colllision rectangle-polygon

[marina]

Hello!!
Well,I have some problems with my program( I am new to java..).I want to know if there is a collision between a polygon and a rectangle.How am I going to do that??

for the rectangle I used the method getBounds():

public Rectangle r;
Graphics g;
	
	public Obstacle(int x,int y,int w,int h)
	{
		r=new Rectangle(x,y,w,h);
	}
	
	
	 public Rectangle getBounds() {
	       return new Rectangle(r.x,r.y,r.width,r.height);
	       }
	
	public void draw(Graphics gr)
  	{
  		g=gr;
  		g.setColor(Color.red);
  		g.fillRect(r.x,r.y,r.width,r.height);
  	}

Am i able to do the same for the polygon (use getbounds) and then use the intersects method?

int[] xs = { (int)((Diameter/2)*1.4), -(int)((Diameter/2)*0.6), -(int)((Diameter/2)*0.6) };
int[] ys = { 0, (int)((Diameter/2)*0.6), -(int)((Diameter/2)*0.6) };
int[] xpoints = {0,0,0};
int[] ypoints = {0,0,0};

 double sin = Math.sin(direction);
 double cos = Math.cos(direction);

 for(int tripoint = 0;tripoint < 3;tripoint++){
    xpoints[tripoint] = (int)x + (int)(cos * xs[tripoint] + -sin * ys[tripoint]);
    ypoints[tripoint] = (int)y + (int)(sin * xs[tripoint] + cos * ys[tripoint]);
	                 }
	         
	                g.setColor(color);
	                g.fillPolygon(xpoints,ypoints,3);
	                g.drawPolygon(xpoints,ypoints,3);

getBounds for the polygon:

public Rectangle getBounds() {
    	   return new Rectangle(x+(int)((Diameter)*1.4),y+(int)((Diameter)*0.6),(int)((Diameter)*1.4),(int)((Diameter)*0.6));
       }

Thanks in advance!

[hardwired]

The Polygon class api shows a method

boolean intersects(Rectangle2D r)

that might be helpful.

[marina]

thanks for the reply!
My problem is how to get the bounds of the polygon..
I know about intersects method and i used it in my code but sometimes it doesn't "see" that there is a collision between the rectangle and the polygon.So I assumed there's something wrong with the polygon's getbounds method..

[hardwired]

Using the bounds of a polygon to test for intersection is using the Rectangle intersects method. Bounds => Rectangle. Using the Polygon intersects method is a different thing. To demonstrate the difference:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class PolygonIntersection extends JPanel {
    Polygon polygon;
    Rectangle rect;
    boolean selected = false;
    boolean useBounds = false;

    public PolygonIntersection() {
        int[][] pts = {
            { 125, 176, 73 }, { 40, 130, 130 }
        };
        polygon = new Polygon(pts[0], pts[1], 3);
        rect = new Rectangle(100, 150, 175, 75);
        addMouseListener(ma);
        addMouseMotionListener(ma);
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                            RenderingHints.VALUE_ANTIALIAS_ON);
        Color color = selected ? Color.red : Color.blue;
        g2.setPaint(color);
        g2.draw(polygon);
        g2.draw(rect);
        g2.setPaint(Color.pink);
        g2.draw(polygon.getBounds());
    }

    private void checkForIntersection() {
        selected = useBounds ? polygon.getBounds().intersects(rect)
                             : polygon.intersects(rect);
        repaint();
    }

    private JPanel getLastPanel() {
        String[] ids = { "bounds", "polygon" };
        ActionListener al = new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String id = e.getActionCommand();
                boolean selected = ((JRadioButton)e.getSource()).isSelected();
                useBounds = id.equals("bounds") && selected;
                checkForIntersection();
            }
        };
        ButtonGroup group = new ButtonGroup();
        JPanel panel = new JPanel();
        for(int i = 0; i < ids.length; i++) {
            boolean b = useBounds ? i == 0 : i > 0;
            JRadioButton rb = new JRadioButton(ids[i], b);
            rb.setActionCommand(ids[i]);
            rb.addActionListener(al);
            group.add(rb);
            panel.add(rb);
        }
        return panel;
    }

    public static void main(String[] args) {
        PolygonIntersection test = new PolygonIntersection();
        JFrame f = new JFrame("drag the polygon");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(test);
        f.add(test.getLastPanel(), "Last");
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }

    private MouseAdapter ma = new MouseAdapter() {
        boolean dragging = false;
        Point start;

        public void mousePressed(MouseEvent e) {
            Point p = e.getPoint();
            if(polygon.contains(p)) {
                start = p;
                dragging = true;
            }
        }

        public void mouseReleased(MouseEvent e) {
            dragging = false;
        }

        public void mouseDragged(MouseEvent e) {
            if(dragging) {
                Point p = e.getPoint();
                int x = p.x - start.x;
                int y = p.y - start.y;
                polygon.translate(x, y);
                start.setLocation(p);
                checkForIntersection();
            }
        }
    };
}

[marina]

thanks very much for the reply!!I 'll study that code and hope to solve my problem..