Tutorial:Fine Tile-based Scrolling

This is an expansion upon the code in Tile-based Scrolling. It assumes a tile size of 16x16 and a window size of 320x240.

function love.load()
	-- our tiles
	tile = {}
	for i=0,3 do -- change 3 to the number of tile images minus 1.
		tile[i] = love.graphics.newImage( "tile"..i..".png" )
	end
	
	-- the map (random junk + copy and paste)
	map={
	{ 3, 3, 3, 3, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0}, 
	{ 3, 1, 0, 0, 2, 2, 2, 0, 3, 0, 3, 0, 1, 1, 1, 0, 0, 3, 0, 0, 0},
	{ 3, 1, 0, 0, 2, 0, 2, 0, 3, 0, 3, 0, 1, 0, 0, 0, 0, 0, 3, 0, 0},
	{ 3, 1, 1, 0, 2, 2, 2, 0, 0, 3, 0, 0, 1, 1, 0, 0, 0, 0, 0, 3, 0},
	{ 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 3},
	{ 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 2},
	{ 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 2, 2, 2, 0, 3, 3, 3, 0, 1, 1, 1, 0, 2, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 2, 0, 0, 0, 3, 0, 3, 0, 1, 0, 1, 0, 2, 0, 0, 0, 0, 0, 0, 1},
	{ 0, 2, 0, 0, 0, 3, 0, 3, 0, 1, 0, 1, 0, 2, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 2, 2, 2, 0, 3, 3, 3, 0, 1, 1, 1, 0, 2, 2, 2, 0, 0, 0, 0, 0},
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, 
	{ 0, 1, 0, 0, 2, 2, 2, 0, 3, 0, 3, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0},
	{ 0, 1, 0, 0, 2, 0, 2, 0, 3, 0, 3, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 1, 1, 0, 2, 2, 2, 0, 0, 3, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 3},
	{ 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0},
	{ 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
	{ 0, 1, 0, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
	}
		
	-- map variables
	map_w = #map[1] -- Obtains the width of the first row of the map
	map_h = #map -- Obtains the height of the map
	map_x = 0
	map_y = 0
	map_display_buffer = 2 -- We have to buffer one tile before and behind our viewpoint.
                               -- Otherwise, the tiles will just pop into view, and we don't want that.
	map_display_w = 20
	map_display_h = 15
	tile_w = 16
	tile_h = 16
end
	
function draw_map()
	offset_x = map_x % tile_w
	offset_y = map_y % tile_h
	firstTile_x = math.floor(map_x / tile_w)
	firstTile_y = math.floor(map_y / tile_h)
	
	for y=1, (map_display_h + map_display_buffer) do
		for x=1, (map_display_w + map_display_buffer) do
			-- Note that this condition block allows us to go beyond the edge of the map.
			if y+firstTile_y >= 1 and y+firstTile_y <= map_h
				and x+firstTile_x >= 1 and x+firstTile_x <= map_w
			then
				love.graphics.draw(
					tile[map[y+firstTile_y][x+firstTile_x]], 
					(x*tile_w) - offset_x - tile_w/2, 
					(y*tile_h) - offset_y - tile_h/2)
			end
		end
	end
end

function love.update( dt )
	-- get input
	if love.keyboard.isDown( "up" ) then
		map_y = map_y-2
	end
	if love.keyboard.isDown( "down" ) then
		map_y = map_y+2
	end

	if love.keyboard.isDown( "left" ) then
		map_x = map_x -2
	end
	if love.keyboard.isDown( "right" ) then
		map_x = map_x+2
	end
	if love.keyboard.isDown( "escape" ) then
		love.event.push( "q" )
	end

	-- check boundaries. remove this section if you don't wish to be constrained to the map.
	if map_x < 0 then
		map_x = 0
	end

	if map_y < 0 then
		map_y = 0
	end	
 
	if map_x > map_w * tile_w - map_display_w * tile_w then
		map_x = map_w * tile_w - map_display_w * tile_w
	end
 
	if map_y > map_h * tile_h - map_display_h * tile_h then
		map_y = map_h * tile_h - map_display_h * tile_h
	end
end

function love.draw()
	draw_map()
end