UE5.5 illumination

Development Rendering
,
2

Hi @Homes_Lu! This lighting inconsistency is often caused by differences in normals, smoothing groups, or lightmap UVs, even if the material and lighting setup are identical.

Here’s what you can try:

  1. Check smoothing groups and normals in 3ds Max apply a “Normal” modifier or unify smoothing before exporting.
  2. In Unreal, verify if both meshes have valid lightmap UVs (Channel 1) and matching tangent space.
  3. Ensure both parts have the same scale/transform and Nanite settings, as differences can affect shading.
  4. Try combining both parts into a single mesh in Max and export again to see if the issue goes away.

I am leaving you some documentation that may be helpful.

https://dev.epicgames.com/documentation/en-us/unreal-engine/lighting-the-environment-in-unreal-engine?application_version=5.0#lightmapuvs

If you’re still facing challenges or have new questions, feel free to share.