I am not fully sure if I run into a bug which obviously would make sense given the nature of this early access build but I figured I create a post about it.
I have an issue with emissive effects when using lumen to disappear based on visibility of the emissive source but only if the emissive area is just part of a mesh and not the full static mesh.
So I have this Fish tank for example and in the top of it is a part that is emissive shining down into the tank. That fully works! when I am in front of it with my camera it looks great. But when the emissive part is invisible to the camera by going a bit back or moving the camera up while still looking in the direction of the tank the emissive effect disappears.
So I figured okay this is probably a limitation of lumen. But when I for example have an object and make that completely emissive and place it on one side of a wall and go to the other side I can see see the spill of the missive area creeping around the corner and illuminating everything.
So I am not quite sure why those two basically very similar scenarios react so differently.
From my quick testing the contribution from occluded objects to Lumen stops at about 9m. If you can see the emissive object then it continues to contribute for 1 km I think. It appears that after 9m the amount an emissive contributes to Lumen is directly dependent on the amount of the object in view. You can test this easily in Editor, place an emissive object on an a floor and position the camera 2m above it now move the camera to the side till the emissive object is off screen. The amount of contribution to Lumen doesn’t change much overall. Now repeat the same thing but 10m above the emissive object, as soon as part of the object goes out of view the contribution to Lumen starts to drop until the object is off screen and contribute nothing. I also get the same results sliding an object in front of an emissive rather than moving the camera. I tried increasing the bounds of the emissive object in case it was simple occlusion culling but that made no difference. Hopefully the Lumen live stream next week will have some more answers.
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