JAVA - Projectile Ball - Parabolic Path

 

package projectileshootertest;

import java.awt.BorderLayout;

import java.awt.Color;

import java.awt.Graphics;

import java.awt.Graphics2D;

import java.awt.GridLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.awt.geom.AffineTransform;

import java.awt.geom.Point2D;

import javax.swing.JButton;

import javax.swing.JComponent;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JPanel;

import javax.swing.JSlider;

import javax.swing.SwingUtilities;

public class ProjectileShooterTest

{

    public static void main(String[] args)

    {

        SwingUtilities.invokeLater(new Runnable()

        {

            @Override

            public void run()

            {

                createAndShowGUI();

            }

        });

    }

    private static void createAndShowGUI()

    {

        JFrame f = new JFrame();

        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        f.setSize(600,600);

        final ProjectileShooter projectileShooter = 

            new ProjectileShooter();

        ProjectileShooterPanel projectileShooterPanel = 

            new ProjectileShooterPanel(projectileShooter);

        projectileShooter.setPaintingComponent(projectileShooterPanel);

        JPanel controlPanel = new JPanel(new GridLayout(1,0));

        controlPanel.add(new JLabel("Angle"));

        final JSlider angleSlider = new JSlider(0, 90, 45);

        controlPanel.add(angleSlider);

        controlPanel.add(new JLabel("Power"));

        final JSlider powerSlider = new JSlider(0, 100, 50);

        controlPanel.add(powerSlider);

        JButton shootButton = new JButton("Shoot");

        shootButton.addActionListener(new ActionListener()

        {

            @Override

            public void actionPerformed(ActionEvent e)

            {

                int angleDeg = angleSlider.getValue();

                int power = powerSlider.getValue();

                projectileShooter.setAngle(Math.toRadians(angleDeg));

                projectileShooter.setPower(power);

                projectileShooter.shoot();

            }

        });

        controlPanel.add(shootButton);

        f.getContentPane().setLayout(new BorderLayout());

        f.getContentPane().add(controlPanel, BorderLayout.NORTH);

        f.getContentPane().add(projectileShooterPanel, BorderLayout.CENTER);

        f.setVisible(true);

    }

}

class ProjectileShooter

{

    private double angleRad = Math.toRadians(45);

    private double power = 50;

    private Projectile projectile;

    private JComponent paintingComponent;

    void setPaintingComponent(JComponent paintingComponent)

    {

        this.paintingComponent = paintingComponent;

    }

    void setAngle(double angleRad)

    {

        this.angleRad = angleRad;

    }

    void setPower(double power)

    {

        this.power = power;

    }

    void shoot()

    {

        Thread t = new Thread(new Runnable()

        {

            @Override

            public void run()

            {

                executeShot();

            }

        });

        t.setDaemon(true);

        t.start();

    }

    private void executeShot()

    {

        if (projectile != null)

        {

            return;

        }

        projectile = new Projectile();

        Point2D velocity = 

            AffineTransform.getRotateInstance(angleRad).

                transform(new Point2D.Double(1,0), null);

        velocity.setLocation(

            velocity.getX() * power * 0.5, 

            velocity.getY() * power * 0.5);

        projectile.setVelocity(velocity);

        //System.out.println("Initial "+velocity);

        long prevTime = System.nanoTime();

        while (projectile.getPosition().getY() >= 0)

        {

            long currentTime = System.nanoTime();

            double dt = 3 * (currentTime - prevTime) / 1e8;

            projectile.performTimeStep(dt);

            prevTime = currentTime;

            paintingComponent.repaint();

            try

            {

                Thread.sleep(10);

            }

            catch (InterruptedException e)

            {

                Thread.currentThread().interrupt();

                return;

            }

        }

        projectile = null;

        paintingComponent.repaint();

    }

    Projectile getProjectile()

    {

        return projectile;

    }

}

class Projectile

{

    private final Point2D ACCELERATION = new Point2D.Double(0, -9.81 * 0.1);

    private final Point2D position = new Point2D.Double();

    private final Point2D velocity = new Point2D.Double();

    public Point2D getPosition()

    {

        return new Point2D.Double(position.getX(), position.getY());

    }

    public void setPosition(Point2D point)

    {

        position.setLocation(point);

    }

    public void setVelocity(Point2D point)

    {

        velocity.setLocation(point);

    }

    void performTimeStep(double dt)

    {

        scaleAddAssign(velocity, dt, ACCELERATION);

        scaleAddAssign(position, dt, velocity);

        //System.out.println("Now at "+position+" with "+velocity);

    }

    private static void scaleAddAssign(

        Point2D result, double factor, Point2D addend)

    {

        double x = result.getX() + factor * addend.getX();

        double y = result.getY() + factor * addend.getY();

        result.setLocation(x, y);

    }

}

class ProjectileShooterPanel extends JPanel

{

    private final ProjectileShooter projectileShooter;

    public ProjectileShooterPanel(ProjectileShooter projectileShooter)

    {

        this.projectileShooter = projectileShooter;

    }

    @Override

    protected void paintComponent(Graphics gr)

    {

        super.paintComponent(gr);

        Graphics2D g = (Graphics2D)gr;

        Projectile projectile = projectileShooter.getProjectile();

        if (projectile != null)

        {

            g.setColor(Color.RED);

            Point2D position = projectile.getPosition();

            int x = (int)position.getX();

            int y = getHeight() - (int)position.getY();

            g.fillOval(x-01, y-10, 20, 20);

        }

    }

}