splitAtZ
Splits the current Box into two smaller boxes along the z-axis at the specified position. If the provided z position lies outside the z-range of the current Box, the method returns a list containing only the original Box.
Return
A list of two Boxes resulting from the split operation if the z-coordinate is within range, or a singleton list containing the original Box if the split cannot be performed.
Parameters
z
The z-coordinate at which the Box should be split.