Creates a new spline action with a set of points. The setter is a
callback for setting the positions, points define the spline, and
duration
is the time for the action to complete. Optionally a curve
can be used for easing.
Source
ActionSpline(this.setter, this.points, double duration, [Curve curve]) : super(duration, curve) { _dt = 1.0 / (points.length - 1.0); }