Complete Roguelike Tutorial, using python+libtcod, part 2

This is part of a series of tutorials; the main page can be found here.

The Dungeon

The Map

This part will introduce the map, FOV, and finally a neat dungeon generator! No roguelike is complete without those. We'll start with the map, a two-dimensional array of tiles where all your dungeon adventuring will happen. We'll start by defining its size at the top of the file. It's not quite the same size as the screen, to leave some space for a panel to show up later (where you can show stats and all). We'll try to make this as configurable as possible, this should suffice for now!

MAP_WIDTH = 80
MAP_HEIGHT = 45

Next, the tile colors. For now there are two tile types -- wall and ground. These will be their "dark" colors, which you'll see when they're not in FOV; their "lit" counterparts are not needed right now. Notice that their values are between 0 and 255, if you found colors on the web in hexadecimal format you'll have to convert them with a calculator. Finding RGB values by educated trial-and-error works at first but with time you'll have a set of colors that don't mix together very well (contrast and tone as perceived by the human eye, and all that stuff), so it's usually better to look at a chart of colors; just search for "html colors" and use one you like.

color_dark_wall = libtcod.Color(0, 0, 100)
color_dark_ground = libtcod.Color(50, 50, 150)

What sort of info will each tile hold? We'll start simple, with two values that say whether a tile is passable or not, and whether it blocks sight. In this case, it's better to seperate them early, so later you can have see-through but unpassable tiles such as chasms, or passable tiles that block sight for secret passages. They'll be defined in a Tile class, that we'll add to as we go. Believe me, this class will quickly grow to have about a dozen different values for each tile!

class Tile:
    #a tile of the map and its properties
    def __init__(self, blocked, block_sight = None):
        self.blocked = blocked
		
        #by default, if a tile is blocked, it also blocks sight
        if block_sight is None: block_sight = blocked
        self.block_sight = block_sight

As promised, the map is a two-dimensional array of tiles. The easiest way to do that is to have a list of rows, each row itself being a list of tiles, since there are no native multi-dimensional arrays in Python. We'll build it using a neat trick, list comprehensions. See, the usual way to build lists (from C++ land) is to create an empty list, then iterate with a for and add elements gradually. But in Python, the syntax [element for index in range], where index and range are the same as what you'd use in a for, will return a list of elements. Just take a second to understand that sentence if you never worked with that before. With two of those, one for rows and another for tiles in each row, we create the map in one fell swoop! The linked page has a ton of examples on that, and also an example of nested list comprehensions like we're using for the map. Well, that's an awful lot of words for such a tiny piece of code!

def make_map():
    global map
	
    #fill map with "unblocked" tiles
    map = [[ Tile(False)
        for y in range(MAP_HEIGHT) ]
            for x in range(MAP_WIDTH) ]

Accessing the tiles is as easy as map[x][y]. Here we add two pillars (blocked tiles) to demonstrate that, and provide a simple test.

    map[30][22].blocked = True
    map[30][22].block_sight = True
    map[50][22].blocked = True
    map[50][22].block_sight = True

Don't worry, we're already close to a playable version! Since we need to draw both the objects and the map, it now makes sense to put them all under a new function instead of directly in the main loop. Take the object rendering code to a new render_all function, and in its place (in the main loop) call render_all().

def render_all():
    #draw all objects in the list
    for object in objects:
        object.draw()

Still in the same function, we can now go through all the tiles and draw them to the screen, with the background color of a console character representing the corresponding tile. This will render the map.

    for y in range(MAP_HEIGHT):
        for x in range(MAP_WIDTH):
            wall = map[x][y].block_sight
            if wall:
                libtcod.console_set_back(0, x, y, color_dark_wall, libtcod.BKGND_SET )
            else:
                libtcod.console_set_back(0, x, y, color_dark_ground, libtcod.BKGND_SET )

Ok! Don't forget to call make_map() before the main loop, to set it up before the game begins. You should be able to see the two pillars and walk around the map now!

But wait, there's something wrong. The pillars show up, but the player can walk over them. That's easy to fix though, add this check to the beginning of the Object 's move method:

if not map[self.x + dx][self.y + dy].blocked:

Here's the code so far.

Field of View (FOV)

The next step towards a complete roguelike is FOV. This adds a tactical element and lets the player wonder what's on the other side of every door and every corner. The FOV works like a light source where the player stands, casting light in every direction but not getting past any walls. Regions in shadow are invisible. You could code it yourself by casting rays outward from the player, but it's much easier than that; libtcod has a whole module dedicated to it! It includes different methods with varying levels of precision, speed and other interesting properties. There's an [study here] if you want to know more about them, and how they compare against each other!

We'll define the algorithm along with the other constants so it can be changed later. For now it's 0, the default algorithm. There's also an option to light walls or not (ie, mark wall tiles as visible or not so you can show them in different colors), this is a matter of preference.

FOV_ALGO = 0  #default FOV algorithm
FOV_LIGHT_WALLS = True

Also, we'll need more colors for lit tiles! The color definitions will now be:

color_dark_wall = libtcod.Color(0, 0, 100)
color_light_wall = libtcod.Color(130, 110, 50)
color_dark_ground = libtcod.Color(50, 50, 150)
color_light_ground = libtcod.Color(200, 180, 50)

These are taken straight away from the libtcod sample that comes with the library, and you may want to change them to give your game a more unique feel (see the earlier notes about colors).

The libtcod FOV module needs to know which tiles block sight. So, we create a map that libtcod can understand (fov_map), and fill it with the appropriate values. They're taken from the tiles' own block_sight property. It also asks for a blocked value; this is completely irrelevant for FOV! It will be useful only for the pathfinding module, but it doesn't hurt to provide that value anyway.

fov_map = libtcod.map_new(MAP_WIDTH, MAP_HEIGHT)
for y in range(MAP_HEIGHT):
    for x in range(MAP_WIDTH):
        libtcod.map_set_properties(fov_map, x, y, not map[x][y].blocked, not map[x][y].block_sight)

FOV will only need to be recomputed if the player moves, or a tile changes. To model that we'll define a global variable fov_recompute = True before the main loop. Then, in the handle_keys function, whenever the player moves we set it to True again, like in the following code.

    #movement keys
    elif libtcod.console_is_key_pressed(libtcod.KEY_UP):
        player.move(0, -1)
        fov_recompute = True
        
    elif libtcod.console_is_key_pressed(libtcod.KEY_DOWN):
        player.move(0, 1)
        fov_recompute = True
        
    elif libtcod.console_is_key_pressed(libtcod.KEY_LEFT):
        player.move(-1, 0)
        fov_recompute = True
        
    elif libtcod.console_is_key_pressed(libtcod.KEY_RIGHT):
        player.move(1, 0)
        fov_recompute = True

Now we need to change the rendering code to actually recompute FOV, and display the result! It's a major overhaul of the render_all function.

Dungeon generator

The code includes a simple algorithm, it's just a sequence of rooms, each one connected to the next through a tunnel. The overlaps make it look more complex than may be apparent at first though.

Go on to the next part.