Applying Physics to a Moving Ball

To apply physics formulas to a moving circle in JavaFX, you’ll want to simulate the motion by updating the circle’s position based on velocity and acceleration.

Apply physics: Use variables for position, velocity, and acceleration, then update the circle’s position in a timeline or animation loop.

Example

Here’s a simple example that demonstrates how to create a moving circle using JavaFX.

import javafx.animation.Animation;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.stage.Stage;
import javafx.util.Duration;

public class MovingCircleApp extends Application {

    private double x = 100;      // Initial x position
    private double y = 100;      // Initial y position
    private double velocityX = 2; // Velocity in x direction
    private double velocityY = 1; // Velocity in y direction
    private double accelerationX = 0; // Acceleration in x direction
    private double accelerationY = 0; // Acceleration in y direction

    @Override
    public void start(Stage primaryStage) {
        Circle circle = new Circle(20, Color.BLUE); // Create a circle with radius 20
        circle.setCenterX(x);
        circle.setCenterY(y);

        Pane pane = new Pane(circle);
        Scene scene = new Scene(pane, 400, 400);

        primaryStage.setTitle("Moving Circle");
        primaryStage.setScene(scene);
        primaryStage.show();

        // Create a timeline to update the circle's position
        Timeline timeline = new Timeline(new KeyFrame(Duration.millis(16), e -> update(circle)));
        timeline.setCycleCount(Animation.INDEFINITE);
        timeline.play();
    }

    private void update(Circle circle) {
        // Update velocity based on acceleration
        velocityX += accelerationX;
        velocityY += accelerationY;

        // Update position based on velocity
        x += velocityX;
        y += velocityY;

        // Update the circle's position
        circle.setCenterX(x);
        circle.setCenterY(y);

        // Simple boundary collision detection
        if (x < 0 || x > 400) {
            velocityX *= -1; // Reverse direction on x collision
        }
        if (y < 0 || y > 400) {
            velocityY *= -1; // Reverse direction on y collision
        }
    }

    public static void main(String[] args) {
        launch(args);
    }
}

Explanation

1. Timeline animation: A Timeline is set up to update the circle’s position approximately every 16 milliseconds (about 60 FPS).

2. Physics update logic:

   • The velocity is updated based on any defined acceleration.
   • The position is updated based on the current velocity.
   • Simple boundary detection is used to reverse the direction of the circle when it hits the edges of the pane.

Customization

• You can adjust velocityX and velocityY to change the initial movement speed.
• To add more complex physics (like gravity), modify the acceleration variables accordingly.
• You can also add user controls to change direction or speed dynamically.