When the IlvTiledLayer is set to free mode (or its
associated IlvTileController), the structure is not a
grid (unlike indexed mode described in Structure of the tiling grid (indexed mode
only)), but a list of rectangular areas that must be added to the
IlvTileController.
Tiled layer in free mode
These areas can have any bounds and can even
overlap.
The size of the tiled layer is simply the
union of all tile bounds.