In SealEngine, the frame images of a billboard instance are PNG files in
the archive, named "<name>\<basename>.png", "<name>\<basename>[1].png"
and so on, and the motion frame number is the index into them.
This also changes the lifetime management for billboard motions. A
billboard's motion holds the frame animation state of the instance,
which the game sets up before calling Load, so keep it across loads
and free it in free_instance.
kichikuou
5cc163ab16