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Niles
Niles wrote ...

2013/10/21

Bouncing - Ball stuck at the edge

Niles Niles

2013/10/21

#
Hey, I have a simple scenario where a ball simply bounces when it hits the wall. Turning 180 degrees does not bounce off according to the angle. In order for it to bounce off walls I used: 
setRotation(getRotation()*-1);
This works vertically but horizontally the ball gets stuck. Here is the code for the ball: 
import greenfoot.*;

public class ball extends Actor
{
    /**
     * Act - do whatever the ball wants to do. This method is called whenever
     * the 'Act' or 'Run' button gets pressed in the environment.
     */
    public void act() 
    {
        move(5);
        checkWalls();
    }    

    public void checkWalls(){
        if(atWorldEdge()){
            setRotation(getRotation()*-1);
        }
    }

    public boolean atWorldEdge()  
    {  
        if(getX() < 10 || getX() > getWorld().getWidth() - 10)  
            return true;  
        if(getY() < 10 || getY() > getWorld().getHeight() - 10)  
            return true;  
        else  
            return false;  
    }  
}
Zamoht Zamoht

2013/10/21

#
Changed the code a little and made sure that the ball does not get stuck in the wall. 
public class ball extends Actor  
{  
    private int oldEdge;
    /** 
     * Act - do whatever the ball wants to do. This method is called whenever 
     * the 'Act' or 'Run' button gets pressed in the environment. 
     */  
    public void act()   
    {  
        move(5);  
        checkWalls();  
    }      
  
    public void checkWalls(){  
        int edge = atWorldEdge();
        if(edge >= 0 && edge != oldEdge){  
            setRotation(getRotation()*-1+(180*(edge%2)));  
        }  
        oldEdge = edge;
    }  
  
    public int atWorldEdge()    
    {    
        if(getX() < 10) return 1; 
        if(getX() > getWorld().getWidth() - 10) return 3;    
        if(getY() < 10) return 2;
        if (getY() > getWorld().getHeight() - 10) return 4; 
        return -1;
    }    
}
Niles Niles

2013/10/21

#
Thanks!
chamuzi3 chamuzi3

2014/10/4

#
same problem here i cant seem to make it bounce off that horizontal world edge.
danpost danpost

2014/10/4

#
Try using 'move(-5)' before changing the rotation (see line 17 of the code Zamoht supplied). You may be able to remove 'oldEdge' from the code after inserting this line. However, I think it could still be buggy if both edges are encountered simultaneously. Maybe simplifying might help. Try this: 
public class ball extends greenfoot.Actor  
{  
    public void act()   
    {  
        move(5);  
        checkWalls();  
    }      
  
    public void checkWalls()
    {  
        boolean atXEdge = getX() < 10 || getX() > getWorld().getWidth()-10;
        boolean atYEdge = getY() < 10 || getY() > getWorld().getHeight()-10;
        if (atXEdge || atYEdge) move(-5);
        if (atXEdge) setRotation(540-getRotation());
        if (atYEdge) setRotation(360-getRotation());
    }  
}
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