A-Star寻路

解释

A星寻路可以用来找到一种绕过障碍物从一个地点到另一个地点的方法。本例仅根据返回的坐标绘制路径。如果你想让敌人沿着这条路走，请参见 沿着一条路走的精灵 。

来源

astar_pathfinding.py

"""
A-Star Path-finding

Artwork from https://kenney.nl

If Python and Arcade are installed, this example can be run from the command line with:
python -m arcade.examples.astar_pathfinding
"""

import arcade
import random

SPRITE_IMAGE_SIZE = 128
SPRITE_SCALING = 0.25
SPRITE_SIZE = int(SPRITE_IMAGE_SIZE * SPRITE_SCALING)

SCREEN_WIDTH = 800
SCREEN_HEIGHT = 600
SCREEN_TITLE = "A-Star Path-finding"

MOVEMENT_SPEED = 5

VIEWPORT_MARGIN = 100


class MyGame(arcade.Window):
    """
    Main application class.
    """

    def __init__(self, width, height, title):
        """
        Initializer
        """

        # Call the parent class initializer
        super().__init__(width, height, title)

        # Variables that will hold sprite lists
        self.player_list = None
        self.wall_list = None
        self.enemy_list = None

        # Set up the player info
        self.player = None

        # Track the current state of what key is pressed
        self.left_pressed = False
        self.right_pressed = False
        self.up_pressed = False
        self.down_pressed = False

        self.physics_engine = None

        # --- Related to paths
        # List of points that makes up a path between two points
        self.path = None
        # List of points we checked to see if there is a barrier there
        self.barrier_list = None

        # Used in scrolling
        self.view_bottom = 0
        self.view_left = 0

        # Set the window background color
        self.background_color = arcade.color.AMAZON

    def setup(self):
        """ Set up the game and initialize the variables. """

        # Sprite lists
        self.player_list = arcade.SpriteList()
        self.wall_list = arcade.SpriteList(use_spatial_hash=True,
                                           spatial_hash_cell_size=128)
        self.enemy_list = arcade.SpriteList()

        # Set up the player
        resource = ":resources:images/animated_characters/" \
                   "female_person/femalePerson_idle.png"
        self.player = arcade.Sprite(resource, SPRITE_SCALING)
        self.player.center_x = SPRITE_SIZE * 5
        self.player.center_y = SPRITE_SIZE * 1
        self.player_list.append(self.player)

        # Set enemies
        resource = ":resources:images/animated_characters/zombie/zombie_idle.png"
        enemy = arcade.Sprite(resource, SPRITE_SCALING)
        enemy.center_x = SPRITE_SIZE * 4
        enemy.center_y = SPRITE_SIZE * 7
        self.enemy_list.append(enemy)

        spacing = SPRITE_SIZE * 3
        for column in range(10):
            for row in range(15):
                sprite = arcade.Sprite(":resources:images/tiles/grassCenter.png",
                                       SPRITE_SCALING)

                x = (column + 1) * spacing
                y = (row + 1) * sprite.height

                sprite.center_x = x
                sprite.center_y = y
                if random.randrange(100) > 30:
                    self.wall_list.append(sprite)

        self.physics_engine = arcade.PhysicsEngineSimple(self.player,
                                                         self.wall_list)

        # --- Path related
        # This variable holds the travel-path. We keep it as an attribute so
        # we can calculate it in on_update, and draw it in on_draw.
        self.path = None
        # Grid size for calculations. The smaller the grid, the longer the time
        # for calculations. Make sure the grid aligns with the sprite wall grid,
        # or some openings might be missed.
        grid_size = SPRITE_SIZE

        # Calculate the playing field size. We can't generate paths outside of
        # this.
        playing_field_left_boundary = -SPRITE_SIZE * 2
        playing_field_right_boundary = SPRITE_SIZE * 35
        playing_field_top_boundary = SPRITE_SIZE * 17
        playing_field_bottom_boundary = -SPRITE_SIZE * 2

        # This calculates a list of barriers. By calculating it here in the
        # init, we are assuming this list does not change. In this example,
        # our walls don't move, so that is ok. If we want moving barriers (such as
        # moving platforms or enemies) we need to recalculate. This can be an
        # time-intensive process depending on the playing field size and grid
        # resolution.

        # Note: If the enemy sprites are the same size, we only need to calculate
        # one of these. We do NOT need a different one for each enemy. The sprite
        # is just used for a size calculation.
        self.barrier_list = arcade.AStarBarrierList(enemy,
                                                    self.wall_list,
                                                    grid_size,
                                                    playing_field_left_boundary,
                                                    playing_field_right_boundary,
                                                    playing_field_bottom_boundary,
                                                    playing_field_top_boundary)

    def on_draw(self):
        """
        Render the screen.
        """
        # This command has to happen before we start drawing
        self.clear()

        # Draw all the sprites.
        self.player_list.draw()
        self.wall_list.draw()
        self.enemy_list.draw()

        if self.path:
            arcade.draw_line_strip(self.path, arcade.color.BLUE, 2)

    def on_update(self, delta_time):
        """ Movement and game logic """

        # Calculate speed based on the keys pressed
        self.player.change_x = 0
        self.player.change_y = 0

        if self.up_pressed and not self.down_pressed:
            self.player.change_y = MOVEMENT_SPEED
        elif self.down_pressed and not self.up_pressed:
            self.player.change_y = -MOVEMENT_SPEED
        if self.left_pressed and not self.right_pressed:
            self.player.change_x = -MOVEMENT_SPEED
        elif self.right_pressed and not self.left_pressed:
            self.player.change_x = MOVEMENT_SPEED

        # Update the character
        self.physics_engine.update()

        # Calculate a path to the player
        enemy = self.enemy_list[0]
        # Set to True if we can move diagonally. Note that diagonal movement
        # might cause the enemy to clip corners.
        self.path = arcade.astar_calculate_path(enemy.position,
                                                self.player.position,
                                                self.barrier_list,
                                                diagonal_movement=False)
        # print(self.path,"->", self.player.position)

        # --- Manage Scrolling ---

        # Keep track of if we changed the boundary. We don't want to call the
        # set_viewport command if we didn't change the view port.
        changed = False

        # Scroll left
        left_boundary = self.view_left + VIEWPORT_MARGIN
        if self.player.left < left_boundary:
            self.view_left -= left_boundary - self.player.left
            changed = True

        # Scroll right
        right_boundary = self.view_left + SCREEN_WIDTH - VIEWPORT_MARGIN
        if self.player.right > right_boundary:
            self.view_left += self.player.right - right_boundary
            changed = True

        # Scroll up
        top_boundary = self.view_bottom + SCREEN_HEIGHT - VIEWPORT_MARGIN
        if self.player.top > top_boundary:
            self.view_bottom += self.player.top - top_boundary
            changed = True

        # Scroll down
        bottom_boundary = self.view_bottom + VIEWPORT_MARGIN
        if self.player.bottom < bottom_boundary:
            self.view_bottom -= bottom_boundary - self.player.bottom
            changed = True

        # Make sure our boundaries are integer values. While the view port does
        # support floating point numbers, for this application we want every pixel
        # in the view port to map directly onto a pixel on the screen. We don't want
        # any rounding errors.
        self.view_left = int(self.view_left)
        self.view_bottom = int(self.view_bottom)

        # If we changed the boundary values, update the view port to match
        if changed:
            arcade.set_viewport(self.view_left,
                                SCREEN_WIDTH + self.view_left,
                                self.view_bottom,
                                SCREEN_HEIGHT + self.view_bottom)

    def on_key_press(self, key, modifiers):
        """Called whenever a key is pressed. """

        if key == arcade.key.UP:
            self.up_pressed = True
        elif key == arcade.key.DOWN:
            self.down_pressed = True
        elif key == arcade.key.LEFT:
            self.left_pressed = True
        elif key == arcade.key.RIGHT:
            self.right_pressed = True

    def on_key_release(self, key, modifiers):
        """Called when the user releases a key. """

        if key == arcade.key.UP:
            self.up_pressed = False
        elif key == arcade.key.DOWN:
            self.down_pressed = False
        elif key == arcade.key.LEFT:
            self.left_pressed = False
        elif key == arcade.key.RIGHT:
            self.right_pressed = False


def main():
    """ Main function """
    window = MyGame(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_TITLE)
    window.setup()
    arcade.run()


if __name__ == "__main__":
    main()