Like a layer, a sublevel (or subgame) is a persistent grouping of game objects. As you work in the Design View, you might find it convenient to show or hide sublevels as one way to display or hide groups of objects quickly.
Unlike layers, however, sublevels are game objects, and they do appear in the Project Lister, as shown in the figure below. In the figure, the main game level is at the top of the project hierarchy (the Game node), and four sublevels are shown, HillsideBuilding, OfficeBuildingPlaza, TerrainObjects, and Airstrip. A single game world can be divided into many sublevels.
Each sublevel is a separate LVL file; your main game LVL file includes a reference to each of the sublevel LVL files. Thus, you can work on sublevels independently of the main game level, as needed, or share sublevel files with other designers to create a large game world in parallel. Or, you can use the sublevels to partition the game world into more easily managed sections that you can show or hide as needed.
Because the sublevels are separate LVL files, you can dynamically resolve (render in the Design View) them in the main game level, include or exclude them in the main game level, or simply load them outside of the main game level and work on them separately. When a sublevel is included and resolved in the main game level, you work with it in the same way as the main game level, adding or modifying game objects as desired.
For a demonstration of how to use sublevels, view the “Using Sublevels” video, either on the GitHub site or on SHIP.
You can add new game objects to a sublevel by performing either of the following tasks:
When you save a game level that includes sublevels, any changes to the sublevels are saved at the same time as the main level. If you do not want to accidentally modify objects in a sublevel, you can lock the objects.
By default, all sublevels are automatically resolved when you open a main game level. You can use the Preferences dialog to specify that subdocuments are not automatically resolved: select the Edit > Preferences menu item to open the Preferences dialog. Select Documents, and then select Resolve on load, as shown in the figure below. If you specify Resolve on load as False, sublevels are not automatically resolved when you open a main game level. You can selectively resolve referenced sublevels as needed.