Example of collision detection using java.awt.geom.Area with AffineTransform's

DemoPainter.java

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package collisiondemo;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.AffineTransform;
import javax.swing.JComponent;

/**
 *
 * @author avh4
 */
public class DemoPainter extends JComponent {
    
    private DemoState theDemoState;
    
    @Override
    public void paint(Graphics g) {
        Graphics2D g2 = (Graphics2D)g;
        

        // Draw the triangle
        Triangle t = theDemoState.getTheTriangle();
        g2.setTransform(new AffineTransform());
        g2.setColor(Color.GREEN);
        if (theDemoState.doTrianglesIntersect())
        {
            g2.setColor(Color.BLUE);
        }
        g2.translate(t.getX(), t.getY());
        g2.rotate(Math.toRadians(-90));
        g2.rotate(Math.toRadians(t.getHeading()));
        g2.scale(50, 100);
        g2.fillPolygon(t.getShape());
        
        // Draw the main triangle's center dot
        g2.setTransform(new AffineTransform());
        g2.setColor(Color.RED);
        g2.translate(t.getX(), t.getY());
        g2.fillOval(-1, -1, 3, 3);
        
        // Draw the tiny triangle
        t = theDemoState.getTinyTriangle();
        g2.setTransform(new AffineTransform());
        g2.setColor(Color.GREEN);
        if (theDemoState.doTrianglesIntersect())
        {
            g2.setColor(Color.BLUE);
        }
        g2.translate(t.getX(), t.getY());
        g2.rotate(Math.toRadians(-90));
        g2.rotate(Math.toRadians(t.getHeading()));
        g2.scale(4, 7);
        g2.fillPolygon(t.getShape());
        
        // Draw the tiny triangle's center dot
        g2.setTransform(new AffineTransform());
        g2.setColor(Color.RED);
        g2.translate(t.getX(), t.getY());
        g2.fillOval(-1, -1, 3, 3);
    }
    
    public void setTheDemoState(DemoState theDemoState)
    {
        this.theDemoState = theDemoState;
    }

}

DemoState.java

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package collisiondemo;

import java.awt.geom.AffineTransform;
import java.awt.geom.Area;

/**
 *
 * @author avh4
 */
public class DemoState {
    
    private Triangle mainTriangle;
    private Triangle tinyTriangle;
    
    public void setUpDemo() {
        mainTriangle = new Triangle();
        getTheTriangle().setX(200);
        getTheTriangle().setY(250);
        getTheTriangle().setHeading(0);
        
        tinyTriangle = new Triangle();
        tinyTriangle.setX(300);
        tinyTriangle.setY(300);
        tinyTriangle.setHeading(80);
    }
    
    public void moveObjects() {
        getTheTriangle().setX(getTheTriangle().getX() + 1);
        
        mainTriangle.setHeading(mainTriangle.getHeading() + 1);
        tinyTriangle.setHeading(tinyTriangle.getHeading() - 2);
    }
    
    public boolean doTrianglesIntersect() {
        
        // Set up the tiny triangle transform
        AffineTransform tinyTriangleTransform = new AffineTransform();
        tinyTriangleTransform.translate(tinyTriangle.getX(), tinyTriangle.getY());
        tinyTriangleTransform.rotate(Math.toRadians(-90));
        tinyTriangleTransform.rotate(Math.toRadians(tinyTriangle.getHeading()));
        tinyTriangleTransform.scale(4, 7);
        
        // Create the transformed tiny triangle area from it's shape
        Area tinyArea = new Area(tinyTriangle.getShape());
        tinyArea.transform(tinyTriangleTransform);

        // Set up the main triangle transform
        AffineTransform mainTriangeTransform = new AffineTransform();
        mainTriangeTransform.translate(mainTriangle.getX(), mainTriangle.getY());
        mainTriangeTransform.rotate(Math.toRadians(-90));
        mainTriangeTransform.rotate(Math.toRadians(mainTriangle.getHeading()));
        mainTriangeTransform.scale(50, 100);

        // Create the transformed main triangle area from it's shape
        Area mainTriangleArea = new Area(mainTriangle.getShape());
        mainTriangleArea.transform(mainTriangeTransform);
        
        // Find the overlap of the main triangle area and the tiny triangle area
        Area overlapArea = (Area) mainTriangleArea.clone();
        overlapArea.intersect(tinyArea);
        
        return ! overlapArea.isEmpty();
    }

    public Triangle getTinyTriangle()
    {
        return tinyTriangle;
    }

    public Triangle getTheTriangle()
    {
        return mainTriangle;
    }

}

DemoWindow.java

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package collisiondemo;

import java.awt.Component;
import javax.swing.JFrame;

/**
 *
 * @author avh4
 */
public class DemoWindow {
    
    private DemoPainter thePainter;
    
    public void createWindow() {
        
        JFrame window = new JFrame("Collision Demo");
        window.add(thePainter);
        window.pack();
        window.setSize(700, 700);
        window.setLocationRelativeTo(null);
        window.setVisible(true);
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        
    }

    public void setThePainter(DemoPainter thePainter)
    {
        this.thePainter = thePainter;
    }

}

Main.java

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package collisiondemo;

import java.util.logging.Level;
import java.util.logging.Logger;

/**
 *
 * @author avh4
 */
public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        
        DemoState theDemoState = new DemoState();
        theDemoState.setUpDemo();
        
        DemoPainter mainPainter = new DemoPainter();
        mainPainter.setTheDemoState(theDemoState);
        
        DemoWindow mainWindow = new DemoWindow();
        mainWindow.setThePainter(mainPainter);
        mainWindow.createWindow();
        
        while (true) {
            
            mainPainter.repaint();
            try
            {

                Thread.sleep(100);
            }
            catch (InterruptedException ex)
            {
                Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
            }
            
            theDemoState.moveObjects();
        }
    }

}

Triangle.java

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package collisiondemo;

import java.awt.Polygon;

/**
 *
 * @author avh4
 */
public class Triangle {
    private double x;
    private double y;
    private double heading;
    
    int xpoints[] = { 0, 1, -1, 0 };
    int ypoints[] = { 1, 0,  0, 1 };
    private Polygon shape = new Polygon(xpoints, ypoints, xpoints.length);

    public double getX()
    {
        return x;
    }

    public void setX(double x)
    {
        this.x = x;
    }

    public double getY()
    {
        return y;
    }

    public void setY(double y)
    {
        this.y = y;
    }

    public double getHeading()
    {
        return heading;
    }

    public void setHeading(double heading)
    {
        this.heading = heading;
    }

    public Polygon getShape()
    {
        return shape;
    }

}