unreal-lighting

Add a Directional Light, Sky Atmosphere, and Sky Light, enable Atmosphere Sun Light, and set the Directional Light in Lux with roughly 120,000 lux as a documented zenith sun starting point. Lock Manual exposure first, then enable bounded auto exposure after the noon reference is stable.

Black Lumen interiors usually indicate missing Surface Cache or Card coverage, or meshes that are too complex or incorrectly scaled. Inspect the Lumen Surface Cache visualization, split overly complex meshes, and verify mesh distance fields are generated.

MegaLights Directional Light support is disabled by default and has documented quality limitations; Epic recommends Deferred Lighting with Virtual Shadow Maps for a strong sun. Enable r.MegaLights.DirectionalLights 1 only after target testing, such as for a dim soft moonlight.

Clamp the Min/Max EV100 range so the camera cannot adapt the night back to daytime, or use equal Min/Max values to disable adaptation entirely. Reduce broad environment contribution instead of crushing blacks with post-process color.

MegaLights has fixed sampling, so too many overlapping important lights per pixel causes noise, blur, and temporal ghosting. Narrow attenuation bounds, merge small emitters, and reduce local light complexity rather than adding more lights.

Use Lux for Directional Lights, cd/m² for Sky Light luminance, and Candela or Lumens for Point, Spot, and Rect Lights when inverse-square falloff is enabled. Never prescribe an intensity number without light type, exposure, distance, source size, and target platform context.