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  Basic 2D Tile Collision  (Read 2414 times)
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Offline relminator
« Posted 2013-05-21 07:48:09 »

Hello,

I've noticed that there are a lot of 2d platforming related questions lately so I hacked up a simple demo.

Collisions are axis-based so this would work wether your player size is bigger or smaller than the map tiles.

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package net.phatcode.rel;

/**
 * @author Richard Eric M. Lope (relminator)
 *
 */



public class Collision
{

   public enum CollisionType
   {
      COLLIDE_NONE,
      COLLIDE_FLOOR,
      COLLIDE_WALL,
      COLLIDE_CEILING,
     
   }
   
   private static int tileX;
   private static int tileY;
   
   public static boolean collideWalls( float offset, Entity e, LevelMap levelMap )
   {
     
      int ix = (int)(e.getX() + offset);
      int iy = (int)e.getY();
     
      int hei = (int)e.getHeight();
     
      int tileYpixels = iy - ( iy % Constants.TILE_SIZE );
      int testEnd = iy + hei;  
     
      tileX = ix / Constants.TILE_SIZE;
      tileY = tileYpixels / Constants.TILE_SIZE;
     
     
      int[][] map = levelMap.getMap();
      while( tileYpixels <= testEnd )
      {      
         if( map[tileX][tileY] > 0 )
         {
            return true;
         }
         tileY++;
         tileYpixels += Constants.TILE_SIZE;
      }
     
      return false;
   }
   
   public static boolean collideFloors( float offset, Entity e, LevelMap levelMap )
   {
     
      int ix = (int)e.getX();
      int iy = (int)(e.getY() + offset);
     
      int wid = (int)e.getWidth();
     
      int tileXpixels = ix - ( ix % Constants.TILE_SIZE );
      int testEnd = ix + wid;  
     
      tileX = tileXpixels / Constants.TILE_SIZE;
      tileY = iy / Constants.TILE_SIZE;
     
     
      int[][] map = levelMap.getMap();
      while( tileXpixels <= testEnd )
      {      
         if( map[tileX][tileY] > 0 )
         {
            return true;
         }
         tileX++;
         tileXpixels += Constants.TILE_SIZE;
      }
     
      return false;
   }
   
   public static CollisionType collideOnMap(  Entity e, LevelMap levelMap )
   {
     
      tileX = 0;
      tileY = 0;
      CollisionType collision = CollisionType.COLLIDE_NONE;
     
      if( e.getDx() > 0 )
      {
     
         if( collideWalls( e.getDx() + e.getWidth(), e, levelMap ) )
         {
            e.setX( (tileX  * Constants.TILE_SIZE) - e.getWidth() - 1 );
            collision = CollisionType.COLLIDE_WALL;
         }
         else
         {
            e.addX( e.getDx() );
         }
   
      }
     
      else if( e.getDx() < 0 )
      {

         if( collideWalls( e.getDx(), e, levelMap ) )
         {
            e.setX( ( tileX + 1 ) * Constants.TILE_SIZE + 1 );
            collision = CollisionType.COLLIDE_WALL;
         }
         else
         {
            e.addX( e.getDx() );
         }
         
      }
     
     
      if( e.getDy() < 0 )
      {
         
         if( collideFloors( e.getDy(), e, levelMap ) )
         {
            e.setY( ( tileY + 1 ) * Constants.TILE_SIZE + 1 );
            e.setDy( 0 );
            collision = CollisionType.COLLIDE_CEILING;
         }
         else
         {
            e.addY( e.getDy() );
            e.addDy( Constants.GRAVITY );
         }
         
      }
      else
      {
         
         if( collideFloors( e.getDy() + e.getHeight(), e, levelMap ) )
         {
            e.setY( (tileY  * Constants.TILE_SIZE) - e.getHeight() - 1 );
            e.setDy( 1 );
            collision = CollisionType.COLLIDE_FLOOR;
         }
         else
         {
            e.addY( e.getDy() );
            e.addDy( Constants.GRAVITY );
         }
      }
     
     
      return collision;
     
   }
   
   
}


Full source and binary here:

http://rel.phatcode.net/junk.php?id=143

Screen:



I'm not sure if the links work as I'm using a phone to post.

Enjoy!
Offline Sir_Wabbit

Senior Newbie


Medals: 1



« Reply #1 - Posted 2013-05-21 11:43:14 »

very helpful! simple and clean.
you could always add a comment line with a little description of the different methods, but the names of the methods are pretty descriptive anyway. great work Smiley
Offline Dobby90

Junior Newbie





« Reply #2 - Posted 2013-05-22 01:16:44 »

been trying to find something like this for the last few days Smiley

thank you for sharing this code i can now get one step further to building my first game
Games published by our own members! Check 'em out!
Legends of Yore - The Casual Retro Roguelike
Offline relminator
« Reply #3 - Posted 2013-05-22 02:15:34 »

very helpful! simple and clean.
you could always add a comment line with a little description of the different methods, but the names of the methods are pretty descriptive anyway. great work Smiley


Sorry about that.  My laptop was getting low on battery so I sped up the process a bit.
Offline __iCode__

Senior Newbie





« Reply #4 - Posted 2013-08-09 11:42:40 »

Thanks heaps for this! Taking the confusion out of tutorials Wink
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