I have a question. But first I have a related World Building solution that I could not find elsewhere. I tried using the Merge feature from one project that was used to build the sub-level, Merged over into the main project Persistent level using the merge feature from the sub-level project. I don’t recall the exact steps to failure. But basically the process ends up not producing a parent root node for the sub-level inside of the Outliner. Then there is no way to act on the level as a whole. And as a result, translations, rotations and scaling then affect the individual sub-parts of the level, rather than affecting the level as a whole unit. I tried groups, but they don’t seem to allow the sub-level to be adjusted into position as a whole.
The solution that I found is to, instead: drag and drop the Level from the Content Browser into the parent Persistent level. This method creates the parent root node in the Outliner. Then selecting the root node in the Outliner, in Details, the translation, rotation and scaling can be set for the level and where all of the sub-parts for the level act as I would have expected.
I also found that it was best to figure out what the translation, rotation and scaling need to be using a simple shape (eg. a cube or a plane). Then to write down the translation, rotation and scaling for the cube. Then after dropping the sub-level into the Persistent level, and after selecting the sub-level root node in the Outliner. Then in the Details section, to manually enter the translation, rotation and scaling numbers. This avoids multiple lengthy Build Navigation recomputations for each small adjustment that is made in the viewport.
Thereafter, to add the sub-level to the Levels Tab using Levels drop down and Add Existing option. And then selecting the sub-level file. Which then creates the sub-level relationship in the Levels tree beneath the parent Persistent Levels node. Also (optionally) setting Levels Tab > Sub-Level > Right click > Change Streaming Method > Always Loaded.
So now that the sub-level is in the parent Persistent node. The problem that I am still having is that when a character transitions from the main Persistent Level into the sub-level, there is a conflict between the lighting in the sub-level and the Persistent level. Either the two lighting sets amplify and blow out the scene with too much light. Or one or the other of the two levels gets no light at all.
I have read a number of posts and papers that describe a number of methods to resolve this problem. But so far, none of them have worked as I would expect.
At best, when the character transitions into the sub-level, for a short distance into the sub-level (like 1 foot in), the light begins to fade quickly. Then beyond a foot or so in to the sub-level, the viewport goes completely black.
Since the parent Persistent level has a bunch of features (landscape, etc) in the level. The suggestion that the Persistent level should have no lighting at all, is no longer a practical solution.
I was wondering if anyone knows the specific settings and such necessary to have the parent light pass into the sub-level. Or that allows the sub-level to have it’s own lighting that then does not amplify the parent levels lighting?
I thought maybe I could toggle the lighting during the transition, but then I would guess that might not work well for multiplayer situations. The other ideas, that I have not been able to get working, although some sound promising, the implementation details are illusive.