Sorting Tables of Tables

[Kingdaro]

I am very frustrated trying to find a function that won't make my tiles in my isometric game look like this:

ARRRRRGH.png (4.33 KiB) Viewed 1963 times

The game draws the tile images via a table of tables, as the title states:

Code: Select all

sX = 0
sY = 0
tiles = {}

grass = love.graphics.newImage("grass.png")
forest = love.graphics.newImage("forest.png")

table.insert(tiles,{grass,0,0})

table.insert(tiles,{forest,0,1})
table.insert(tiles,{forest,0,-1})
table.insert(tiles,{forest,1,0})
table.insert(tiles,{forest,-1,0})

function love.draw()
	for i,v in pairs(tiles) do
		local img = v[1]
		local x = v[2]
		local y = v[3]
		
		love.graphics.draw(img,
		(sX+(x*28)+(y*28))+(400-32),
		(sY+(x*14)+(y*-14))+(300-32)
		)
	end
end

And I need a function that will sort the tables by the third value, greatest to least, and the tables that have equal third values will be sorted by their second values,least to greatest. Example:

{grass,0,3}
{grass,0,2}
{grass,3,1}
{grass,4,1}
{grass,5,1}
{grass,0,0}

I just can't seem to find the right math to do this, and it'd be cool if someone could help me.

[BlackBulletIV]

Code: Select all

table.sort(tiles, function(a, b)
  return b[3] < a[3]
end

The table.sort function is your friend. The function tells it how to deal with two items in the table. To quote from Programming in Lua:

This order function receives two arguments and must return true if the first argument should come first in the sorted array.

[Kingdaro]

The solution you gave alone wasn't satisfiable, but I screwed around with it and got the desired result. Thanks.

[BlackBulletIV]

What went wrong with it?

[Taehl]

I had this same problem a long, long time ago. Except, Isome has its tiles in three dimensions, making things even trickier.

[Jasoco]

Is there any reason you're not using a grid?

Code: Select all

tile = {}
for x=0,map_width-1 do
  tile[x] = {}
  for y=0,map_height-1 do
    tile[x][y] = tile_data
  end
end

Then you wouldn't need sorting as you'd just draw from 0,0 to map_width,map_height by looping through the same way.

Code: Select all

for x=0,map_width-1 do
  for y=0,map_height-1 do
    --draw tile here
  end
end

You'd only have to sort objects like characters that can move around the map by their Y value.

Of course drawing the tiles and translating the X and Y's to isometric coordinates would require some more math...