Lumen - Bright Exterior, Super Dark Interior

Hey all,

I’m having some real pain trying to get Lumen working correctly. I’ve set it all up so both a directional light and skylight are lighting up the scene. On the outside of my environment it looks perfectly fine, but internally it is incredibly dark, almost as if it isn’t bouncing any light.

Does anyone have any ideas why this might be happening?


You need auto exposure. It’s enabled in projects by default.

Did you switch it off?

Hey @Bdcoll!

Additionally, are you using an HDRI dome possibly? Currently, having one (even if it does not cast shadows) may cause issues with indirect lighting aka light to not bounce in interiors.

Any additional specifics about your scene you can provide may go a long way in solving your problem.

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Unfortunately Auto Exposure is enabled

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I don’t have any HDRI Dome in the scene, but the information about it potentially causing issues is good to know.

Is their anything specific you need to know?

Has anyone else got any ideas on how to potentially fix this?

Is it on a mac? ( I’m seeing this elsewhere )

Afraid not. I’m running this on Windows 10 (I have also tried it on Windows 7 with the same results)

I did wonder if it was the original Project being in 4.27 and upgraded to 5.1. However I rebuilt the Project with the same props and lighting setup in a fresh 5.1 Project and I get the same results

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I’m seeing this is various places, but I’m not sure what’s causing it…

Could it be your mesh is one big object? If so, they wont bounce light. Read more here Lumen Technical Details in Unreal Engine | Unreal Engine 5.0 Documentation

Even in that case, at least screenspace should kick in and illuminate the scene, but even for that it looks way to dark - although there is some bouncing visible on the ceiling and the corner.

I wonder, if the glass is blocking it, or Lumen for whatever reason getting thrown off by glass and windows. There was another thread regarding glass and Lumen not working properly together:

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I’m afraid not. These are all modular pieces that i’ve thrown together to create this test scene.

You are my savior! This is exactly what was causing my problem, and the solution in that thread solved it.

Thank you very, very much!