Collision detection help in Java applet

Question

I'm making a flappy bird game, and I'm trying to make a statement where the bird will die if it touches one of the two pipes.

Here's my collision code which runs in the 'run' method.

    int appletsize_x = 800;
    int appletsize_y = 500;

    int x_pos = appletsize_x / 2;
    int y_pos = appletsize_y / 2;

    int x_pos2 = 100;
    int y_pos2 = -50;

    int x_pos6 = 100;
    int y_pos6 = 350;

      public void run ()
    {

            if (x_pos >= x_pos2
                    || (x_pos <= x_pos6))
            {
                collision = true;
                if (collision = true)
                {
                    startgame = false;
                }
            }
}

Of course there's more to it, I was just wondering how I'd make a collision detection for the bird and pipe.

The main problem is that my collision boolean and start game boolean aren't doing anything. I'm trying to make it so that if the bird image touches the pipe image, it sets to a game over. — Sumsore Musakheel, Jan 13 '15 at 05:06

score 2 · Answer 1 · edited May 23 '17 at 12:05

If those pipes are line shaped and if you know their line formula(or at least coords. of end points), then you can use "perpendicular distance to a line" calculation to know if it is close enough.

That is already answered: here

If a pipe needs to be a complex shape, and if you are ok with a particle simulation, here is very simple, inefficient but easy to use example that builds an object on a group of collidable objects and checks collision with a single object(bird):

import java.util.ArrayList;
import java.util.List;


public class FactoryClass {

    public class CollidableResult
    {
        public Collidable c;
        public boolean yesItIs;
    }

    public class Collidable
    {
        public float x;
        public float y;
        public static final float tolerance=600.001f; 
        public Collidable()
        {
            //just giving random starting coordinates for fun
            // so the object may not be a pipe with these. Please add some parameters
            // for your needs
            x=(float) (Math.random()*1000.0);
            y=(float) (Math.random()*1000.0);         
        }
        public CollidableResult isTooClose(Collidable c)
        {
            float deltax=(c.x - this.x);
            float deltay=(c.y - this.y);
            // checks if close enough
            if(Math.sqrt(deltax*deltax + deltay*deltay)<tolerance) 
            {
                CollidableResult cr=new CollidableResult();
                cr.yesItIs=true;
                cr.c=this;
                return cr;              
            }
            else
            {
                CollidableResult cr=new CollidableResult();
                cr.yesItIs=false;
                cr.c=null;
                return cr;   
            }
        }

        public List<Collidable> collide(List<Collidable> cl)
        {
            List<Collidable> c=new ArrayList<Collidable>();
            for(Collidable co:cl)
            {
                if(this.isTooClose(co).yesItIs)
                {
                    c.add(co);
                }
            }
            return c;       
        }
        public void die()
        {
            // AnimateDead();
            try {this.finalize();} catch (Throwable e) {e.printStackTrace();}
            System.gc();        
        }
        public void levelUp()
        { 
            System.out.println("Level Up! Hit points incremented by 12.");  
        }

    }

    public static void main(String[] args) {
        FactoryClass factory=new FactoryClass();
        List<Collidable> pointsOfAPipe = new ArrayList<Collidable>();
        pointsOfAPipe.add(factory.new Collidable(/*parameters for pipe */));
        pointsOfAPipe.add(factory.new Collidable(/*parameters for pipe */));
        pointsOfAPipe.add(factory.new Collidable(/*parameters for pipe */));
        //...
        // build your pipe object using many colllidable points (can build complex shapes with this)
        //...
        pointsOfAPipe.add(factory.new Collidable(/*parameters for pipe */));
        pointsOfAPipe.add(factory.new Collidable(/*parameters for pipe */));
        pointsOfAPipe.add(factory.new Collidable(/*parameters for pipe */));

        Collidable bird=factory.new Collidable();
        bird.x=100;
        bird.y=350;
        List<Collidable> collisionPoints = bird.collide(pointsOfAPipe);
        if(collisionPoints.size()>0)
        {
            System.out.println("Bird collides pipe on "+collisionPoints.size()+" different points and dies");
            bird.die();
        }
        else {System.out.println("Bird survived");bird.levelUp();}  
    }   
}

most of the time, output for me is:

Bird collides pipe on 4 different points and dies

You can add another class that integrates different collections to make even more complex scenarios such as rotating turrets mounted on a spaceship which fires beams to cut pipes and even collides other spaceships and birds.

Collision detection help in Java applet

1 Answers1