Meshes not affecting GI. Black in Lumen Scene Vizualisation

Hi, I have an issue with lumen where meshes are not contributing to GI and they are black in the Lumen Scene view. This seems to be an issue with the mesh itself maybe coming from the export (blender). Lumen is on this is not a nanite mesh. You can see a light affecting the back wall and some circular flickering. The random cube I imported is working fine. The walls to the right and left of the light are not receiving any lighting in scene view. Any help would be greatly appreciated.

Lumen Scene Visualiser

Lumen GI Visualiser

Hello. I have a fix for this! I had this same issue and appears to be a bug with certain imported Mega Scans assets. Open up the Parent material for the mesh that is rendering black and make sure the Shading Model is set to “Default Lit”. A bunch of my imported megascans assets imported with the Shading Model set to “Cloth” by default which renders black in the Lumen Scene view and will NOT contribute to bounce lighting. I realize your scene does not use Megascans but would still advise you to check your Shading Model on each material applied to assets rendering black.

hi, thanks for the reply. The problem is my meshes are one sided polys and convex / concave meshes. In the recent lumen livestream they stated this type of interior is not supported yet. The fix is to detach all your walls and floors into single objects - it takes a bit of testing to see which objects are causing this issue. Its a real pain to work with - hopefully support is added for this in the future.

@anonymous_user_34534f1e1 - thse are all my own assets with a basic flat texture on. Not Megascans assets.

SOLUTION: You guys are going to love me. LOL. OMG bro this was driving me crazyyyyy!!! So here is the issue. When you use LUMEN SCENE VIZUALIZATION you get some black areas that are not contributing to the GI. For example for me I had a house that was built using 3Ds Max. I use the wall tool to make all the walls. Then, to make it more manageable I attached all my walls into one single object so that when I imported that into UE it was all one piece. So far so good. It imported as one huge mesh. The house was probably 200 sqm2. In unreal engine it was very manageable because I only had to worry about one big object. PROBLEM: When using the Lumen Scene Visualization some rooms had some walls completely black. I had one bathroom that had one single window and the bathroom was very dark inside using only natural light so my normal reaction was to try to increase the skylight intensity so I can try to trouble shot. I increased the directional light indirect light intensity as well in order to inject more light but that did not work. So I had to try something else. Then I started make cubes inside that bathroom and I noticed that the cubes were emitting and receiving light from lumen GI. Bingo!!! So what I did was to separate each bathroom wall back into a single object and voila!!! suddenly now those walls were receiving and emitting GI FROM LUMEN. I hit the jack pot. I separated all the walls and made them all individual objects and imported all the walls into unreal engine and my scene looked like a million dollars since now every walls was contributing to the GI. OMG it was like taking a stone off my shoe. So if you have an object that looks black when using lumen scene visualization you may have 2 issued. #1 that the normals are flipped inwards. Try that first. If you are familiar with 3Ds max you know that by selecting an object using the polygon option, if the face is inverted, it shows dark red and if the normals are correct, it will show light red. If your object has the normals facing outwards then your issue is that you have too many elements attached into one single object and that is confusing unreal engine lumen GI
SOLUTION TO THAT PROBLE. #1 create a layer. #2 Separate all you elements into a layer. #3 Select all your elements and click group. #4 Now use datasmith to import that group of objects (and the group element) into unreal engine. Unreal Engine will detect that group and will use it as an empty actor and it will put all your objects inside that empty actor making it more manageable.

I hope this helps.