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  Collision Detection For My Game  (Read 981 times)
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Offline ToXSiK

Senior Newbie





« Posted 2011-05-20 20:02:24 »

Hey guys, so I have a game I am developing which is a 2d sidescroller.  I have an arraylist of all elements in the world and they have a location object attatched to each of them.

Each tile is 24 x 24 pixels, the character is 24 x 48 characters.

I have developed an object called "Location" which keeps track of all objects x and y's.

For instance, I can say player.getLocation().getX() to get where it is on the X axis, same for Y.

I want the player to be able to move left, right, and jump.  I have the jumping physics worked out, but collision detection is just being a pain. 

Currently, in my Location class I have a class called overlaps(Location otherLoc), so I can say like

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if(player.overlaps(elements.get(i).getLocation())


And loop through, brute force checking every single object on the screen and seeing if it overlaps.

My overlaps method is as follows, I beleive it is written wrong but I have written it about 4 times to I am a little fed up with it, maybe you can figure it out.

Note:  Datastore.TILE_SIZE = 24.

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   public boolean overlaps(Location _toCompare)
   {
      if((((this.getX() >= _toCompare.getX()) &&
         (this.getX() <= (_toCompare.getX() + Datastore.TILE_SIZE)) &&
         (this.getY() <= (_toCompare.getY())) &&  
         (this.getY() >= (_toCompare.getY() + Datastore.TILE_SIZE)))) ||
         
        (((this.getX() + Datastore.TILE_SIZE) >= (_toCompare.getX()) &&      
         (this.getX() + Datastore.TILE_SIZE) <= (_toCompare.getX() + Datastore.TILE_SIZE) &&
         this.getY() <= (_toCompare.getY()) &&  
         this.getY() >= (_toCompare.getY() + Datastore.TILE_SIZE))) ||
         
         ((this.getX() >= _toCompare.getX() &&      
         this.getX() <= (_toCompare.getX() + Datastore.TILE_SIZE) &&
         (this.getY() + Datastore.TILE_SIZE) >= (_toCompare.getY()) &&  
         (this.getY() + Datastore.TILE_SIZE) <= (_toCompare.getY() + Datastore.TILE_SIZE))) ||        
         
        (((this.getX() + Datastore.TILE_SIZE) >= _toCompare.getX() &&      
         (this.getX() + Datastore.TILE_SIZE) <= (_toCompare.getX() + Datastore.TILE_SIZE) &&
         (this.getY() + Datastore.TILE_SIZE) >= (_toCompare.getY()) &&  
         (this.getY() + Datastore.TILE_SIZE) <= (_toCompare.getY() + Datastore.TILE_SIZE))))
      {
         return true;
      } else {
         return false;
      }
   }
/code]
Offline zoto

Senior Member


Medals: 4



« Reply #1 - Posted 2011-05-20 21:29:32 »

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   public boolean overlaps(Location toCompare)
   {
      if( contains(toCompare) ) // Top left corner
        return true;
      if( contains(toCompare.getMaxX(), toCompare.getY()) ) // Top right corner
        return true;
      if( contains(toCompare.getX(), toCompare.getMaxY()) ) // Bottom left corner
        return true;
      if( contains(toCompare.getMaxX(), toCompare.getMaxY()) ) // Bottom right corner
        return true;
      return false;
   }

   public boolean contains(Location toCompare){
      return contains(toCompare.getX(), toCompare.getY());
   }
   
   public boolean contains(int x, int y){
      return (x >= getX() && x <= getMaxX() &&
            y >= getY() && y <= getMaxY());
   }


The getMaxX is just x + Datastore.TILE_SIZE, same for the y except for the player its y + Datastore.TILE_SIZE * 2.

This code will not work properly if you use blocks that are bigger than the player but I'm guessing that's not a possibility.
Offline ra4king

JGO Kernel


Medals: 336
Projects: 2
Exp: 5 years


I'm the King!


« Reply #2 - Posted 2011-05-20 22:18:34 »

Also, I think "intersects" is a better method name than "overlap" Wink

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