Even though user2221343 already answered Monkeybro10's question, I thought it might be helpful in some cases to know, that the outline of a shape might play a role if you use his described technique:
For example, if you draw two polygons, the collision of them won't be detected if it occurs only on the exact outline of the polygons. Only, if the areas that are included inside the polygons' outlines will overlap, the collision is detected.
If you fill two polygons, but don't draw them, the collision will be detected even on the outline of the visible area.
I wrote a small example to show what I mean. Either uncomment the draw or fill command, and rise the second polygon vertically by one pixel by uncommenting the given line. Run the code and watch the result in the JFrame. If the second Polygon is risen, and both polygons are only visible by the "fill" command, they intersect with their outlines and collision is detected. If the second polygon is not risen, and both polygons are visible by the "draw" command, they intersect with their outlines but collision is not detected:
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Polygon;
import java.awt.geom.Area;
import javax.swing.JFrame;
public class Test {
private JFrame frame;
private Polygon polygon1;
private Polygon polygon2;
/**
* Launch the application.
*/
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
try {
Test window = new Test();
window.frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public Test() {
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize() {
frame = new JFrame(){
private static final long serialVersionUID = 1L;
@Override
public void paint(Graphics g){
super.paint(g);
doDrawing(g);
}
};
frame.setBounds(100, 100, 450, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
int nShape1 = 4;
int xPoly1[] = {30,50,50,30};
int yPoly1[] = {30,30,50,50};
polygon1 = new Polygon(xPoly1,yPoly1,nShape1);
int nShape2 = 4;
int xPoly2[] = {35,55,55,35};
int yPoly2[] = {50,50,70,70};
// uncomment next line to rise second polygon vertically by one pixel
//yPoly2[] = {49,49,69,69};
polygon2 = new Polygon(xPoly2,yPoly2,nShape2);
}
public synchronized void doDrawing(Graphics g){
g.setColor(new Color(255,0,0));
// if you draw the polygon, collision on the exact outline won't be detected.
// uncomment draw or fill command to see what I mean.
g.drawPolygon(polygon1);
g.fillPolygon(polygon1);
g.setColor(new Color(0,0,255));
// if you draw the polygon, collision on the exact outline won't be detected.
// uncomment draw or fill command to see what I mean.
g.drawPolygon(polygon2);
g.fillPolygon(polygon2);
Area area = new Area(polygon1);
area.intersect(new Area(polygon2));
if(!area.isEmpty()){
System.out.println("intersects: yes");
}
else{
System.out.println("intersects: no");
}
}
}
