Strange issue with meshes

Hello. I am experienced strange issue.
When I firstly import the scene from datasmith and I havent touched yet the light settings ( to kill the menanigless autoexposure ) - everything seems fine, and there were not this strange frangments. Once I’ve set the lights to static and prevented autoexposure -the waterfall of errors followed and this as result:

My questions is :

  1. Why this happens ?
  2. How to fix it ?


  1. When you place new mesh(es) into a scene they get dynamic lighting, this is what you see in the beginning
  2. There are 2 options: either your mesh is badly modeled and has overlapping polygons or flat areas split up into smaller areas as seen on your screenshot (I think this is the case) and/or the lightmap for the mesh is laid badly and/or has overlapping islands…

Wherever you have a “cut” on your lightmap, it’s very likely you’ll discover lighting problems… It’s a map with the lighting information! For example if you separate a flat area into 2 islands diagonally then Unreal will treat them as 2 separate areas and calculate the lighting like so…

Could you show us a wireframe screenshot of this problematic mesh and also its lightmap?

It is just an export from Revit to Twinmotion and then to Unreal. How I am supposed to fix this in such scenario ?

Maybe it is a bug into the importer ? Should I post it into bug section of Twinmotion to Unreal ?