This demo shows how the key field may be used to vary the speed of travel along a TCB interpolator curve.

Each of the cubes uses the same 3 keyframe values for position (stored in the keyValue field). The three cubes are stacked so that they may be easily discerned from each other.

All 3 cubes start and end their animations at the same time. The key values specify that:
-- the bottom cube reach the middle location after 1/4 of the time has passed.
-- the middle cube reach the middle location after 1/2 of the time has passed.
-- the top cube reach the middle location after 3/4 of the time has passed.