Pulling It All Together: Clown Cannon - JavaFX Special Effects - page 233

clownNode , and restarts the Timeline powerAnim . The Timeline powerAnim causes the value of cannonPower
to change from 0 to 1000 over 1 second. When the value of cannonPower changes, a new LinearGradient is
applied to the Node powerFill . This is what animates the power bar on the upper left of the scene.
Once readyLaunch is called, the game is ready for the user to fire the clown. When the user clicks the
mouse button or presses the spacebar, the function fireClown is called. The function fireClown stops the
Timeline powerAnim and uses the current value of cannonPower and the current value of cannonAngle to
create a new ClownBody . The class ClownBody is used to synchronize the position and rotation of the Node
clownNode with the Body that represents the clown in flight. Listing 11-5 shows the class ClownBody .
Listing 11-5. ClownBody.fx
public class ClownBody {
public-init var startingPower:Number;
public-init var clown:Node;
public var body:Body;
init{
body = new Body(new net.phys2d.raw.shapes.Circle(4), 1);
body.setPosition(clown.translateX, clown.translateY);
var rotationInRadians = Math.toRadians(clown.rotate);
var x = Math.cos(rotationInRadians) * startingPower;
var y = Math.sin(rotationInRadians) * startingPower;
body.adjustVelocity(new Vector2f(x,y));
}
public function update():Void{
clown.translateX = body.getPosition().getX();
clown.translateY = body.getPosition().getY();
var velocity = body.getVelocity();
var vX = velocity.getX();
var vY = velocity.getY();
var tanTheta = vY/vX;
var arcTan = Math.atan(tanTheta);
clown.rotate = Math.toDegrees(arcTan);
}
}
In Listing 11-5 we see that the class ClownBody does a few things. When the init function is called, a
new Body is created, and its position and rotation are set the same as the Node clown . The Body is also
given an initial velocity based on the angle of the cannon and the startingPower . The update function is
called by GameMode to synchronize the position and rotation of the Node clown based on the position and
velocity of the body . By setting the rotation of the Node clown based on the velocity of body keeps clown
pointed in the direction it is traveling.
Once the clown is prepared to fly through the scene by the function fireClown , the Timeline
worldUpdater is started, which calls the function update every 30th of a second. The function update
advances world by one step and updates the location of flyingClown . The function update also checks to
see if the clown has intercepted the balloon, if the clown has landed in the bucket, and lastly, if the clown