Find the Intersection points of 2 rectangles

Question

we have two examples of rectangle:

 public static Rectangle rect1 = new Rectangle(20, 300, 400, 160);
 public static Rectangle rect2 = new Rectangle(150, 60, 230, 450);

The problem is to find an algorithm that finds all intersection points of these two rectangles

Sounds like a collision detection problem, http://stackoverflow.com/questions/335600/collision-detection-between-two-images-in-java — Danielson, Jun 26 '15 at 08:30
This sounds more like maths than Java. If you understand the maths of it, the coding should be simple. (I'd say the intersection is a region rather than a specific set of discrete points though.) — Jon Skeet, Jun 26 '15 at 08:30
there may be infinitely many solution as well as no solution for _Intersection points of 2 rectangles_ — mazhar islam, Jun 26 '15 at 08:37

score 2 · Answer 1 · answered Jun 26 '15 at 08:39

You can get the intersection points using inbuilt methods intersection

    Rectangle rect1 = new Rectangle(20, 300, 400, 160);
    Rectangle rect2 = new Rectangle(150, 60, 230, 450);

    Rectangle intersection = rect1.intersection(rect2);
    System.out.println(intersection);

Bepo · Answer 2 · 2015-06-26T10:16:55.540

You should do this:

public Area getRectanglesColisionArea(Rectangle rect1, Rectangle rect2){
    Area shape1 = new Area(rect1);
    Area shape2 = new Area(rect2);

    return shape1.intersect(shape2);
}

Returning area shape is the

To call the function just:

    Rectangle rect1 = new Rectangle(20, 300, 400, 160);
    Rectangle rect2 = new Rectangle(150, 60, 230, 450);
    Area result = getRectanglesColisionArea(rect1,rect2);

The Area result is the shape of the intersection, from there you can get the intersection points:

    Rectangle inters = result.getBounds();
    Double x1=inters.getX();
    Double y1=inters.getY();
    Double x2=inters.getX()+inters.getWidth();
    Double y2=inters.getY()+inters.getHeight();

score 0 · Answer 3 · answered Jun 26 '15 at 09:28

For 2 rectangles, there would be four cases for intersection,

One is inside another or they are totally disjoint - No point of intersection.
They share a single point - 1 point of intersection.
They intersect at exactly four points.
They share part of one or more sides - infinite points of intersection.

These conditions can be used to write tests to find the solution.

Find the Intersection points of 2 rectangles

3 Answers3