Python shadowcasting implementation

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Here's a Python implementation of Bjorn Bergstrom's excellent recursive shadowcasting FOV algorithm. I'm sure there's some optimization that could be done to it, but it might save you some time if you want to do a RL in Python.

This code runs in Windows using WCurses, and it should work on *nix with the standard curses module. It runs fine on my web hosting shell account via SSH.

"FOV calculation for roguelike"

import curses

FOV_RADIUS = 10

dungeon =  ["###########################################################",
            "#...........#.............................................#",
            "#...........#........#....................................#",
            "#.....................#...................................#",
            "#....####..............#..................................#",
            "#.......#.......................#####################.....#",
            "#.......#...........................................#.....#",
            "#.......#...........##..............................#.....#",
            "#####........#......##..........##################..#.....#",
            "#...#...........................#................#..#.....#",
            "#...#............#..............#................#..#.....#",
            "#...............................#..###############..#.....#",
            "#...............................#...................#.....#",
            "#...............................#...................#.....#",
            "#...............................#####################.....#",
            "#.........................................................#",
            "#.........................................................#",
            "###########################################################"]

class Map(object):
    # Multipliers for transforming coordinates to other octants:
    mult = [
                [1,  0,  0, -1, -1,  0,  0,  1],
                [0,  1, -1,  0,  0, -1,  1,  0],
                [0,  1,  1,  0,  0, -1, -1,  0],
                [1,  0,  0,  1, -1,  0,  0, -1]
            ]
    def __init__(self, map):
        self.data = map
        self.width, self.height = len(map[0]), len(map)
        self.light = []
        for i in range(self.height):
            self.light.append([0] * self.width)
        self.flag = 0
    def square(self, x, y):
        return self.data[y][x]
    def blocked(self, x, y):
        return (x < 0 or y < 0
                or x >= self.width or y >= self.height
                or self.data[y][x] == "#")
    def lit(self, x, y):
        return self.light[y][x] == self.flag
    def set_lit(self, x, y):
        if 0 <= x < self.width and 0 <= y < self.height:
            self.light[y][x] = self.flag
    def _cast_light(self, cx, cy, row, start, end, radius, xx, xy, yx, yy, id):
        "Recursive lightcasting function"
        if start < end:
            return
        radius_squared = radius*radius
        for j in range(row, radius+1):
            dx, dy = -j-1, -j
            blocked = False
            while dx <= 0:
                dx += 1
                # Translate the dx, dy coordinates into map coordinates:
                X, Y = cx + dx * xx + dy * xy, cy + dx * yx + dy * yy
                # l_slope and r_slope store the slopes of the left and right
                # extremities of the square we're considering:
                l_slope, r_slope = (dx-0.5)/(dy+0.5), (dx+0.5)/(dy-0.5)
                if start < r_slope:
                    continue
                elif end > l_slope:
                    break
                else:
                    # Our light beam is touching this square; light it:
                    if dx*dx + dy*dy < radius_squared:
                        self.set_lit(X, Y)
                    if blocked:
                        # we're scanning a row of blocked squares:
                        if self.blocked(X, Y):
                            new_start = r_slope
                            continue
                        else:
                            blocked = False
                            start = new_start
                    else:
                        if self.blocked(X, Y) and j < radius:
                            # This is a blocking square, start a child scan:
                            blocked = True
                            self._cast_light(cx, cy, j+1, start, l_slope,
                                             radius, xx, xy, yx, yy, id+1)
                            new_start = r_slope
            # Row is scanned; do next row unless last square was blocked:
            if blocked:
                break
    def do_fov(self, x, y, radius):
        "Calculate lit squares from the given location and radius"
        self.flag += 1
        for oct in range(8):
            self._cast_light(x, y, 1, 1.0, 0.0, radius,
                             self.mult[0][oct], self.mult[1][oct],
                             self.mult[2][oct], self.mult[3][oct], 0)
    def display(self, s, X, Y):
        "Display the map on the given curses screen (utterly unoptimized)"
        dark, lit = curses.color_pair(8), curses.color_pair(7) | curses.A_BOLD    
        for x in range(self.width):
            for y in range(self.height):
                if self.lit(x, y):
                    attr = lit
                else:
                    attr = dark
                if x == X and y == Y:
                    ch = '@'
                    attr = lit
                else:
                    ch = self.square(x, y)
                s.addstr(y, x, ch, attr)
        s.refresh()
        

def color_pairs():
    c = []
    for i in range(1, 16):
        curses.init_pair(i, i % 8, 0)
        if i < 8:
            c.append(curses.color_pair(i))
        else:
            c.append(curses.color_pair(i) | curses.A_BOLD)
    return c


if __name__ == '__main__':
    try:
        s = curses.initscr()
        curses.start_color()
        curses.noecho()
        curses.cbreak()
        color_pairs()
        s.keypad(1)
        x, y = 36, 13
        map = Map(dungeon)
        while True:
            map.do_fov(x, y, FOV_RADIUS)
            map.display(s, x, y)
            k = s.getch()
            if k == 27:
                break
            elif k == 259:
                y -= 1
            elif k == 258:
                y += 1
            elif k == 260:
                x -= 1
            elif k == 261:
                x += 1
    finally:
        s.keypad(0)
        curses.echo()
        curses.nocbreak()
        curses.endwin()
        print "Normal termination."
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