The following transitions fall into this category: FadeTransition, FillTransition, and StrokeTransition.

The FillTransition transition makes a smooth change between two colors:

// chapter5/transitions/ColorTransitionsDemo.java
Shape circle = new Circle(50, 150, 50);
FillTransition ft = new FillTransition(Duration.seconds(3), circle, Color.RED, Color.BLUE);
ft.play();

Intermediate values are calculated based on RGB and opacity numerical components of the Color through a special interpolator.

To make the Animation API aware of the interpolator support, the Color implements an Interpolatable interface, which you can use for your own components as well:

public interface Interpolatable<T> {
    public T interpolate(T endValue, double t);
}

The StrokeTransition transition works the same way as FillTransition but on the stroke of the Shape (the outer border; see Chapter 2, Building Blocks – Shapes, Text, and Controls).

The FadeTransition transition changes the opacity property of the Node.