A very important decision you will need to make is whether you would like the Axes of your World to be endless or fixed. Fortunately, you can choose a separate option for each axis on your World!
A Fixed Axis has a set boundary. If a World Region load operation or external source attempts to add a user for a World Cell that sits beyond this boundary, the Add User requests is ignored. The result is that the Streamable Grid has only a single set of Cells present on the axis.
An Endless Axis has no set boundary, and World Region load operations or external sources are able to add users for World Cells that sit beyond the axis boundary of the Streamable Grid. Whenever a World Cell beyond the original Streamable Grid's boundary needs to be loaded, the World loads the equivalent World Cell from the fixed portion of the Streamable Grid. Put another way, all Cells on the Streamable Grid for the given axis are repeated in both directions. The effect is repeated each time the player gets close to the boundary of the current Streamable Grid representation, which is where the endless term comes from. This creates the illusion of a spherical world, because the Player is able to travel continuously in a single direction with the World repeating itself over and over again.
When using an endless axis, you can identify whether a World Cell is a part of the original fixed portion of the Streamable Grid or whether it is part of a "repeated" Streamable Grid by using its CellOnEndlessGrid property. The value of this property will match the value of the World Cell's CellOnStreamableGrid property only when the World Cell has not been repeated.
When referencing World Cells and/or storing them in key based collections, you must always use the CellOnEndlessGrid to identify the World Cell. This is because multiple World Cell's with the same CellOnStreamableGrid value may be loaded at the same time, but each World Cell will always have a unique CellOnEndlessGrid value!
The Use Endless Layers option is only used if the Base World Grouping is using a Streamable Grid with Three Dimensional Axes. This is because all Groupings must be 3D in order to have repeating endless Layers. If a Sub Grouping is 3D but the Base Grouping is not 3D, the Sub Grouping's Layers will not be endless, even if Use Endless Layers is enabled.