Offset (PDO) in the particular material I used.

Pixel Depth Offset (PDO) is a rendering technique in Unreal Engine that subtly adjusts the depth values of pixels to create more natural blending effects between overlapping meshes. This results in smoother transitions and a more realistic appearance, especially at the boundaries of objects.

I simply disabled PDO from the material to resolve the issue. (Make sure that it is the Material, not Material Instance)

Other Lumen-related lighting issues are listed in the official documentation.

https://dev.epicgames.com/documentation/en-us/unreal-engine/lumen-technical-details-in-unreal-engine?application_version=5.0#troubleshootingtopics

Such as

• Splotchy Artifacts seen in Mirror Reflections Indoors
• Small Meshes are Black in Mirror Reflections
• Sky Occlusion and Global Illumination Disappears at 200 Meters
• Light Leaking in Large Cave-like Areas
• Lighting Changes Propagate too Slowly to Global Illumination
• Small Emissive Meshes Do Not Light the Scene Consistently
• Wanting Highest Quality Mirror Reflections Even if Not Performant