Effect: Physics - JavaFX Special Effects - page 116

Figure 6-1 shows a ball that is above two walls. When the application is run, the ball will fall and
bounce off the top wall first, then the bottom wall. To understand how this animation works, consider
the variable worldUpdater in Main.fx. This variable is of type Timeline and is used to drive the animation;
it does this by calling the function update 30 times a second. The function update does two things—first it
asks the world object to advance the location of all of the bodies by one step, then it asks each WorldNode
to update itself based on any changes to their associated bodies .
Listing 6-2 illustrates how bodies in the world drive nodes in the scene .
Listing 6-2. WorldNode.fx
public mixin class WorldNode {
public var bodies:Body[];
public var joints:Joint[];
public abstract function update():Void;
}
Listing 6-3. Ball.fx
var lighting = Lighting {
light: DistantLight { azimuth: -135 elevation: 85 }
surfaceScale: 5
}
public class Ball extends Group, WorldNode{
public var radius = 10.0;
var arcs = Group{};
init{
var arc1 = Arc{
radiusX: radius
radiusY: radius
startAngle: 0;
length: 180
fill: Color.WHITE
}
var arc2 = Arc{
radiusX: radius
radiusY: radius
startAngle: 180;
length: 180
fill: Color.BLUE
}
insert arc2 into arcs.content;
insert arc1 into arcs.content;
effect = lighting;
bodies[0] = new Body(new net.phys2d.raw.shapes.Circle(radius), radius);
bodies[0].setPosition(translateX, translateY);