A more efficient way to pick and place tiles? - actionscript-3

Question

is it wrong to pick and place my tiles like this?
In other words, whats a better way to place the tiles so removing and adding a different tile is easy. Or what is a good method of doing so with the way i have it set up.
Whats a good way to reference a specific tile on the map?
public class Stage extends MovieClip
{
protected var tilesInWorld:Vector.<MovieClip> = new Vector.<MovieClip>();
public var worldTiles:Sprite;
protected var tile:MovieClip;
protected var TILE_SIZE:int = 5;
protected var map_width:int = 800;
protected var map_height:int = 600;
protected var pmap:BitmapData = new BitmapData(map_width,map_height);
protected var _seed:uint = Math.round(Math.random() * 100);
protected var grid_width:uint = new uint(map_width / TILE_SIZE);
protected var grid_height:uint = new uint(map_height / TILE_SIZE);
protected var heightmap:Array = new Array();
protected var pixelPoint:Point = new Point();
protected var darkest_pixel:Number = 1;
protected var brightest_pixel:Number = 0;
protected var hm :Number;
public function Stage()
{
pmap.perlinNoise(map_width,map_height, 6, _seed, true, false, 1, true);
for (var i:uint=0; i < grid_width; i++)
{
heightmap[i] = new Array();
for (var j:uint=0; j < grid_height; j++)
{
heightmap[i][j] = new uint();
}
}
//Divide the map in to a 7x7 grid and take data at each interval
for (i=0; i < grid_width; i++)
{
for (j=0; j < grid_height; j++)
{
pixelPoint.x = Math.round((i/grid_width) * pmap.width)+1;
pixelPoint.y = Math.round((j/grid_width) * pmap.height)+1;
heightmap[i][j] = pmap.getPixel(pixelPoint.x,pixelPoint.y);
heightmap[i][j] /= 0xffffff;
if (heightmap[i][j] < darkest_pixel)
{
darkest_pixel = heightmap[i][j];
}
}
}
//Adjust values to a min of 0
for (i=0; i < grid_width; i++)
{
for (j=0; j < grid_height; j++)
{
heightmap[i][j] -= darkest_pixel;
if (heightmap[i][j] > brightest_pixel)
{
brightest_pixel = heightmap[i][j];
}
}
}
//Adjust values to highest value of 1
for (i=0; i < grid_width; i++)
{
for (j=0; j < grid_height; j++)
{
heightmap[i][j] /= brightest_pixel;
}
}
worldTiles = new Sprite();
addChild(worldTiles);
placeTile();
}
The part below this is the main part im referring too
protected function placeTile()
{
for (var i=0; i < grid_width; i++)
{
for (var j=0; j < grid_height; j++)
{
hm = heightmap[i][j];
if (hm >= 0.84)
{
tile = new Water();
}
else if (hm >= 0.8 && hm < 0.84)
{
tile = new Shallow();
}
else if (hm >= 0.7 && hm < 0.8)
{
tile = new Sand();
}
else if (hm >= 0.2 && hm < 0.7)
{
tile = new Tile();
}
else
{
tile = new Stone();
}
tile.width = TILE_SIZE;
tile.height = TILE_SIZE;
worldTiles.x = 0;
worldTiles.y = 0;
tile.x = TILE_SIZE * (i % grid_width);
tile.y = TILE_SIZE * (j % grid_height);
tilesInWorld.push(tile);
worldTiles.addChild(tile);
}
}
}
}
is there a more efficient way of picking and placing the tiles?
and while i have your attention, how can i go about deleting and replacing the tiles?

Answer 1

It would be better to not do so many array look-ups.
//..
var hm :Number;
for (var i=0; i < grid_width; i++)
{
for (var j=0; j < grid_height; j++)
{
hm = heightmap[i][j];
if (hm >= 0.84)
{
tile = new Water();
}
else if ( hm >= 0.8 && hm < 0.84)
{
//...
Also you might want to look at object pooling. Here is a nice video tutorial about object pooling.
Apart of that I can't see much more to optimise here. But I am sure others will give you more tips.