The project I’m working on consists of several buildings, each in their own map. They’re all loaded as streaming levels into a persistent level. For lightmass, I bake each building separately by removing all but one sublevel. I don’t hide the other levels, because baking one level with other levels hidden breaks the lighting on instanced foliage on the hidden levels.
This all works fine, except that volume samples are only kept for last baked building. I imagine that the volume samples are stored in the persistent level, instead of a per-level basis. This is rather unfortunate though, and I can imagine many others having the same problem. Is there a way around this, am I doing something wrong?