In apt.dat terminology, a split vertex is any vertex of a
polygon where the control handles on either side of the vertex
are not exact mirror images. (When there is only one control
handle it is therefore by definition split!) You need a split
bezier any time you want to: - Have a sharp corner between two
curves and control the tangents of the curves or - Have a sharp
corner between a truly straight segment and control the curve of
the next segment. Split Beziers and apt.adt Now here's the rub:
the apt.dat format does not allow for split beziers - each
curved point has only one control handle - the other is
calculated by x-plane by mirroring...thus no vertex can ever be
split. (This is due to a total lack of brains on my part when
working on the apt.dat format, which is quite embarrassing
considering how long I spent thinking about it.) There is a way
to simulate a split bezier: if you use zero-length segments
(that is, multiple points on top of each other), you can create
a shape that works as if it is split