Exterior movable lighting with multiple static interior sublevels. Problem with volumetric lightmap.

[dc-null]

I have large exterior world that is currently using a movable directional light and skylight. That’s all working great and looks fine.

Then I have a few small interior scenes that are being lit by mostly static lights, nice bakes, etc. Again, that’s all working great and looks good.

Problem comes in when trying to add more than one of those interior sublevels to the main map.
It appears that the baked volumetric lightmap (or lightmass importance volume) gets chosen somewhat randomly from one of the interiors, instead of using all or blending them together.
The exterior directional light also appears to leak into the interior and/or ignore the shadow casting from the meshes surrounding the exterior.

So, do I need to only stream in 1 interior at a time, or does the exterior need its lighting baked (currently set to force no compute) with all interior maps loaded, so that the full lightmass bound gets baked?

[Arkiras]

From the VLM documentation:

Level Streaming requires that all levels (the Persistent and any sub-levels) all be built at the same time, otherwise streamed in levels will not be registered correctly. Streaming levels are primarily a memory optimization where the most detailed bricks volumes are merged into a bigger volume that is a cube (equal dimensional sides) instead of a box (different dimensional sides). The most detailed bricks are streamed with the closest sub-level and higher level bricks are always persistent. In levels that contain actual geometry, the majority of data goes into the most detailed level bricks. There should be little concern given to parts of the volume that appear to be empty (or “wasted”) space if the level is filled with geometry. The current system uses a single volume texture, meaning that we can’t do much about empty space since we don’t support multiple volume textures that has overlap and blending.

So my guess would be that you need to bake it with the exterior.

Not sure about the directional light leaking. Perhaps the exterior geometry is being unloaded but since the light remains, it just shines through the backfaces of your interior geometry.

[dc-null]

Yeah, i saw that, just seems like i’m missing something. The bigger the world gets (and the more spread out the baked interiors are) the worse the bake times and quality are going to get because of having to bake them altogether like that.

We are currently using lighting channels to avoid the light leaking issue though, seems like the easiest route. It is strange that its needed though.

[Arkiras]

Yeah… I wish I had a better solution to offer

Personally my hope was that GPU lightmass would help alleviate this issue, but apparently it is limited to 128 lights (according to somebody in the GPU LM thread) which is certainly not enough for a decent sized world.

If you’re willing to accept a loss in quality you can switch from volumetric lightmaps to sparse volume lighting samples