Why does a Directional Light illuminate surfaces inside a completely sealed Static Mesh enclosure in a stock UE5.8 First Person/Lumen project?
The enclosure consists entirely of imported 20 cm-thick closed Static Meshes with Cast Shadows enabled. Floor and ceiling use the same mesh. Directional Light Cast Shadows is enabled.
With the Directional Light disabled, the enclosure is completely black even with the Skylight enabled.
With the Directional Light enabled, the enclosure is visibly illuminated even when the Skylight is disabled and Directional Light Indirect Lighting Intensity is set to zero.
Switching between Virtual Shadow Maps and Shadow Maps makes essentially no difference.
What basic UE5.8 setting or workflow am I missing?