Tile Map & collisions

Game Mechanics
#1

ok now, I’m developing a 2D platformer (e.g. super mario) like castlevania actually
ANYWAY

I’m having problems with performance for the following reason:

A map in my game has like 5 layers, for different purposes, and visual effects.

One layer is like everything the player cannot go through, I call it structures.

So in order to ensure you cannot walk through structures, I naturally check if a tile collides with the player.
I do this by using Rectangle.intersects(Rect…)

ok now for the problem


public boolean collide(Rectangle in) 
	{
		for (int y=0; y<height; y++)
	  	{
	  		for (int x=0; x<width; x++)
	  		{				  				
				if (tiles[x][y] != null)
	  			{
	  				if (in.intersects(new Rectangle((x*TILE_SIZE),(y*TILE_SIZE),(int)tiles[x][y].getPic().getWidth(),(int)tiles[x][y].getPic().getHeight())))
	  				{
	  					return true;
	  				}
	  			}
	  		}
	  	}
	  return false;
	}

Now this works fine, but the problem is: when the map gets bigger and bigger


for (int y=0; y<height; y++)
	  	{
	  		for (int x=0; x<width; x++)
	  		{				  				
				if (tiles[x][y] != null)
	  			{

this is done more often and often, and it slows the game down extremely, because I do this several times a frame for every object (player or enemies), naturally

I mean… I cannot check weather or not a tile collides with my player without doing a loop like this with every tile ?!

#2

http://kaioa.com/k/cellbbox.png

white rect=player bounding box
black dots=corners of that bbox
red=the tiles you have to check

Edit:
You know where the player’s sprite is, you know the size of it… hence you know the location of those 4 corners, you know the size of the cells… hence you know where each of those two loops has to start and stop (red tiles).

#3

ok works excellent =)

btw: my project needs already more heap size than the default (64M ?)
is it dangerous if the system needs too many heap ?

I mean I cannot even understand why, because all the content that is loaded is maybe 15 mb at max atm =0

#4

Images take widthheight3 bytes or widthheight4 bytes (if there is transparency involved) of RAM. But even opaque images may take the full widthheight4 bytes of RAM in order to be aligned. A 512x512 image will typically take 1mb of RAM.

Audio takes about 10mb per minute (if you don’t stream it).

2244,100*60=10,584,000 (in 60 seconds there are 41000 samples taking 16 bit [2 byte] each for both of those 2 channels)

#5

In your collide() method, you’re creating a lot of unnecessary Rectangle objects. You should be able to have one Rectangle object for the class, and in the loop, just set the dimensions before calling intersects(). I’m pretty sure Rectangle has methods like setWidth(), setHeight(), setX() etc.

#6

ok then it makes sense, since I’ve got a lot of transparent png’s

ya and thanks for the rectangle tip, I never know if it’s really that bad to create new variables in loops and stuff.
kinda need a easy way to measure how long some lines take…
of course i can get nanotime and stuff, but its a hassle =P

#7

Use a profiler. Netbeans got a very nice one for example.

#8

ya maybe later
I’m not using a mainstream java editor right now