You’re welcome. I’m not sure yet, though it sounds close to the solution. Another potential cause is the volumetric lightmap (VLM) settings. Change those by decreasing Detail Cell Size and increasing Maximum Memory to get finer detail with more memory allotted for each VLM cell so it doesn’t cull too much of the outer cells. The VLM generates 3D cells, similar to voxels (like a pixel but 3D or cubic unit in 3D space), composed of lighting sample points at the corners of the cells. The default Detail Cell Size is 200, in Unreal units, which is kinda large, so decreasing the size brings those cells down to a smaller scale in the whole VLM grid. Hence, there’s more light sampling points, which requires more memory per cell (Maximum Brick Memory). High-density bricks at the periphery of the higher-density areas near surfaces are discarded until Maximum Memory limit is met. If the memory isn’t high enough, it results in inconsistent lighting and shadowing, especially near / on surfaces like the walls. Here is the page for VLM:
It supposedly increases build times to modify the settings extensively, yet I wouldn’t worry about it unless the values are extreme (like Detail Cell Size 2, and Max Memory 500 or 1,000). One other note, I think it has to have a Lightmass Importance Volume to function completely. VLM can be visualized under Show button > Visualize > Volume Lighting Samples (shows distribution of light sampling points in the Lightmass Importance Volume). Might help to visualize the Importance Volume too, which is under Show > Volumes.
As for the distance field generation of the floor, it could be due to GI or other light settings. I’m thinking the mesh distance field of the floor (the newly generated one) at a low resolution (0.2) isn’t influenced by the HDRI backdrop as much as the shadows are without the distance field. What are the mobility settings of major lights in the scene (not spot/point lights, but only directional and skylight)? If there’s stationary lights it could be a part of the issue, though doesn’t mean stationary can’t be used, rather modified somehow to get it working. Stationary lights have distance field shadowmaps calculated by Lightmass, which don’t function well for area shadowing (soft shadows based on distance from object to shadow receiver and light source angle/size). There’s a few other things, but I’ll reply to your next post with it.