Lumen Explained - important tips for Unreal Engine 5

While lumen is fairly user friendly and works very well out of the box there are several changes to the way you need to make your models and materials look good. By default Lumen is active and you don't need to change anything but in the event that you've migrated a ue4 project over to ue5, you need to enable it.

Lumen achieves real-time indirect lighting with rather surprising accuracy, the emissive lighting does contribute to GI (global illumination). So if you have a large bright material it will light up your scene. Lumen also provides reflections and integrates GI into the reflections. Lumen also supports clear coat materials properly and fully shadowed skylight. It provides a dynamic GI and sky shadowing on translucency and volumetric fog. The most of the heavy lifting is done under the hood. If you're going to use Lumen with any high poly assets they pretty much need to be nanite if you want good frame rates. You need to remeember that only simple meshes and interiors can be supported - you can't simply just use one large combined mesh for an interior. The walls, floors and ceilings need to be separate individual models. More useful info in the video.